Retinoscopy

RETINOSCOPYBy Dr. Mohamed A.A Etarshawi

M.D Ophthalmology

HISTORY OF THE RETINOSCOPE

• The observations that led to clinical <retinoscopy> were made in 1859 with a plane mirror ophthalmoscope lighted by a candle, when Sir William Bowman noted a linear shadow seen when examining an astigmatic eye.

• By 1875, the optics were explained and the procedure was described as a “shadow test,” an allusion . إشارة .to neutralization. H إلماعParent coined the term <retinoscopy> in 1881

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• The earliest retinoscopes used a mirror to reflect a candle, which produced a “spot” of light. It was soon discovered that a linear streak of light could be produced with slit-shaped mirrors.

• Early electric retinoscopes used spiral filament bulbs and a rotating slit. Jacob Copeland introduced a linear filament bulb that produced a sharp, bright line of light. The Copeland streak retinoscope set the standard for future retinoscopic developments.

OPTICS OF THE RETINOSCOPE

• The streak retinoscope has supplanted يحل the spot retinoscope in the modern eye محلهclinic, and only the streak retinoscope is discussed in this chapter.

• Although the various brands ماركة of streak retinoscopes differ in design, they all work similarly. Light is produced by a luminous filament within the base of the handle and emanates from a mirror in the head as a linear streak, with both orientationتوجه ; and vergence إنحدار ، ميلcontrolled by the retinoscopist.


• The streak of light passes through the patient's tear film, cornea, anterior chamber, lens, vitreous chamber, and retina. It is then reflected from the choroid and retinal pigment epithelium as a linear red reflex that passes back through the sensory retina, vitreous, lens, aqueous, cornea, and tear film, through the air between the patient and the examiner, and into the head of the retinoscope, through an aperture in the mirror.


• Finally exiting through the back of the retinoscope into the retinoscopist's own eye.

• By observing qualities of the reflected light (the reflex) after it leaves the patient's eye, the retinoscopist can make determinations about the patient's refractive state.

streak retinoscope

Diagrammatic cross-section of streak retinoscope

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Diagrammatic cross-section of streak retinoscope.

• Light from the filament passes through the lens to the mirror, where it is reflected toward the patient. The examiner views through the aperture behind the mirror.

• The arrows represent the two controllable functions. The curved arrow indicates that the bulb may be rotated. The straight arrow indicates that the vergence of the light rays may be altered by changing the filament to lens distance.

• The filament is shown at the focal length of the lens so that parallel light rays emerge.


• Explaining the optics and proper usage of the retinoscope can be a confusing business. To help simplify the text, we have chosen to use the feminine. مؤنث pronouns (e.g., “she” and “her”) ضميرwhen referring to the retinoscopist, and the masculine ones (e.g., “he,” “him,” and “his”) when referring to the patient.

OPTICS OF THE RETINOSCOPE• All streak retinoscopes are made of the same

fundamental components: light source, condensing lens, mirror, and sleeve .

• The light source is a light bulb with a fine, linear filament, which projects a fine, linear streak of light with the passage of an electric current.

• The filament (therefore the streak), can be rotated 360 degrees by rotating the sleeve of the retinoscope. Currently, most retinoscopes use a halogen bulb, which projects a very bright streak.

OPTICS OF THE RETINOSCOPE• The condensing lens is a plus lens, which

exerts positive vergence on the streak, which is emitted from the point-source filament in a highly diverging manner.

• The position of the lens in relation to the light filament can be altered by raising or lowering the sleeve.

• In this way, the vergence of the streak that is emitted from the retinoscope can be controlled by the retinoscopist, as described subsequently.

OPTICS OF THE RETINOSCOPE• The mirror bends light that originates in the

handle and is initially projected upward toward the ceiling, to instead exit the retinoscope along an axis parallel to the floor so that it can be projected into the patient's eye. The mirror should not reflect 100% of visible light; rather, it must allow some light to pass through it.

• Only in this way can the retinoscopist have a view into the patient's pupil that is coaxial

المحور .to the path of the streak متحد

CONTROLLING THE PROPERTIES OF THE

RETINOSCOPE • The basic idea behind the retinoscope is that

the retinoscopist creates a streak of light, projects it into a patient's eye, bounces it off his retina, and makes deductions يرتد concerning the patient's refractive استنتاجstatus based on what the image of that streak looks like when it reaches the retinoscopist's eye. To aid her in this task, the retinoscopist has control over, and can easily vary, certain aspects of the system.

CONTROLLING THE PROPERTIES OF THE RETINOSCOPE

Two things she can control have nothing to do with the intrinsic properties of the

retinoscope she is holding: • The distance between the retinoscopist's

eye and the patient's (W.D). • Which lenses she may be holding between

the patient's eye and her own.


• Optical effects of moving the retinoscope bulb to change the filament to lens distance; this type of retinoscope emits convergent light when the sleeve is moved up. Note the vergences of the emerging rays:

• (left) concave mirror effect is produced when bulb is moved down;

• (right) plane mirror effect is produced when bulb is moved up.


Plane mirrorConcave mirror

Movement of the light source



However, two properties over which the retinoscopist has total control are completely

intrinsic to the retinoscope she is holding .• 1-The first is the orientation of the streak as

it leaves the retinoscope. Because the light source for the retinoscope is a fine filament, the light emanates from the retinoscope as a fine streak.


• By rotating the light source, the retinoscopist can easily alter the orientation of the streak by more than 360 degrees. Merely by rotating the sleeve on the handle of the retinoscope, she can project a streak whose orientation is parallel to the floor, or perpendicular to it, or any meridian in between.


• 2-The second property that can be controlled easily by the retinoscopist is the vergence of the incident streak. With the touch of a finger (or thumb), the retinoscopist can alter the streak so that it leaves the retinoscope as converging, diverging, or even parallel light. This feature gives the retinoscopist an incredible يصدق amount of power in الevaluating a patient's refractive state. Unfortunately, it is probably the most underused feature of the retinoscope.


• Changing the distance between the light filament and the condensing lens alters the vergence of the emitted streak. This can be accomplished by raising or lowering the sleeve in the handle of the retinoscope.

• This is the most fundamental way in which different models of retinoscope will contrast,

االختالف يتغاير and it is obviously important for the retinoscopist to be familiar with the type of retinoscope with which she is working.


• The condensing lens is fixed, and the light source can be raised or lowered by moving the sleeve up or down (Fig. 2).

• When the sleeve is raised in these retinoscopes, the streak emanates as a diverging beam; when the sleeve is lowered, the streak emanates in a converging nature , and therefore we use the term “sleeve up” when the retinoscope emits diverging light and “sleeve down” when it emits converging light.



By altering the vergence of the emitted streak, the retinoscopist is actually manipulating its focal point, the point where the emitted light comes

to focus in a point in real or virtual space .When in maximum convergence (sleeve up), that focal point is a real image located 33 cm in front of the retinoscope. (You can test this by moving the palm of your hand in front of the retinoscope at a distance of 33 cm, then turning

it on with the sleeve raised all the way up.

Figure 2concave mirrorplane mirror

Movement of the lens



• Optical effects of moving the lens to change the filament to lens distance; this type of retinoscope emits convergent light when the sleeve is moved up. Note the vergences of the emerging rays: (left) plane mirror effect when lens is moved down; (right) concave mirror effect when lens is moved up. 2

DETERMINING THE VERGENCE OF THE RETINOSCOPE BEAM Lecture 1

To determine the vergence of a retinoscope at any sleeve adjustment, a simple trick called Foucault's Method (Fig. 4) can be used. The most instructiveتثقيفي part of this exercise is shown in Figure 4A.

Note that when a card is introduced at the edge of a converging beam, an opposite movement is produced on a screen located beyond the focal point.



Figure 4

against” motion

with” motion

with” motion

Screen

Rays converging beyond screen

Diverging rays

Rays converging at a focal point before screen


Foucault's method for determining vergence of rays emerging from a retinoscope

• A card or your hand is introduced close to the retinoscope and moved at right angles to the emerging rays. Observe the shadow produced in the unfocused image on a screen or wall in a darkened room.

• (A) Rays converging at a focal point before screen cause an “against” motion.

• (B) Rays converging beyond screen cause a “with” motion.

• (C) Diverging rays cause a “with” motion.

• Foucault's method for determining vergence of rays emerging from a retinoscope. A card or your hand is introduced close to the retinoscope and moved at right angles to the emerging rays.

• Observe the shadow produced in the unfocused image on a screen or wall in a darkened room.

• A. Rays converging at a focal point before screen cause an “against” motion.

• B. Rays converging beyond screen cause a “with” motion.

• C. Diverging rays cause a “with” motion.

Calibration of the Converging Beam

Bring the sleeve all the way up and place it against a reflecting surface such as the wall. Move away from the wall and observe from the side (not through the peephole) until the streak is in sharp focus on the wall. You should note that when the retinoscope is moved beyond that distance, the streak will go out of focus because the filament light has converged and then diverged (see Fig. 4A

) .



• Return to the point of sharp focus and measure to determine the focal point of the retinoscope: it should be about 33 cm, which corresponds to + 3.00 D.

• Sit in the patient's examination chair and aim the retinoscope toward the distant wall while moving the sleeve up and down.

Calibration of the Parallel Beam

• Watch where the finest focused image of the filament is observed. Note the relative position of the bottom of the sleeve with regard to the range of sleeve movement.

• In that position, the retinoscope beam is as parallel as possible and it has no vergence and thus is focused at infinity.

NEUTRALIZATION RETINOSCOPY

Neutralization is performed with the retinoscope held at a constant predetermined distance from the patient with the sleeve all the way down (light emitted in a diverging manner). The retinoscopist makes decisions about the patient's refractive error based on the appearance of the retinoscope reflex after it is reflected off the patient's fundus and back

through the pupil) Fig. 16.(


NEUTRALIZATION RETINOSCOPY

• What the retinoscopist sees is not the image “on the retina” ,but rather the magnified image “of the retina.”

• Therefore, discussion about neutralization must begin with discussion about the retinoscopic reflex at neutralization.

THE NEUTRALIZATION REFLEX

• When performing neutralization the retinoscopist shines diverging light through the patient's pupil from a standard working distance (usually 66 cm).

• This light is reflected off the patient's fundus, and in this way, the fundus acts as a new point source of light. This is called the illuminating system.

THE NEUTRALIZATION REFLEX• The light that originates from the luminous

retina then passes through the patient's vitreous, lens, pupil, aqueous, and cornea, until it finally exits the patient's eye on its way back to the retinoscope. This is called the viewing system.

• The retinoscopist must be able to differentiate between the illuminating and viewing systems because different techniques of retinoscopy can depend on varying the components of one but not the other.

THE NEUTRALIZATION REFLEX• 1-When diverging light is shone onto an

emmetrope's retina, the retina becomes luminous and acts as a point source of light. The rays of light then escape his eye in a parallel fashion. If this concept is not intuitive, بدهي merely follow the standard light ray diagram backward.

• 2-In similar fashion, light starting as a point on a myope's luminous retina is emitted as converging light, where more myopic individuals emit more highly converging light than less myopic ones.

THE NEUTRALIZATION REFLEX• 3-Similarly, light starting as a point on a

hyperope's luminous retina is emitted as diverging light, and hyperopic patients emit more diverging light than less hyperopic ones.

• The vergence of the rays emitted from the eye determines the qualities of the reflex seen by the retinoscopist.

• A neutralization reflex occurs under the circumstance when the far point of the eye correlates نظامية بصورة with the يربطlocation of the peephole of the retinoscope

• If a retinoscopist were to examine an emmetropic eye at infinity, she could make assumptions افتراض on the diverging, converging, or parallel nature of the reflected light by sweeping the retinoscope streak back and forth across the patient's pupil.

• However, it is not possible to perform retinoscopy from an infinite distance; it is customary to adapt a working distance of 66 cm, corresponding to + 1.50 D.

• By introducing + 1.5 lens in front of the subject's eye, the far point of a plano prescription is relocated to 66 cm.

• In this circumstance, what the retinoscopist is truly evaluating is whether the :-retinoscope lies between the patient's eye and far point, lies at the far point, or lies beyond it.

1. If the patient is an emmetrope, the far point lies on the horizon, and therefore the retinoscope always must lie between the patient's eye and far point.

2. If the patient is a hyperope, the far point actually lies beyond the horizon, and the retinoscope also lies between the patient's eye and far point.

FP

FP

3-Things are more interesting, however, when evaluating myopes in this way.

Light is emitted from a myope in a converging manner so that the far point is somewhere in real space (finite) in front of the myope's eye. It is possible for the retinoscope to be placed

A- between the patient and far point ,B-exactly on the far point, or C-out beyond the far point.

THE NEUTRALIZATION REFLEX

This relationship depends, of course, on both the location of the retinoscope (W.D), and the level of myopia (which determines the location of the far point).

ABC

• If the retinoscope is placed between the eye and far point (as it is for all emmetropes and hyperopes, and some myopes) and turned so that the emitted streak is swept from side to side across the patient's pupil, the light reflex seen inside the pupil appears to sweep in the same direction as the light emitted from the retinoscope (seen on the patient's iris, lids, brow, and cheek).

• This motion is called “with” motion because the light that is afferent to the retinoscope seems to move “with” the light that is efferent from the retinoscope

THE NEUTRALIZATION REFLEX• Fig. 17. The optical basis for neutralization <

retinoscopy>. The location of far points produces the “with” and “against” motions for a retinoscope with a divergent beam when performing neutralization retinoscopy. “With” motion is seen under all circumstances except when the far point of the eye-corrective lens system is situated between the cornea and the peephole ثقب of the retinoscope. The far point of the illustrated eye is at the peephole and is thus neutralized.



Figure 17


Lecture 2 With” motion reflex in

hyperopia


Fig. 18. “With” motion reflex in hyperopia

A “with motion” reflex of light comes into the shadow projected in the optical system from the aperture of the retinoscope or the examiner's pupil.

The rays from the filament to the retina are not shown. They form an unfocused horizontal filament image on the retina of the patient that acts as a new object with its image behind the retina.

When the retinoscope is tilted slightly, the object (RETINA) moves down and the image (REFLEX) moves down and vise versa. This is seen as a “with motion” reflex.

Figure 19 against motion reflex of myopia

• If the retinoscope is placed beyond the patient's far point and swept from side to side across the pupil, the light reflex (efferent) seen inside the pupil appears to sweep in the opposite direction as the streak emitted from the retinoscope (afferent )

Fig. 19• This motion is called “against” motion because

the light emitted from the eye (efferent) appears to move “against” the light that is emitted directly from the retinoscope (afferent (.




Fig. 19. Origin of the “against” movement in myopia


“On-off” phenomenon• When the retinoscope is placed exactly on the

patient's far point, neither “with” nor “against” motion is seen. At this point, all the light emitted from the patient's eye enters the retinoscopist's eye simultaneously.

• At exact neutrality, in a spherical eye with a small pupil, the retinoscopist may see no motion at all; rather, the patient's pupil seems to suddenly fill with light as the streak moves across it.

• This is obtained in myopic eye exactly reciprocal to W.D in diopters.

• This “on-off” phenomenon is important to recognize because it serves as the end point when performing the technique of neutralization.

Other qualities of the reflex

• In addition to its direction of movement, other qualities of the reflected retinoscope streak can be evaluated. These qualities all give the retinoscopist clues as to how close to the far point the retinoscope is being held.

The three most important qualities of the reflex are:

1. the speed at which it moves,2. its brightness, 3. its width.


If one thinks of the reflex at the neutralization point as :

• infinitely fast (so fast that it immediately fills the pupil without apparent motion),

• infinitely ; له حد ال محدود bright, and غير• infinitely wide, it is easy to understand

what the reflex should look like when the retinoscope is either near to, or far from, the neutralization point Fig. 20




qualities of the reflex

• When the retinoscope is held near the patient's far point, the reflex should appear fairly fast, bright, and wide.

• As the retinoscope is moved farther from the far point, the reflex appears to move slower and is dimmer and thinner.

• The retinoscope can eventually be moved so far from the patient's far point that the reflex is slow, wide, and dim enough that it is quite difficult to recognize as a reflex at all.


• Fig. 20 .Neutralization retinoscopy diagram of changes in characteristics of reflex as in the zone surrounding the point of neutrality.

• At neutrality, the reflex motion may be so fast that it cannot be detected. The end point or end zone should be approached from the “with” reflex side and the judgment of neutrality made erring . يزل يخطئtoward the “with” reflex rather than the “against” reflex.

• The neutral point lies within the neutralization zone where neutralization is best observed. (

Figure 20

Fig_ 20.htm

Optics of the Neutralization Reflex

• Five features characterize the neutralization end point, the point at which neither a “with” nor “against” reflex can be identified. Three of these are considered to define the end point, but two others can also be observed. The three standard characteristics are :

• Increases in speed, brightness, and width of the moving image. )1,2 &3 )

• To these can be added : the “on-off phenomenon” (the intermittent disappearance of the observed reflex) and the scissors reflex) .4 &5 (


1-Speed of the “with” or “against” motion:• If the retinoscope mirror is tilted in a highly

ametropic eye, the resultant reflex is (more rapid ) imaged at a far point that is much closer to the eye than the reflex of an almost emmetropic eye, the far point of which is located at a much greater distance.

• With regard to the subject's pupil, movement of the image at the far point of the almost emmetropic eye will seem to have a greater angular velocity or speed.


• It should be stressed that the direction of movement of the fundus image is not influenced by the patient's ametropia ( illuminating system).

• The “with” or “against” movement is a function of the observation (VIEWING) system, thus an “against” movement occurs only when the eye and external lens system have a far point lying between the patient's eye and the retinoscope peephole )High myopia)


2-Brightness of the image: • As neutrality is approached, all of the rays

emerging from the patient’s eye are focused at the peephole, where they provide the brightest image that the examiner observes. Illumination increases inversely to the square of image size.

• At any other focal distance, some or all of the rays of light will not reach the peephole and the image becomes duller Fig. 21




3-Width of reflex• In general, the width of the streak reflex and the

apparent speed of the streak reflex as it moves across the pupil give an indication of how far you are from neutrality.

• Young eyes that are not diseased and have not had surgery give the most defined reflexes. Corneal diseases, cataracts, IOLs, hazy posterior capsules, and cloudiness in the vitreous distort the reflexes and change the "rules" of appearance.

• Sometimes width and speed do not give reliable clues and you must just rely on apparent with-motion to arrive at the best retinoscopic estimate.

A very wide (almost filling the pupil), slow moving streak reflex indicates that you are a long way from neutrality. For instance, the with or against reflex you would see at plano when streaking a (– or +5.00 hyperope.(

As we add plus sphere power the streak tends to narrow and speed up in its apparent motion.

3-Width of reflex

As we continue adding plus sphere power and approachتقريبا neutrality, the streak widens again and speeds up even more.

3-Width of reflex

At neutrality the streak reflex widens more to completely fill the pupil.

3-Width of reflex

3-Width of reflex

In astigmatism :Streaking one meridian gives you against- motion, and streaking the meridian 90 degrees away gives you with- motion.

• Streaking one meridian gives you with-motion (or against- motion) with a wide streak reflex, and streaking the meridian 90 degrees away gives you the same motion but with a narrower streak reflex.

3-Width of reflex

a wide streak reflex,narrower streak reflex

3-Width of reflex

• As we add plus sphere power, the reflex at 90 narrows and the reflex at 180 quickly widens and reaches neutrality.


4-The on-off phenomenon: Although the retinoscopic reflex is bright and wide on either side of neutrality, the reflex may disappear completely when the retinoscope peephole is exactly conjugate to the eye-corrective lens system i.e far point of the examined eye. (see Fig. 21 (.

• Fortunately, neither the patient's eye nor the examiner's eye and hand can maintain this exact position for long, but astute ذكي retinoscopist may notice the on-off phenomenon at neutrality.





• Fig. 21. The origin of the on-off phenomenon at neutrality. The far point of the eye is situated at the peephole of the retinoscope. Either all or none of the rays will pass through the peephole with the slightest shift in the subject's eye or the retinoscope or the retinoscopist's eye, causing the retinoscopist to see the contents of the pupil as either filled with light or black.

Fig. 21 the on-off phenomenon at neutrality

Patient’s eye

Optics of the Neutralization Reflex Lecture 3

5-The scissors reflex: The refractive elements of the eye are not perfectly spherical. Thus, the center of the optical path may be slightly myopic

when compared with that of the periphery .The amount of aberration may be small, but under circumstances of perfect neutralization and a widely dilated pupil, the center of the optical path may return a “with” motion while the periphery

returns an “against” motion.


• This pattern of opposing central and peripheral retinoscopic movements is known as a scissors reflex. There is only a small dioptric distance over which the scissors reflex can be detected. The entire reflex returns to all “with” or all “against” motion within about 0.50 D on either side of neutralization). narrow zone)

Estimating Low Myopes via Neutralization Without Lenses

• By now the reader should have determined that it is in fact quite possible to neutralize low myopes without the use of lenses.

• The trick is to place the retinoscope directly on the patient's far point, sweep the retinoscope streak across the patient's pupil with the sleeve down, recognize the “on-off” phenomenon of the neutralization reflex, measure the distance from the patient's eye to the retinoscope in meters, take the reciprocal—thus converting from meters (distance) to diopters (vergence)—and the patient's refractive error has been determined.

Neutralization Without Lenses• For example, neutralization for a -2.00-D myope

can be seen by placing the retinoscope 50 cm from the patient's eye, and for a -4.00-D myope by placing the retinoscope 25 cm from this patient's eye (without considering a certain W.D(

• Neutralization for an emmetrope can only be done in this fashion by placing the retinoscope infinitely far from the patient's eye—theoretically possible, but not practically feasible. . مالئم عملي

NEUTRALIZATION Without Lenses• Because the far points of hyperopes do not lie in

real space (they lie beyond infinity), hyperopes cannot be neutralized in this way.

• The aforementioned technique describes a way to estimate a low myope's refractive error without the use of lenses.

• The key to this method is that the retinoscopist must change the distance that the retinoscope is held from the patient's eye when trying to find the far point.

Performing neutralization• When performing neutralization she does exactly

the opposite—she holds the retinoscope at a constant specific working distance and uses lenses to bring the patient's far point to the retinoscope.

• The first thing that a retinoscopist must do is choose a comfortable working distance. She wants to be as far from her patient as possible while still being close enough to comfortably manipulate lenses in front of his eye. Thus, the working distance usually is described as “arms length” away from the patient.

Performing neutralization

• For the average retinoscopist, this distance works out to about 66 cm. Taller retinoscopists may prefer 75 cm, whereas shorter ones may use 50 cm.

• It is not uncommon for retinoscopists to work closer than their usual working distance in difficult cases, such as small children, or adults with cataracts or small pupils.

• The actual working distance does not matter as long the retinoscopist is aware of the distance and adjusts her calculations accordingly.

Performing neutralization of against” motion

• The retinoscopist should be able to sit at her comfortable working distance while using lenses to bring the patient's far point to her.

• The retinoscopist accomplishes this feat . عمل فذ by sweeping the retinoscope streakعمل

across the patient's pupil and evaluating the direction, speed, brightness, and width of the reflex.

• If she observes “against” motion, the retinoscope must lie beyond the patient's far point, and the retinoscopist can move the far point toward the retinoscope by placing a minus lens in front of her patient's eye.




• If the reflex is fast, bright, and wide, the retinoscope must have been near to the patient's far point, and a weak minus lens should be chosen.

• However, if the reflex is slow, dim, and narrow, the retinoscope probably lies a greater distance from the far point, and a stronger minus lens should be chosen.

• If “with” motion is observed after a minus lens is placed before the patient's eye, the patient's far point has been moved beyond the retinoscope because too strong of a minus lens was chosen. This lens should be removed and replaced with a weaker minus one.

Performing neutralization of “with” motion

• Similar manipulations are performed if “with” motion is initially seen when neutralization is begun. In such cases, the far point must lie beyond the retinoscopist's comfortable working distance.

• Again, how far away the far point lies can be estimated by judging the quality of the reflex.

• A plus lens then is chosen to bring the far point forward toward the retinoscope.

Performing neutralization of “with” motion

• Whenever possible, the retinoscopist should try to manipulate the far point in such a way that “with” motion is being observed.

• A “with” reflex typically is sharper and easier to judge than an “against” reflex. Thus, if “against” motion is seen, neutralization will be easier to perform if a strong enough minus lens is placed to push the far point beyond the retinoscope, so that the retinoscopist can observe “with” motion.

minus lenses in front of younger patients can excite accommodation

• Care must always be taken, however, when putting minus lenses in front of younger patients because they can easily “eat up” this minus by accommodating, thus leading the less careful retinoscopist down the wrong path.

• It should also be noted that the neutralization end point is not exactly an end point—rather it is an end zone that measures about half a diopter in depth (see Fig. 20(




“zone of doubt” varies with pupil size and working distance

• The true size of this “zone of doubt” varies with pupil size and working distance —it is narrowest with a small pupil and close working distance.

• Best results are achieved when entering the zone of doubt from the plus side, by watching the “with” motion reflex get faster, brighter, and wider until the retinoscopist is convinced the neutralization reflex has been achieved.

• If the zone of doubt is entered from the minus side (through “against” motion), there is a greater chance for error.

The neutralization reflex

• Eventually, after just a few different lenses are placed before the patient's eye, the retinoscopist can observe the neutralization reflex.

• At this point the goal is achieved, and the retinoscopist has managed to bring the patient's far point to the retinoscope (which is being held at the working distance).

• The retinoscopist is now ready to write a spectacle correction )؛ prescription(.

CORRECTING THE PRESCRIPTION FOR THE WORKING DISTANCE LENS

• However, the lenses currently in front of the patient's eye do not represent the correction needed to see clearly at infinite distance; rather, the lenses represent the correction needed to see clearly at 66 cm.

• The patient will be quite dissatisfied غير if given a prescription for a pair of راضglasses that allows for clear vision only 66 cm away or closer.


• The retinoscopist must always remember to modify the prescription for distance vision, a mathematical manipulation called correcting for the working distance.

• The gross power is that which the retinoscopist is holding when retinoscopy is completed.

• This corresponds to the power that brings light from the patient's luminous retina to focus at the working distance ( on the peephole of the retinoscope(.


• The net power is that which neutralizes the patient's refractive error for good distance vision—the power that focuses light from the luminous retina of the patient to a point at the horizon. )His far point must be at infinity after full correction).


• The mathematical computation ; احتساب is إحصاءsimple. The retinoscopist merely subtracts the working distance (in diopters) from the gross to get the net power.

• For example, when the working distance is 66 cm 1.50 +)= D) and the patient is neutralized with a

• -2.5 D. lens, the gross power minus the working distance equals the net power,

or: -2.5 - (+ 1.5) = - 4D. • The retinoscopist will give a prescription for a - 4D.

lens. The previous discussion describes neutralization of spherical patients.

NEUTRALIZATION OF ASTIGMATIC EYES

• In patients with astigmatism, the reflex seen in the pupil has one more quality in addition to speed, brightness, and width. The reflex in patients with astigmatism also appears to “break” as the light filament is rotated Fig. 22. The retinoscope reflex seen in the patient's pupil will not be continuous with the streak lying on the cornea, lids, forehead, and cheek; it will appear broken.

• There will be, however, two meridians where the retinoscope reflex will be continuous with the streak—where it will not appear broken.


• These meridians correspond to the two axes of the patient's astigmatism. The retinoscopist merely needs to neutralize these two meridians separately and combine them to come up with the desired spectacle correction

• This can be done using only spherical lenses (as is best when neutralizing children with loose lenses), spherical and plus cylindrical lenses (using a plus cylinder phoropter or loose lenses and trial frames), or spherical and minus cylindrical lenses (using a minus cylinder phoropter or loose lenses and trial frames).


• Let us further explore the methods of neutralizing astigmatic individuals in whom the less plus (or more minus) axis is neutralized first and the more plus (or less minus) axis is neutralized second.

• When neutralizing the axes in this order, the retinoscopist can use either only spherical lenses, or spherical and plus cylindrical lenses.

Fig. 22.phenomenon Break

The line between the streak in the pupil and outside the pupil is broken when the streak is off the correct axis. (

BREAK PHENOMENON• Astigmatism can also be detected by

observation of the break phenomenon. It is useful in refining the axis of large astigmatic cylinders because one can observe a discontinuity, or “break,” between the enhanced intercept axis and that of the retinal reflex when the retinoscope filament beam is rotated somewhat away from the correct cylinder axis (see Fig. 22).


• Procedure for neutralizing an astigmatic eye• 1. The first step is to neutralize one of the meridians.

You will be adding plus sphere power and streaking each of the primary meridians after each power change.

• The meridian with the narrow, fast reflex will neutralize first. This meridian will be 90 degrees away from the meridian with the widest, slowest streak reflex.

• In this example, the 180 degree( right one ) meridian will neutralize first.

As we add plus sphere power, the reflex at 90(left ) narrows and the reflex at 180 (right ) quickly widens and reaches neutral point.

Procedure for neutralizing an astigmatic eye

• 2. The next step is to confirm/identify the axis of the astigmatism. We have a good idea of what the axis is from the neutralization process. There are several clues that we can use:

A. The Thickness Phenomenon B. The Intensity Phenomenon C. The Break and Skew

Phenomena D. Straddling the Axis


The Thickness Phenomenon:

The streak reflex appears to be narrowest ( left ) when we are streaking the meridian of the correct axis.

As you move away from the correct axis, the streak reflex becomes wider ( right ).


Procedure for neutralizing of an astigmatic eye

• The Intensity PhenomenonThe streak reflex appears brightest

when you are streaking the meridian of the correct axis.

As you move away from the correct axis, the streak reflex becomes more dim (less bright ).

The skew phenomenon: If we streak a meridian that is away from the

meridian of the correct axis, the reflex will tend to travel along the correct meridian rather than follow the streak. This guides us back to the correct meridian.

The skew phenomenonThe skew phenomenon

Correct axis


• Straddling the Axis Assuming that there is regular astigmatism present,

when one meridian has been neutralized, the meridian exactly 90 degrees away will have the strongest, most defined with- motion reflex.


• The axis can be confirmed by streaking the meridians 45 degrees to each side of what we believe to be the meridian of

the correct axis .In this case we believe that streaking the 90 degree meridian gives the most

defined reflex .We streak the 45 degree meridian and the streak reflex widens and degrades in

sharpness .The same thing happens when we streak the 135 degree meridian. This confirms

90 degrees as the correct meridian .45 degrees

135 degrees

Straddling the Axis


STRADDLINGWhen the cylinder power is weak, straddling reveals an initial incorrect estimate of the axis location.

The thinner image is called the “guide” because it guides us to adjust the plus-cylinder axis toward the thinner image.

This step provides the initial detection of astigmatism, and the phoropter axis can be adjusted so that plus lenses can be dialed into place along the enhanced meridian.

Straddling• The straddling meridians are 45 degrees off

the glass axis, at roughly 35 and 125 degrees. As you move back from the eye while comparing meridians, the reflex at 125 degrees remains narrow (A) at the same distance that the reflex at 35 degrees has become wide (B). This dissimilarity indicates axis error; the narrow reflex (A) is the guide toward which we must turn the glass axis.


• If the reflex in one of the straddle meridians is narrower than the reflex in the other straddle meridian, then we would adjust our estimated axis in the direction of the straddle meridian with the narrower reflex (guide).

• We would retest 45 degrees to each side of the new axis to confirm that the reflex in each straddle meridian is equally wide.

26


Spherical Lens Technique

• The first step is for the retinoscopist to find the least plus axis. The retinoscope streak is swept back and forth across the pupil while it is rotated 360 degrees by rotating the light filament in the handle.

• The retinoscopist then observes at which two meridians the retinoscope reflex does not appear broken—in cases of regular astigmatism, these two meridians should be 90 degrees apart.

Spherical Lens Technique• The retinoscopist then compares the reflex in one

meridian to the reflex in the other, noting which meridian's streak exhibits more “against” (slower,, broader , dimmer) or less “with” (faster, thinner, brighter) qualities than the other.

• The second meridian is neutralized first. If the reflex in one meridian shows “with” motion and in the other shows “against” motion, the meridian with the reflex that shows “with” is neutralized first

• The more minus meridian of the astigmatic person is then merely neutralized (second ) much as the spherical myope or hyperope described previously.

• The axis of the streak is held along the meridian line and swept in a direction perpendicular to it i.e (if the 90-degree axis is being neutralized, the streak is oriented straight up and down and swept from side to side) perpendicular to 90 degrees.

Spherical Lens Technique

Spherical Lens Technique• At first, it is not intuitive that the streak be held in

the same orientation as the axis meridian because one is searching for the power of the astigmatism, and the power lies not along the axis, but perpendicular to it.

• Here the retinoscopist must remember that the power is found not by holding the streak still (fixed ) , but rather by sweeping (moving ) it across the pupil.

• The retinoscope streak is rotated 90 degrees, and the reflex is re-examined.

Spherical Lens Technique• The reflex should not appear broken in the

new meridian—a broken reflex signifies that either the retinoscope streak is not exactly aligned along the patient's second axis or that the patient has irregular astigmatism.

• If the reflex is not broken, it is neutralized with spherical lenses. If spherical lenses are to be used, the second meridian is neutralized in exactly the same manner as the first after removal of the lenses used before and starting a new steps to neutralize the other meridian also with spherical lenses .

Spherical Lens Technique• Once the neutralization reflex has been

found in the second meridian, the retinoscopist again subtracts the working distance from the power in the 2 meridians and records the lens power needed to correct the patient for each particular axis. The difference in power of lenses between the 2 meridians is considered astigmatism.

Spherical Lens Technique• A simple conversion then needs to be performed before

presenting the patient with the proper spectacle prescription, as follows:

• Q: A patient is neutralized with the following lenses at a working distance of 66 cm: [+ 3.50 axis 90] and

[+ 4.25 axis 180]. What is the eyeglasses prescription? A: Step 1: Subtract the working distance. In this case,

the working distance is 66 cm, which is equal to 1.50 D:[+ 3.50 axis 90] - 1.50 = + 2.00 axis 90

[+ 4.25 axis 180] - 1.50 = + 2.75 axis 180 Step 2: Transpose from cross-cylinder notation to plus-cylinder notation:+ 2.00 sphere + ([+ 2.75 - 2.00] axis 180)

Objective prescription = +2.0 DS+ 0.75 DC x 180

Plus-Cylinder Technique• If the second meridian is to be neutralized

with a plus-cylinder lens (as is done with a plus-cylinder phoropter or loose lenses and trial frames), the first spherical lens should be left in the phoropter or trial frames.Keeping the spherical lenses in place. The axis of the cylindrical lens is oriented in the direction of the axis of the streak for the second meridian.

Plus-Cylinder Technique• Because a cylinder lens is being used, no

power is being added along the axis of the second meridian (which, of course, corresponds to the power of the first meridian).

• When the neutralization reflex is found for the second meridian, the streak is rotated 90 degrees to ensure that the first meridian is still neutralized.

Plus-Cylinder Technique• The working distance is then subtracted from the

spherical lens only, and the spectacle prescription is easily determined as follows:

• Q: A patient is neutralized with the following lenses at a working distance of 66 cm: [+ 3.50 sphere] and

[+ 0.75 axis 180]. What is the eyeglasses prescription?• A: Step 1: Subtract the working distance from the

spherical lens only. In this case, the working distance is 66 cm, which is equal to 1.50 D:[+ 3.50 sphere] - 1.50 = + 2.00 sphere Step 2: Add the cylindrical lens to the new power of the spherical lens:+ 2.00 sphere + [+ 0.75 axis 180]Objective prescription= 2.00 + DS + 0.75 DC x180

Minus-Cylinder Technique

• Some clinicians prefer to work in minus cylinder, patients are neutralized in the same aforementioned manner, except that the more “with” or less “against” meridian is neutralized first with spherical lenses.

• Then the less “with” or more “against” meridian is neutralized with a minus-cylinder in much the same way as the previous example used a plus-cylinder lens.

• The transposition is done as follows:

Minus-Cylinder Technique• Q: A patient is neutralized with the following

lenses at a working distance of 66 cm: [+ 4.25 sphere] and [-0.75 axis 90]. What is the eyeglasses prescription? A: Step 1: Subtract the working distance from the spherical lens only. In this case, the working distance is 66 cm, which is equal to 1.50 D:)+ 4.25 -1.50 (= + 2.75 sphere Step 2: Add the minus cylindrical lens to the new power of the spherical lens:

• + 2.75 sphere + (-0.75 axis 90( 90 × 0.75 - 2.75 + =

The next step is to neutralize the astigmatism (with minus-cylinder power).

Remember that one meridian has already been neutralized. The meridian 90 degrees away still has with-motion. We begin by streaking this meridian that has the brightest, narrowest with-reflex.

Since we are using a minus-cylinder lens, we will line up our cylinder axis perpendicular to the orientation of the streak. In other words, at 90 degrees in this example. We are streaking the 90 degree meridian, and the axis of the correcting minus-cylinder will be 90 degrees.

Once we have a neutral reflex, we have reached the endpoint. Neutrality can be assumed when any with-motion just disappears. This is preferable to relying on recognizing a neutral reflex, because the reflex may appear neutral over a wide range of power settings.

The final step is to subtract for our working distance. Lecture 6

• This is usually 1.50 D and it is subtracted from the sphere power only. Suppose our phoropter reads

• -1.00-150x90 when we have finished neutralizing the astigmatic meridian.

• We then would subtract 1.50 D sphere power for a final retinoscopic estimate of -2.50-1.50x90.

• It is easiest to practice retinoscopy on younger adults, ages 20 to 50. They usually have clear media, relatively relaxed accommodation, and a definite refractometric endpoint with which to compare your retinoscopy.

RELIABILITY الموثوقيةBecause important therapeutic judgments may

depend on the retinoscopic measurements, it is necessary to know how reliable these measurements are. Reliability and precision

إحكام . . ضبط are terms that describeدقةthe degree to which repeated measurements resemble one another. For example, five repeated measurements for one patient might yield the following five spherical results: + 2.25, + 2.75, + 2.50, + 2.75, + 2.25.

RELIABILITY الموثوقية• With another examiner, the following values

might be found: + 1.75, + 2.50, + 3.25, + 2.75, + 2.25. The first examiner displays أبرز ; أبدىa higher degree of reliability or precision than the second one. Nevertheless, the average value is the same for both: + 2.50.

• If any single measurements had been accepted as the patient's true refractive error, the patient might have been misjudged by only ¼D by the first examiner, but by as much as ¾D by the second.

RELIABILITY الموثوقية• How is it possible, then, to judge the

reliability of any measurement? The answer is straightforward: There must be repeated measurements so that the variability of the measurements can be assessed.

• The repeated measurements should be independent of one another, each derived without the measurer having knowledge of what the preceding ones were.

RELIABILITY الموثوقية• These are usually called “replicate ;طوى

measurements,” and there is no way to ثنىjudge reliability without them. In clinical practice, we often do these replicate measurements informally and almost intuitively.

• Fluctuations in the measurement process are unavoidable; statisticians call them “error.”

• The second examiner in the previous example is less precise than the first. She showed greater variability and larger error.

Reliability• Reliability and error for retinoscopy have

been evaluated. One study by Safir and coworkers entailed five clinicians performing retinoscopy on ten healthy young subjects on two separate occasions separated by one to three weeks. Results showed a 50% probability that the two measurements of spherical power would differ by 0.40 D.

• The Safir study also showed a threefold difference in reliability among retinoscopists.

Accuracy• Accuracy is another concept that is

important in the understanding of measurement.

• Accurate measurements are those that are close to the “true” value being measured. Accuracy is a relative conceptمفهوم

• One procedure may be more or less accurate than another.

• Suppose, for example, that a subject's true spherical refractive error were 2.00 D, and that ophthalmologist A measured it five times as 2.25, 2.25, 2.00, 2.00, 1.75, whereas ophthalmologist B got values of 2.5, 2.5, 2.75, 2.75, and 3. It is apparent that the method of ophthalmologist A is more accurate than that of ophthalmologist B.

• The typical measurement for ophthalmologist A is closer to the quantity sought than that of ophthalmologist B, even though the precision . ضبط of the two دقةrefractionists is about the same. This example shows that there is no predefined relationship between precision and accuracy.

THE ROLE OF THE RETINOSCOPE IN A MODERN EYE CLINIC-Autorefraction

• In the 21st century, we are faced with an ever-more automated world, and the ophthalmic practice has paralleled this move toward automation. اآللى أو األتوماتى التشغيل

• The retinoscope, really little more than a light filament, lens, and mirror, is now joined by many more sophisticated (and certainly more expensive) devices developed to help us obtain information regarding the refractive state of our patients.


• One family of such instruments consists of the automated refractors—tabletop or hand-held devices that perform an objective refraction in a matter of seconds at the touch of a button.

• The largest advantage of the automated refractor is that clinic personnel مجموع who have almost no knowledge الموظفينin the art of refraction can use it. For the average patient, automated refractors are reasonably accurate when compared with the retinoscope and generally agree within ½ D.

• Autorefraction• If automated refractors errيخطئ , they tend

to overestimate minus sphere by a fraction of a diopter. This discrepancy . تناقض تعارضprobably stems from the fact that patients accommodate in response to their sense that the automated refractor is at a closer distance to the patient than is the 6 meter far point used in retinoscopy. This is true even though the devices are designed to relax accommodation while fixing on an artificial distant target.

Autorefraction

• Where the automated refractor is at an undeniable اليجحد . ال disadvantage to the retinoscope is in ينكر

evaluating patients with irregular astigmatism, either from pathology (e.g., keratoconus, pellucid marginal degeneration) or postsurgically (e.g., corneal transplant, laser in situ keratomileusis [LASIK]). All the automated refractor operator can do is press a button while having the patient fixate on the target.

• The automated refractor then either calculates a “best fit” refraction or flashes an error message that there too much irregular astigmatism exists to make a reading.( Over cylinder)

Autorefraction

• The retinoscopist, however, can gain much more information about the refractive state of the patient by judging the quality of the light reflex observed in the patient's pupil.

• A skilled retinoscopist usually can deduce quantities and qualities of astigmatism in patients for whom the automated refractor fails. This is especially true in patients with poor best-corrected visual acuity.

• Other instruments that must be compared with the retinoscope are the keratoscope and the automated corneal modeling systems. Although it is tempting to compare these instruments with the retinoscope because they each provide important information regarding astigmatism,

Autorefraction

• it must be remembered that these instruments serve different purposes within the ophthalmic practice. The keratoscope and corneal topographers are used to evaluate corneal astigmatism only.

• The retinoscope, however, is used to determine the entire refractive state of the eye. These instruments all have their place and can complementتكملة each other well.


• A final issue, one that is becoming more important with every passing year, is the role of the retinoscope in managing the refractive surgery patient. Few studies address this problem. Retinoscopy has been shown to be accurate in evaluating the postoperative patient. Anecdotally, ; أفكوهة we أطروفةagree with these results. In our practice, we rely heavily on retinoscopy in evaluating pre- and postoperative refractive surgery patients.


• We believe that automated refractors cannot accurately evaluate the refractive state of someone with a surgically altered cornea and therefore believe that they have no role in providing data on these patients.

• Other studies have shown that corneal topography alone is not adequate in evaluating patient satisfaction after laser refractive surgery.


• Remembering that the critical zone of the retinoscopy reflex is the central 3 mm, and that the average excimer laser ablation diameter is 6 mm, one can see that the retinoscope is well suited to evaluate these patients.

• When patients who had previously had corneal refractive surgery subsequently undergo cataract extraction with intraocular lens (IOL) implantation, there is more variability in the postoperative refractions than for typical cataract patients.


The IOL calculations rely not on retinoscopy (objective refraction), but instead on keratometry (corneal curvature) and a-scan ultrasonography (axial length). One can only wonder if the diagnostic procedure of choice for these patients might someday be for the surgeon to remove the cataract, perform intraoperative retinoscopy of the aphakic eye, calculate the necessary lens power, then

place the desired IOL implant.


•In that way, the IOL would depend on the patient's refractive state rather than on artificial calculations based on the patient's altered ocular anatomy.

Degrees of Astigmatism

Mild Astigmatism

<1.00 diopters

Moderate Astigmatism

1.00 to 2.00 diopters

Severe Astigmatism

2.00 to 3.00 diopters

Extreme Astigmatism

>3.00 diopters

Clinical classification of astigmatism

1. Regular astigmatism :in which the two principle meridians are at right angle and is susceptible to easy correction by cylindrical lenses.

2. Oblique astigmatism :in which the two principle meridians are not at right angle but are crossed obiquely,it is corrected by using spherocylindrical lenses ,it is not very common.

3. Irregular astigmatism :where there are irregularities in the curvature of the meridians so that no geometrical figure is formed ,and the correction is very difficult.

Types of astigmatism

1.Simple astigmatism :where one of the foci falls upon the retina while the other focus may fall in front or behind the retina so that while one meridian is emmetropic the other meridian is either myopic or hypermetropic .


2.Compound astigmatism :where neither of the two foci lies upon the retina but both are placed in front of or behind the retina on the same direction ,the state of refraction is then entirely myopic (compound myopic astigmatism) or entirely hypermetropic (compound hypermetropic astigmatism) .


3.Mixed astigmatism :where one focus is in front of and the other is behind the retina, so that the refraction is myopic in one direction and hypermetropic in

the other.


Split focus in astigmatism

Other classification

Direct astigmatism :when the vertical curve is greater than the horizontal curve.

Indirect astigmatism :when the horizontal curve is greater than the

vertical curve.

B a c k

1.Patients with astigmatism have blurred or distorted vision at all distances.2. It can also cause images to appear doubled, particularly at night. 3.Patients have difficult focusing on various objects such as finely printed words and lines.4.Headache and fatigue of the eye are common as the person tends to strain his eyes. 5.Eye discomfort and irritation are also frequent.

What are the general symptoms of Astigmatism ?

Symptoms of low astigmatism (>1.0D) include

1. Asthenopia {tired eyes}, especially when doing precise دقيق work at a fixed distance.

2. Transient blurred vision relieved by rubbing the eyes "as in hyperopia" when doing precise work at a fixed distance.

3. Frontal headaches with long periods of visual concentration on a task.

Symptoms of high astigmatism (<1.0D) include

1. Blurred vision , asthenopia and frontal headache are more severe than in low astigmatism

2. Tilting of the head for oblique astigmatism3. Slinting to achieve "pinhole" vision clarity.4. Reading material held close to eyes to achieve

large (as in myopia) but blurred retinal image. 5. The letters in the book appear as running

together i.e. getting mixed up.

Optical condition in astigmatism

Causes of Astigmatism

Heriditary :• The exact cause remains unknown; however some

common types of astigmatism seem to run in families and may be inherited.

• It is thought that most people have some form of astigmatism as it is rare to find perfectly shaped curves in the cornea and lens, but the defect is rarely serious.

• The majority of these studies demonstrate an autosomal (of asexual chromosomes )dominant form of genetic transmission. Autosomal recessive transmission has been shown occasionally. Rarely, X-linked recessive form has also been reported.

Acquired causes of astigmatism1. Diseases of the cornea result in its deformity; an

extreme example is seen in conical cornea (keratoconus), while inflammations and ulceration of the cornea produce corneal scar.

2. Traumatic interference with the cornea may bring about the same result in this category we should include surgical trauma, particularly operations for cataract. Furthermore, corneal astigmatism can be induced by the pressure of swellings of the lids, whether the humble chalazion or a true neoplasm.

3. A transient deviation form normal can be produced by finger pressure on the eye, by contraction of the lids (blepharospasm ), or by the action of the extra-ocular muscles.

Acquired causes of astigmatism4. Curvature astigmatism of the lens also

occurs with great frequency. In great majority of cases such anomalies are small; but on occasion, as in lenticonus, they may be marked.

5. Not uncommonly the lens is placed slightly obliquely or out of line in the optical system and this, causing a certain amount of decentring, produces a corresponding astigmatism;

6. A traumatic subluxation of the lens has similar results

Keratoconus (KC)

Keratoconus is a progressive disorder in which the cornea assumes an irregular conical shape. The onset is at around puberty with slow progression thereafter. Though the ectasia may become stationary at any time, both eyes are affected, if only topographically, in almost all cases.

Keratoconus

Characteristics

INCIDENCE:Keratoconus is bilateral in approximately 96% of cases. Typically,

one eye is affected earlier, and the disease progresses further

than in the fellow eye. Keratoconus is often diagnosed in

persons in their early teens to early twenties .

There does not appear to be a significant difference in the

incidence of keratoconus between left and right eyes nor

between male and female subjects.

Histopathologic changes

It is still unclear what causes the corneal changes that occur in keratoconus. A triad of classic histopathologic changes has been observed:

1. Thinning of the corneal stroma.2. Breaks in bowman's layer.3. Iron deposition in the basal layers of the

corneal epithelium( Fleischer’s ring).

Etiology Of KC

1. Heredity

2. Eye rubbing and atopy

3. Contact lens wear

4. Abnormalities in ocular rigidity

and structure

Associations

Ocular associations include:1. vernal keratoconjunctivities,2. blue sclera,3. aniridia, 4. ectopia lentis, 5. Leber congenital amaurosis and6. retinitis pigmentosa.

predisposing factors

1. Rigid contact lens wear and 2. Constant eye rubbing have also

been proposed as predisposing factors.

By keratometry keratoconus is classified as mild (>48 D), moderate (48- 54D) and severe (<54D). Morphologically, the following are the three types:

1. Nipple حلمة cones, characterized by their small size (5mm) and steep curvature. The apical center is often either central or paracentral and displaced inferonasally

Classification and progressionClassification and progression

2. Oval cones or sagging . يرتخي which are , يتدلىlarger than the nipple form equals

5-6mm, ellipsoid ناقص م مجسand commonly displaced inferotemporally.

Classification and Classification and progression progression

3. Globus cones, which are the largest < 6mm and may involve over 75 % of the cornea.

Classification and Classification and progression progression

Clinical picture/ symptoms

1. Presentation is with impaired vision in one eye caused by progressive astigmatism and myopia.

2. The patient may report frequent changes in spectacle prescription or decreased tolerance to contact lens wear.

3. As a result of the asymmetrical nature of the condition, the fellow eye usually has normal vision with negligible astigmatism at presentation, which however, increases as the condition progresses.

1. Direct ophthalmoscopy

2. Retinoscopy

3. Slitlamp biomicroscopy

4. Keratometry

5. Placido disc

6. Corneal topography

7. Videokeratoscopy signs

Clinical picture/DIAGNOSIS

Often subtle, can be detected as follows:

1. Direct ophthalmoscopy from a distance of one foot shows an “oil droplet” reflex

2. Retinoscopy shows an irregular “scissor” reflex.

Clinical picture/ Early signs


Slitlamp biomicroscopy shows very fine, vertical, deep stromal striae ( vogt lines) which disappear with external pressure on the globe.

Prominent corneal nerves may also be present.


Keratometry shows irregular astigmatism where the principal meridians are no longer 90 degree apart and the mires cannot be superimposed.

Videokeratoscopy signs:

1. Compression of mires in affected region.

2. Color map showing increased power in isolated area of cone .

3. Inferior- superior dioptric asymmetry.


These devices are used to detect and quantify corneal surface curvature and the presence of astigmatism. A keratoscope uses light to project rings on the cornea. Observation through the keratoscope of the reflection of light from the cornea and inspection of the shape and spacing of the rings provide information about the degree of astigmatism.

Keratoscope and videokeratoscope

A keratoscope fitted with a video camera is called a videokeratoscope.

A videokeratoscope is the most common instrument used to quantify the change in corneal surface curvature, in a process called corneal topography.

Placido disk and keratoscope•Photokeratoscopy, which employ optical

principles that are similar to those of the keratometer, measure a larger surface area and provide a more complete

appreciation of corneal shape .

Placido disk and keratoscope

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Klein hand-held keratoscope and Placido disk


Videokeratography of with-the-rule, against-the

rule, oblique regular astigmatism


Corneal topography is the most sensitive method for detecting very early keratoconus.

Normal cornea

Keratoconus Suspect

Moderate Keratoconus

Advanced keratoconus

Large Inferior Cone Superior cone Small nipple cone

Clinical picture/ Late signs

• Late signs:1. Slit lamp shows: Progressive corneal thinning, to as little

as one – third of normal thickness, Marked increase of the depth of A C 2. Associated with poor visual acuity

resulting from marked irregular myopic astigmatism with steep keratometry (k) readings.

3. Bulging of the lower lid in down gaze (Munson’s sign)


4. Epithelial iron deposits (Fleischer’s ring) may surround the base of the cone and are visualized best with a cobalt blue filter of the slit lamp

5. Stromal scarring in severe cases.


6.Acute hydrops is an acute influx

of aqueous in to the cornea as a

result of a rupture in descemet

membrane. This causes a sudden

drop in visual acuity associated

with discomfort and watering.

Although the break usually heals

within 6-10 weeks and the corneal

oedema clears, avariable amount of

stromal scarring may develop.


Acute hydrops are initially

treated with hypertonic

saline and patching or a

soft bandage contact lens. Healing may result in

improved visual acuity as a result of scarring and flattening of the cornea. Keratoplasty should be deferred يرجئ . يؤجلuntil the oedema has resolved.

Differential diagnosis

1. Corneal Warpage ج Syndrome عو

2. High-riding rigid Gas-permeable lens 3. Keratoglobus

The topography of keratoconus: The topography of keratoconus: LECTURE 8LECTURE 8

The photokeratoscope or The photokeratoscope or placido placido discdisc can provide an overview of the can provide an overview of the cornea and can show the relative cornea and can show the relative steepness of any corneal area.steepness of any corneal area.

keratoconic corneakeratoconic cornea Normal corneaNormal cornea

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EyeSys System

The corneal surface has 75% of the refractive or light focusing ability of the eye. The EyeSys System utilizes placido disk technology to acquire images of the corneal surface. Placido disk technology is based on a technique that captures the reflection of rings of light off the surface of the cornea and measures the different distances between the ring

reflections . Current software technology captures the reflected

images with a digital camera, processes . يعاملthe data, and displays يعالج إبداء ; the إبانةinformation in multiple formats.

A Placido device is made up of many concentric light rings. The exact arrangement and number of rings may vary with different manufacturers

Light rings are projected on the cornea above.This image is captured and analyzed as thousands of computations are performed instantly.

corneal topography

مستكشف ; اف كش

• The map above was taken prior to simulated treatment. The horizontal red and orange areas are elevated above the cooler colors green blue areas demonstrating this patient’s against the rule astigmatism.

corneal topography• The same map is below after LASIK simulated laser

treatment. Observe the more uniform neutral green color centrally indicating a much smoother uniform surface without astigmatism (corrected with LASIK).

Photokeratoscopy view of early keratoconus

Note the pear-shaped الشكل pulling of كمثريthe central keratoscopy mires. The close

proximity of the rings (in the inferior-temporalportion of the eye(

indicates corneal steepening and greater distance between the rings

)in the superior-nasal portion of the eye(

indicates flattening.

corneal topography

• The typical spiral pattern of keratoconus progression. The condition commonly begins in the inferior-temporal quadrant, with the last area of the cornea to be topographically affected in the superior-nasal quadrant.

• In color-coded topographic images, red represents steeper corneal curvature, and the spectrum of yellow, green, and blue represents progressively flatter curvatures.

corneal topography

• The nipple-shaped form of keratoconus demonstrates a small central ectasis surrounded by 360 degrees of “normal” cornea.

corneal topographyThe most striking features of the nipple topography

are:• The often high degree of with-the-rule corneal

toricity confined to the central 5.0 mm of the cornea. • The nearly 360 degrees of “normal” mid-peripheral

cornea that surrounds the base of the cone. • The occasional presence of an elevated fibroplastic

nodule درنة at the apex of the cornea, hence the name nipple keratoconus. The superficial nodules are frequently eroded يحت . by the يتأكلpresence of a rigid contact lens, often necessitating: rigid gas permeable/soft contact lens (RGP/SCL) or piggyback designs,

corneal topography

Nipple-shaped keratoconus may also manifest as a small central ectasia with moderate to high with-the-rule corneal astigmatism in the form of regular bow tie.

corneal topography

Oval-shaped keratoconus is hallmarked by steepening of the inferior cornea

Globus-Shaped Topography

• The globus form of keratoconus affects the largest area of the cornea, often encompassing nearly three quarters(75%) of the corneal surface.

• Due to its size, nearly all of the keratoscopy rings will be encompassed مضمن ; مشمولwithin the area of the ectasia. Unlike the advanced forms of nipple or oval keratoconus, the globus cone has no island of “normal” mid-peripheral cornea above or below the midline.

Globus-Shaped Topography

Due to the size of the globus-shaped keratoconus, all nine rings of the photokeratoscopy image are encompassed by the conical area and no “islands” of normal mid-peripheral cornea are seen.

Normal corneal topographyFive qualitative patterns of normal corneal topography using a normalized scale. Top left, round; top center, oval; top right, symmetric bow-tie; bottom left, = asymmetric bow tie;

bottom center, irregular. In the normalized scale (bottom right) the range of dioptric power represented by each color varies among eyes, depending on the degree of corneal asphericity. Classification of normal corneal topography based on computer-assisted videokeratography.

Keratoconus topography• Videokeratographs mirror this distortion by

producing mires that are typically oval. The distance between rings is smallest at the steepest corneal slope and farthest apart superiorly where the cornea is flattest.

• Tangential curvature maps of projection-based systems provide additional information. On these maps the steepest slope is easily located as being inferior to the apex, producing an asymmetric bow tie الشكل فراشي رقبة This . رباطcorresponds to the exaggerated prolateمتطاول shape of the keratoconic eye.

• Projection-based systems can be used to locate the apex of the cone on elevation maps as the highest point.

Axial map• Axial map. Also called the "power" or

"sagittal" map, this output is the simplest of all the topographical displays. It shows variations in corneal curvature as projections

الشاشة على المتحركة الصور عرضand uses colors to represent dioptric values. Warm colors such as red and orange show steeper areas; cool colors such as blue and green denote the flatter areas.

Sometimes referred to as the instantaneous لحظى ،فورى ,local, or "true" map , توىit also displays the cornea as a topographical illustration, using colors to represent changes in dioptric value. However, the tangential strategy bases its calculations on a different mathematical approach that can more accurately determine the peripheral corneal configuration.

Tangential ي mapمماس

Tangential map• It does not assume the eye is spherical, and

does not have as many presumptionsفرض as the axial map regarding corneal shape.

• In fact it is the map that more closely represents the actual curvature of the cornea over the axial map. The tangential map recognizes sharp power transitions more easily than the axial map, and eliminates the "smoothing" appearance that appears on the axial map.

This utilizes yet another algorithm to give additional information about the cornea. An elevation map shows the measured height from which the corneal curvature varies (above or below) from a computer-generated reference surface. Warm colors depictيرسم . يصور. يصف points that are higher than the reference surface; cool colors designate lower points. This map is most useful in predicting fluorescein patterns with rigid lenses. Higher elevations (reds) represent potential areas of lens bearing, while the lower areas (greens) will likely show fluorescein pooling.

Elevation map.

Elevation map

Normal cornea

Keratoconus Suspect

Early Keratoconus

Progressive Nipple Keratoconus

Moderate Oval Keratoconus

Globus keratoconus

Advanced Globus keratoconus

corneal topography

•Corneal topography and imaging. Symmetric bow tie typical for regular

astigmatism .

http://www.emedicine.com/cgi-bin/foxweb.exe/makezoom@/em/makezoom?picture=%5Cwebsites%5Cemedicine%5Coph%5Cimages%5CLarge%5C371398P1010018.jpg&template=izoom2

corneal topography

•This elevation map shows inferior thinning in a patient's left eye .

Treatment Of keratoconus

Non-surgical

Surgical

SpectaclesContact lenses Penetratin

g Keratoplas

ty

Lamellar

Keratoplasty

Lamellarkeratoplasty

Intracorneal rings

Other Surgery

C3RC3R

Treatment that prevent Treatment that prevent progression of KCprogression of KC

Collagen cross linking treatments (C3R)Collagen cross linking treatments (C3R)

Recent treatment which is based on strengthen Recent treatment which is based on strengthen the cross-linking of corneal collagen by utilizes the cross-linking of corneal collagen by utilizes

riboflavin and ultraviolet (UV) light exposureriboflavin and ultraviolet (UV) light exposure . .

During the 30-minute riboflavin eyedrops are During the 30-minute riboflavin eyedrops are applied to the cornea, which are then activated applied to the cornea, which are then activated by a UV light. This is the process that has been by a UV light. This is the process that has been shown in laboratory and clinical studies to shown in laboratory and clinical studies to increase the amount of collagen cross-linking in increase the amount of collagen cross-linking in the cornea and strengthen the corneathe cornea and strengthen the cornea..

Collagen cross linking treatments causes the Collagen cross linking treatments causes the collagen fibers to thicken, stiffen, crosslink & collagen fibers to thicken, stiffen, crosslink & re-attach to each other, making the cornea re-attach to each other, making the cornea stronger and more stable thus convincingly stronger and more stable thus convincingly halting the progression of the disease. The halting the progression of the disease. The figures below demonstrate almost 10 diopters figures below demonstrate almost 10 diopters of corneal flattening in one patient before (left) of corneal flattening in one patient before (left) after this combined treatment (right)after this combined treatment (right)..

Advantages of Advantages of C3RC3R::

1.1. Simple one time treatmentSimple one time treatment2.2. No periodic treatments requiredNo periodic treatments required3.3. Halts the progress and causes some Halts the progress and causes some

regressionregression4.4. It is permanentIt is permanent5.5. No handling of lenses every dayNo handling of lenses every day6.6. Does not need any eye donationDoes not need any eye donation7.7. No precautionNo precaution8.8. No injectionNo injection9.9. No stitches as in keratoplastyNo stitches as in keratoplasty10.10. No incisions as in IntacsNo incisions as in Intacs11.11. Quick recovery, short follows upQuick recovery, short follows up

spectacle lensesspectacle lensesAs keratoconus progresses, As keratoconus progresses, spectacle lensesspectacle lenses often fail to often fail to provide adequate visual acuityprovide adequate visual acuity::

1.1. Especially Especially at night.at night. 2.2. This can be further complicated by the fact that the This can be further complicated by the fact that the

patient's glasses prescription may patient's glasses prescription may change frequentlychange frequently due due to the disease progress and can be limited by the degree to the disease progress and can be limited by the degree of of myopia and astigmatismmyopia and astigmatism that must be corrected. that must be corrected.

3.3. Also, keratoconus is often asymmetric therefore full Also, keratoconus is often asymmetric therefore full spectacle correction may be intolerable because of spectacle correction may be intolerable because of anisometropia and aniseikoniaanisometropia and aniseikonia. .

However, despite these limitations, spectacles can often However, despite these limitations, spectacles can often provide surprisingly good visual results in the provide surprisingly good visual results in the early stagesearly stages of the condition.of the condition.

contact lenses Contact lens options for keratoconusContact lens options for keratoconus

• When a keratoconic patient is no longer able to When a keratoconic patient is no longer able to obtain good visual acuity with spectacle lenses obtain good visual acuity with spectacle lenses because of increasing levels of irregular myopic because of increasing levels of irregular myopic astigmatism and higher-order aberrations, rigid astigmatism and higher-order aberrations, rigid contact lenses will be required, effectively to contact lenses will be required, effectively to provide a new anterior surface to the eye. provide a new anterior surface to the eye.

• Contact lenses are considered when vision is Contact lenses are considered when vision is not correctible to 6/9 by spectaclesnot correctible to 6/9 by spectacles and patients and patients become symptomatic.become symptomatic.

contact lensesThe successful fitting of contact lenses for The successful fitting of contact lenses for

keratoconus requires that three keratoconus requires that three objectivesobjectivesأهدافأهداف be met :be met :

1.1. The lens-to-cornea fitting relationship should The lens-to-cornea fitting relationship should create the least possible physicalcreate the least possible physical trauma trauma to the to the cornea. cornea.

2.2. The lens should provide The lens should provide stable visual acuitystable visual acuity throughout the patient's entire wearing throughout the patient's entire wearing schedule. schedule. جدولجدول

3.3. The lens should provide The lens should provide all day wearing comfort.all day wearing comfort.

Lens Designs for KeratoconusLens Designs for KeratoconusSoft lensesSoft lenses

Soft lenses have a limited role in correcting corneal Soft lenses have a limited role in correcting corneal irregularity, as they tend to drapeirregularity, as they tend to drape على على متدل over over متدلthe surface of the cornea and result in poor visual the surface of the cornea and result in poor visual acuity .acuity .

Hence, soft lenses are used only in the Hence, soft lenses are used only in the early early stages of the diseasestages of the disease. In such cases, the lenses . In such cases, the lenses are usually toric, and are fitted in the same are usually toric, and are fitted in the same manner, as they would be on a patient with manner, as they would be on a patient with myopic astigmatism. The fitting procedure begins myopic astigmatism. The fitting procedure begins by placing a soft lens with powers equal to the by placing a soft lens with powers equal to the manifest refraction vertexed manifest refraction vertexed القمة to the to theعلىplane of the cornea on the eye. Final lens power plane of the cornea on the eye. Final lens power is best calculated by performing a sphero-is best calculated by performing a sphero-cylinder refraction. cylinder refraction.

Toric soft contact lenses for early Toric soft contact lenses for early KCKC

soft contact lenses for early KCsoft contact lenses for early KC•However, some hydrogel lenses have been designed However, some hydrogel lenses have been designed

specially for keratoconus. specially for keratoconus. Hydrogel lenses are made relatively large in diameter, usually 13.5 to 14.5 mm in diameter which results in the lens edge being beyond the limbus on the sclera.

• They are designed to be thicker than regular soft lenses They are designed to be thicker than regular soft lenses so they retain a rigid shape to some extent. For this so they retain a rigid shape to some extent. For this reason they compress the central cornea and partially reason they compress the central cornea and partially trap a trap a tear pooltear pool, as with rigid corneal lenses. In effect, , as with rigid corneal lenses. In effect, they are rigid lenses made from hydrogel materials, and they are rigid lenses made from hydrogel materials, and they do appear to be giving a reasonable visual result they do appear to be giving a reasonable visual result

with some types of keratoconuswith some types of keratoconus . .

HYDROGEL (SOFT) LENSES• Hydrogel lenses increase the amount of

oxygen reaching the cornea as do most contact lenses. By making

the lenses thinner or increasing the water content, or both, more oxygen will reach

the cornea. It is not uncommon to have

hydrogel lenses made as thin as 0.035 mm.• Lenses are available up to about 75% water content with most lenses being used today range from 38% to 65% water .

Thick

Thin

soft contact lenses for early KCsoft contact lenses for early KC

Criteria to useCriteria to use::1.1. One criterion to use to determine if soft One criterion to use to determine if soft

lenses are acceptable is that they should lenses are acceptable is that they should induce no scarring. Often, soft contact induce no scarring. Often, soft contact lenses lead to repeated corneal lenses lead to repeated corneal abrasions, which can result in scarring.abrasions, which can result in scarring.

2.2. Another criterion is the patient must be Another criterion is the patient must be happy with his vision and is able to happy with his vision and is able to function properly in their daily activities.function properly in their daily activities.


Advantages Advantages 1) They afford higher levels of 1) They afford higher levels of comfortcomfort and and

longer wearing times, especially in longer wearing times, especially in patients intolerant to RGP corneal lenses patients intolerant to RGP corneal lenses or in monocular keratoconus.or in monocular keratoconus.

2) They are useful where the cone apex may 2) They are useful where the cone apex may be be displaceddisplaced, especially if it is very low., especially if it is very low.

3) They are relatively 3) They are relatively simple to fitsimple to fit. .


DisadvantagesDisadvantages1) Visual acuity may be variable (less corrected) in 1) Visual acuity may be variable (less corrected) in

cases of very high minus lenses.cases of very high minus lenses.2) Low-powered 2) Low-powered diagnosticdiagnostic lenses may not provide lenses may not provide

an accurate guide to the fit of the an accurate guide to the fit of the final lensfinal lens, , which may be extremely high powered.which may be extremely high powered.

3) If the condition (KC) has progressed, it may be 3) If the condition (KC) has progressed, it may be difficult to change to RGP lenses at a later difficult to change to RGP lenses at a later stage. stage.

Rigid gas permeable lensesRigid gas permeable lensesRigid gas permeable (RGP) corneal lenses are the Rigid gas permeable (RGP) corneal lenses are the lenses of first choice for correcting keratoconus. lenses of first choice for correcting keratoconus. They provide the best possible vision with the They provide the best possible vision with the maximum comfort so that the lenses can be worn maximum comfort so that the lenses can be worn

for a long period of timefor a long period of time . .The purpose of the lens is to cover the irregular The purpose of the lens is to cover the irregular astigmatism and the disordered anterior surface astigmatism and the disordered anterior surface optics of an ectatic cornea by providing a regular, optics of an ectatic cornea by providing a regular, spherical, optic surface before the eye (Figure spherical, optic surface before the eye (Figure below). The lens does not retard the progression below). The lens does not retard the progression

of the diseaseof the disease..

Rigid gas permeable lensesRigid gas permeable lenses

RGP contact lenses are primary RGP contact lenses are primary option for correcting KC visionoption for correcting KC vision

Keratoconic cornea

RGPlens

Piggyback Soft LensesPiggyback Soft Lenses• The technique of placing a rigid contact lens on top of a The technique of placing a rigid contact lens on top of a

soft lens (piggyback) was first described in the mid soft lens (piggyback) was first described in the mid 1970’s. Early piggyback systems consisted of thick, low 1970’s. Early piggyback systems consisted of thick, low Dk, soft lenses in combination with low Dk Dk, soft lenses in combination with low Dk silicone/acrylate rigid lenses. It was not surprising that silicone/acrylate rigid lenses. It was not surprising that this combination frequently resulted in corneal hypoxia this combination frequently resulted in corneal hypoxia and neovascularisation, which limited its usefulness. and neovascularisation, which limited its usefulness. However, with the recent introduction of high Dk silicone However, with the recent introduction of high Dk silicone hydrogel lenses and stable high Dk GP materials, the hydrogel lenses and stable high Dk GP materials, the dual lens system is now enjoying a rebirth, particularly dual lens system is now enjoying a rebirth, particularly for keratoconus patients experiencing comfort or lens for keratoconus patients experiencing comfort or lens position issueposition issue منفذ . منفذ . مخرج .. مخرج

Flexlens Piggyback lensFlexlens Piggyback lens

A recent piggyback lens system forA recent piggyback lens system for keratoconus keratoconus consisting of a high Dk soft lens and an RGP lens consisting of a high Dk soft lens and an RGP lens

combinationcombination..

A rigid lens riding piggyback over a soft lens.

Scleral lensesScleral lenses• Scleral lenses play a very significant role Scleral lenses play a very significant role

in cases of advanced keratoconus where in cases of advanced keratoconus where corneal lenses do not work and corneal corneal lenses do not work and corneal surgery is contra-indicated. Scleral surgery is contra-indicated. Scleral lenses completely neutralize any corneal lenses completely neutralize any corneal irregularity and can help patients irregularity and can help patients maintain a normal quality of life. These maintain a normal quality of life. These are large diameter lenses (23-25mm) are large diameter lenses (23-25mm) that rest on the sclera, and vaults over that rest on the sclera, and vaults over the cornea .the cornea .

A scleral and a corneal lens to A scleral and a corneal lens to compare the sizecompare the size..

Because of their size, they do Because of their size, they do not fall out; dust or dirt not fall out; dust or dirt particles cannot get behind particles cannot get behind them during wear. They are them during wear. They are surprisingly comfortable to surprisingly comfortable to wear because the edges of wear because the edges of the lens rests above and the lens rests above and below the eye lid margins so below the eye lid margins so there is no lens awareness. there is no lens awareness. The introduction of rigid gas The introduction of rigid gas permeable (RGP) materials permeable (RGP) materials has made this design more has made this design more readily availablereadily available..

Scleral lensesScleral lenses

AdvantagesAdvantages1.1. Comfortable to eyes.Comfortable to eyes.2.2. Any type of corneal irregularity is corrected.Any type of corneal irregularity is corrected.3.3. Easy to store.Easy to store.4.4. Long life.Long life.

DisadvantagesDisadvantages1.1. Much chair time is needed.Much chair time is needed.2.2. A very specialized fitting techniqueA very specialized fitting technique .

Rose K lensRose K lens•The Rose K lens is probably the most widely The Rose K lens is probably the most widely

fitted keratoconus lens worldwide and achieves fitted keratoconus lens worldwide and achieves an 85% first fit success in the UK. The Rose K an 85% first fit success in the UK. The Rose K lens design is a lens design is a fully flexible lensfully flexible lens that works well that works well on on early to advanced keratoconus patientsearly to advanced keratoconus patients . . Complex lens geometry, combined with the Complex lens geometry, combined with the enhanced material benefits makes the Rose K enhanced material benefits makes the Rose K lens the good fit enhancing patient comfort and lens the good fit enhancing patient comfort and visual acuity. Multiple parameters make fitting visual acuity. Multiple parameters make fitting the Rose K lens possible for most keratoconic the Rose K lens possible for most keratoconic eyes. The design starts with a standard 8.7mm eyes. The design starts with a standard 8.7mm diameter and works by decreasing the optic diameter and works by decreasing the optic zone diameter as the base curve gets steeperzone diameter as the base curve gets steeper..

Rose K™Rose K™ contact lens with small contact lens with small optic zoneoptic zone

The Rose K™ lensThe Rose K™ lens

Rose K lensRose K lens

Rose K lensRose K lens

Rose K™ contact lens with large optic zoneRose K™ contact lens with large optic zone

The Rose K™ lensThe Rose K™ lensAdvantagesAdvantages::1. Its complex geometry can be customized to suit 1. Its complex geometry can be customized to suit

each eye and can correct all of the myopia and each eye and can correct all of the myopia and astigmatism associated with keratoconus. astigmatism associated with keratoconus.

2. They are easy to insert, remove and clean .2. They are easy to insert, remove and clean .3. They provide excellent health to the eye, 3. They provide excellent health to the eye,

because they allow the cornea to "breath" because they allow the cornea to "breath" oxygenoxygen directly through the lens. directly through the lens.

4. Practitioners have the Rose K™ trial set fitting 4. Practitioners have the Rose K™ trial set fitting system which achieves a first fit system which achieves a first fit successsuccess in over in over 80% of patients' internationally80% of patients' internationally

surgical procedures

INTACS

Penetrating keratoplasty

Lamellar keratoplasty Epikeratophakia

Thermokeratoplasty

Treatment & Management Intrastromal Ring (Intacs®)Intrastromal Ring (Intacs®)• Definition: Intacs® were originally designed Definition: Intacs® were originally designed

and FDA approved in 1999 to correct mild and FDA approved in 1999 to correct mild nearsightedness (myopia). In patients with nearsightedness (myopia). In patients with keratoconus, Intacs® are indicated to reduce keratoconus, Intacs® are indicated to reduce myopia and astigmatism in those who are no myopia and astigmatism in those who are no longer able to achieve adequate vision with longer able to achieve adequate vision with contact lenses or glasses.contact lenses or glasses. Intacs are indicated Intacs are indicated for contact lens intolerant patients with for contact lens intolerant patients with keratoconus who have minimal central stromal keratoconus who have minimal central stromal scarring.scarring.

Intacs® are tiny (0.25mms thick) acrylic Intacs® are tiny (0.25mms thick) acrylic ring segmentsring segments

Intrastromal Ring (Intacs®)Intrastromal Ring (Intacs®)• They are an effective way to manage the They are an effective way to manage the

condition and restore functional acuity by condition and restore functional acuity by helping to restore the natural shape of a cornea helping to restore the natural shape of a cornea weakened by keratoconus. weakened by keratoconus.

• In a number of patients, Intacs® may delay or In a number of patients, Intacs® may delay or ultimately prevent the need for corneal ultimately prevent the need for corneal transplantation. A small incision is made in the transplantation. A small incision is made in the periphery of the cornea and two thin arcs of periphery of the cornea and two thin arcs of polymethyl methacrylate slid slid ينزلقينزلق between between the layers of the corneal the layers of the corneal stroma, the incision , the incision then being closed. then being closed.

• The segments push out against the curvature of The segments push out against the curvature of the cornea, flattening the peak of the cone and the cornea, flattening the peak of the cone and returning it to a more natural shape. returning it to a more natural shape.

http://en.wikipedia.org/wiki/Polymethyl_methacrylate

http://en.wikipedia.org/wiki/Stroma

The procedure, carried out on an outpatient basis under The procedure, carried out on an outpatient basis under local anesthesia, offers the benefit of being reversible and even , offers the benefit of being reversible and even

potentially exchangeable as it involves no removal of eye tissuepotentially exchangeable as it involves no removal of eye tissue

http://en.wikipedia.org/wiki/Local_anaesthesia

Intrastromal Ring (Intacs®)Intrastromal Ring (Intacs®)• The inserts are designed to be placed at a depth of The inserts are designed to be placed at a depth of

approximately two-thirds the corneal thickness and approximately two-thirds the corneal thickness and are surgically inserted through a small radial incision are surgically inserted through a small radial incision into a troughinto a trough مجرى . مجرى . قناة created within the corneal created within the corneal قناةstroma. The inserts shorten the corneal arc length stroma. The inserts shorten the corneal arc length and have a net effect of flattening the central cornea.and have a net effect of flattening the central cornea.

• The amount of flattening is determined by the The amount of flattening is determined by the insert's thickness. Rings are available in thicknesses insert's thickness. Rings are available in thicknesses of 0.25, 0.275, 0.3, 0.325 and 0.35 mm and are of 0.25, 0.275, 0.3, 0.325 and 0.35 mm and are oriented horizontally in the cornea at 3 and 9 o'clock. oriented horizontally in the cornea at 3 and 9 o'clock.

Intacs® - Clinical FactsIntacs® - Clinical Facts

• Clinical studies on the effectiveness of Clinical studies on the effectiveness of intrastromal rings on keratoconus are in their intrastromal rings on keratoconus are in their early stages, and results have so far been early stages, and results have so far been generally encouraging, though they have yet to generally encouraging, though they have yet to enter into wide acceptance with all refractive enter into wide acceptance with all refractive surgeons. surgeons.

• In comparison with a penetrating keratoplasty, In comparison with a penetrating keratoplasty, the requirement for some vision correction in the the requirement for some vision correction in the form of hydrophilic (soft) contact lenses or form of hydrophilic (soft) contact lenses or spectacles may remain subsequent to the spectacles may remain subsequent to the Intacs® Intacs® operation.operation.


Potential complications of intrastromal rings Potential complications of intrastromal rings include :include :

1.1. accidental penetration through to the accidental penetration through to the anterior chamber when forming the anterior chamber when forming the channel.channel.

2.2. post-operative post-operative infection of the cornea. of the cornea. 3.3. migration or extrusion of the segments. migration or extrusion of the segments.

http://en.wikipedia.org/wiki/Infection


• Thousands of keratoconus eyes have been Thousands of keratoconus eyes have been treated successfully with Intacs®. Most treated successfully with Intacs®. Most patients have experienced better quality of life, patients have experienced better quality of life, improved visual quality and stabilization of the improved visual quality and stabilization of the keratoconic condition. The rings offer a good keratoconic condition. The rings offer a good chance of vision improvement even in chance of vision improvement even in otherwise hard to manage eyes, but it is not otherwise hard to manage eyes, but it is not guaranteed and in a few cases may worsen.guaranteed and in a few cases may worsen.

• Considerable research has been collected on Considerable research has been collected on patients having undergone the surgery since patients having undergone the surgery since 1997 as demonstrated by the following results:1997 as demonstrated by the following results:

Intrastromal Ring (Intacs®)Intrastromal Ring (Intacs®)IMPROVED VISION :IMPROVED VISION :• 71% gained 71% gained 1 or more lines1 or more lines of Best Corrected of Best Corrected

Visual Acuity. Visual Acuity. • 73% gained 73% gained 2 or more lines2 or more lines in Uncorrected in Uncorrected

Visual Acuity. Visual Acuity. • Eyes with worse preoperative acuity had Eyes with worse preoperative acuity had

greater improvements in greater improvements in postoperativepostoperative acuity. acuity. • Eyes with Eyes with corneal scarringcorneal scarring also showed some also showed some

improvementimprovement


SAFETY:SAFETY:• Intacs® for keratoconus mirror the safety of FDA-Intacs® for keratoconus mirror the safety of FDA-

approved Intacs® for Myopia. approved Intacs® for Myopia. • If required, Intacs® can be removed preserving the If required, Intacs® can be removed preserving the

option for corneal transplantation. option for corneal transplantation. STABILIZED VISION:STABILIZED VISION:• Intacs® may restore functional vision by allowing Intacs® may restore functional vision by allowing

the eye to be effectively corrected with contact the eye to be effectively corrected with contact lenses or glasses besides intacs if needed.lenses or glasses besides intacs if needed.

• Intacs® flatten and shift the cone centrally, Intacs® flatten and shift the cone centrally, restructuring the corneal architecture to a normal restructuring the corneal architecture to a normal prolate shape.prolate shape.

• Intacs® add structural integrity Intacs® add structural integrity سالمةسالمة to the to the cornea without invading the opticalcornea without invading the optical zonezone .

Corneal topography before and after Corneal topography before and after Intacs® insertionIntacs® insertion

Penetrating KeratoplastyPenetrating KeratoplastyLecture 10Lecture 10

Since the 1950’s, penetrating keratoplasty has Since the 1950’s, penetrating keratoplasty has been the primary surgical procedure for been the primary surgical procedure for treatment of keratoconus. A corneal treatment of keratoconus. A corneal transplant,transplant, also known as a also known as a corneal graftcorneal graft, or , or as a as a penetrating keratoplastypenetrating keratoplasty, involves the , involves the removal of the central portion (called a removal of the central portion (called a button) of the diseased cornea and replacing button) of the diseased cornea and replacing it with a matched donor button of cornea.it with a matched donor button of cornea.

Penetrating keratoplasty for Penetrating keratoplasty for treatment of keratoconustreatment of keratoconus..

Donated button

Patient’s corneal rim

penetrating keratoplastypenetrating keratoplastyIndicationsIndications

The primary indications for penetrating keratoplasty in patients The primary indications for penetrating keratoplasty in patients with keratoconus are :with keratoconus are :

1.1. contact lens intolerance,contact lens intolerance,2.2. progression of cone toward the corneal limbus,progression of cone toward the corneal limbus,3.3. in severe cases, threatened corneal perforationin severe cases, threatened corneal perforation. . 4.4. Uncomplicated corneal hydrops.Uncomplicated corneal hydrops.5.5. If the contact lenses fail to provide adequate visual If the contact lenses fail to provide adequate visual

acuity due to corneal scarring. acuity due to corneal scarring. 6.6. Sharp bilateral visual acuity is required for Sharp bilateral visual acuity is required for

recreational recreational استجمامياستجمامي or professional requirements.or professional requirements.

Penetrating Keratoplasty Surgical techniques Penetrating Keratoplasty Surgical techniques

The figures from below illustrate the procedureThe figures from below illustrate the procedure

This technique is suitable when disease A circular cut is made into This technique is suitable when disease A circular cut is made into through the full thickness of the cornea. the diseased corneathrough the full thickness of the cornea. the diseased cornea

Penetrating KeratoplastyPenetrating Keratoplasty

The diseased cornea isThe diseased cornea is removedremoved

A A healthy cornea ishealthy cornea is transplantedtransplanted

The cornea transplant is held inThe cornea transplant is held in place with ultra-fine sutures. These place with ultra-fine sutures. These are not visible to the naked eye. The transplant bonds slowly to the are not visible to the naked eye. The transplant bonds slowly to the

patient’s cornea and the sutures are then removedpatient’s cornea and the sutures are then removed..

Penetrating KeratoplastyPenetrating KeratoplastyPost operative carePost operative care

• The healing process following transplant is long, The healing process following transplant is long, often taking a year or longer. The time from often taking a year or longer. The time from surgery to the removal of the stitches is surgery to the removal of the stitches is commonly 6 to 17 months.commonly 6 to 17 months.

• The patient may be on steroid drops for months.The patient may be on steroid drops for months.• Initially following surgery the donor button is Initially following surgery the donor button is

swollen and even following healing the button is swollen and even following healing the button is usually thicker than the corneal bed in which it usually thicker than the corneal bed in which it rests. A thick white ring of scarring between the rests. A thick white ring of scarring between the donated button and the patient's outer cornea is donated button and the patient's outer cornea is performed. performed.

• The white radial marks are where stitches were The white radial marks are where stitches were placed to hold the transplant in position.placed to hold the transplant in position.


Graft rejection reactions occur in 11% to 18% of Graft rejection reactions occur in 11% to 18% of the patients. Signs of graft rejection include:the patients. Signs of graft rejection include:

1.1. ciliary's flush. ciliary's flush. 2.2. anterior chamber flare. anterior chamber flare. 3.3. keratic precipitates.keratic precipitates.4.4. KhodaoustKhodaoust line and Krachmer's spots. Signs line and Krachmer's spots. Signs

of graft rejection are reported to occur from 1 of graft rejection are reported to occur from 1 month to 5 years following surgery. The month to 5 years following surgery. The rejection rate for bilateral grafts is higher than if rejection rate for bilateral grafts is higher than if only only one eye is graftedone eye is grafted. In the . In the bilateral bilateral casescases, when a rejection reaction occurs it is , when a rejection reaction occurs it is commonly in both eyes. commonly in both eyes.

Uveitis

Keratic precipitates


• If the second eye is to be grafted, there is If the second eye is to be grafted, there is usually a period of at least one year between usually a period of at least one year between grafts. If signs of rejection occur, aggressive grafts. If signs of rejection occur, aggressive treatment with steroids is begun. treatment with steroids is begun.

• Usually the reaction is overcome and the graft Usually the reaction is overcome and the graft remains clear. Over 90% of the corneal grafts remains clear. Over 90% of the corneal grafts are successful with some studies reporting are successful with some studies reporting 97% to 99% success rates at 5 and 10 years.97% to 99% success rates at 5 and 10 years.


• Large amounts of astigmatism are common Large amounts of astigmatism are common following keratoplasty. One study found an following keratoplasty. One study found an average of 5.56 DC with a range from 0 to 17 D average of 5.56 DC with a range from 0 to 17 D following suture removal, with other studies following suture removal, with other studies showing an average of 5.4 DC .showing an average of 5.4 DC .

• The patient's spectacle prescription may The patient's spectacle prescription may fluctuate for some months following surgery. fluctuate for some months following surgery. Refractive changes and keratometry or corneal Refractive changes and keratometry or corneal topography can be used to follow the healing topography can be used to follow the healing processprocess .

Complications of keratoplastyComplications of keratoplasty

Surgery of keratoplasty involves Surgery of keratoplasty involves risksrisks that include:- that include:-1.1. High post-operative regular and/or irregular High post-operative regular and/or irregular

astigmatism. myopia and astigmatism may astigmatism. myopia and astigmatism may reduce vision directly or from aniseikonia.reduce vision directly or from aniseikonia.

2.2. Graft rejection.Graft rejection.3.3. Infection inside the eye (endophthalmitis). Infection inside the eye (endophthalmitis). 4.4. Glaucoma.Glaucoma.5.5. Steep or flat grafts.Steep or flat grafts.6. Recurrence of KC in the new graft.

Lamellar KeratoplastyLamellar KeratoplastyLecture 11Lecture 11

1.1. Recently a major step forward in cornea Recently a major step forward in cornea transplantation for keratoconus has transplantation for keratoconus has occurred. This is the advent occurred. This is the advent ; قدوم قدوم ; مجيء of of مجيءa form of partial corneal transplantation a form of partial corneal transplantation called deep anterior lamellar keratoplasty. called deep anterior lamellar keratoplasty.

2.2. In this technique a circular disc of diseased In this technique a circular disc of diseased tissue from the centre of the patient’s own tissue from the centre of the patient’s own cornea is cornea is removedremoved, but the innermost layer , but the innermost layer (endothelium ) of the patient’s cornea is left (endothelium ) of the patient’s cornea is left behind. behind.

3.3. The transplanted donor cornea has its own The transplanted donor cornea has its own endothelium removed before it is sutured in endothelium removed before it is sutured in place.place.

Lamellar KeratoplastyLamellar Keratoplasty• This technique is appropriate in keratoconus This technique is appropriate in keratoconus

because in this disease the stroma is abnormal because in this disease the stroma is abnormal whilst the endothelium is healthy. whilst the endothelium is healthy.

• Preserving the patient’s healthy endothelium has Preserving the patient’s healthy endothelium has major advantages because in this form of cornea major advantages because in this form of cornea transplantation transplantation rejection of the transplant almost rejection of the transplant almost never occurs.never occurs.

• Always perform partial or deep anterior lamellar Always perform partial or deep anterior lamellar keratoplasty in keratoconus when it is possible keratoplasty in keratoconus when it is possible to do so. to do so.

• However if the keratoconus is too advanced, for However if the keratoconus is too advanced, for example the cornea is example the cornea is severely scarred, this severely scarred, this surgery may not be possiblesurgery may not be possible and penetrating and penetrating keratoplasty will be done insteadkeratoplasty will be done instead .

Lamellar KeratoplastyLamellar Keratoplasty Diseased corneas may be scarred and/or abnormally Diseased corneas may be scarred and/or abnormally

shaped.shaped.

Air is injected into the cornea to separate the Air is injected into the cornea to separate the

abnormal front region from endothelialabnormal front region from endothelial back regionback region

The surgeon will remove the diseased stromal region The surgeon will remove the diseased stromal region

retaining the endotheliumretaining the endothelium

the diseased stromal regionthe diseased stromal regionIs removedIs removed

TheThe abnormal stroma is then completely removedabnormal stroma is then completely removed

A healthy donated cornea is transplanted into the A healthy donated cornea is transplanted into the patient’s cornea to replace the diseased front region. patient’s cornea to replace the diseased front region. The corneal transplant consists only of the front region The corneal transplant consists only of the front region of healthy cornea – the endothelial back region has of healthy cornea – the endothelial back region has been removed- so that the new cornea fits exactly into been removed- so that the new cornea fits exactly into

the patient’s endotheliumthe patient’s endothelium.

Unremoved endothelium

The cornea transplant is secured with ultra-fine suturesThe cornea transplant is secured with ultra-fine sutures 11/0

ultra-fine sutureultra-fine suture

LASIK in KeratoconusLASIK in Keratoconus

• Keratoconus is generally considered to be Keratoconus is generally considered to be a contraindication for Lasik, PRK, LASEK, a contraindication for Lasik, PRK, LASEK, or any other refractive surgery technique or any other refractive surgery technique that removes tissue. that removes tissue.

• There is a possibility that these There is a possibility that these procedures could further weaken a cornea procedures could further weaken a cornea that is affected by keratoconus resulting in that is affected by keratoconus resulting in a further unstable cornea , liable to future a further unstable cornea , liable to future perforation.perforation.

• Epikeratoplasty is effective in patients intolerant to contact lenses without significant central corneal scarring. In this procedure a preshaped button of donor stromal tissue called a lenticule is placed on the deepithelialized anterior surface of the recipient cornea.

Epikeratoplasty (Epikeratophakia)

Epikertophakia

The unoperated eye The operated eye

Prevalenceسيادة of Refractive Errors

Factors that affect the prevalence of refractive errors :-

About refractive error distribution for example Daniel Etyale of the W.H.O. reported at a special session on refractive error at an International Agency for Prevention of Blindness meeting in 2001, that 5 -15 percent of children are considered to have refractive errors, the majority of which are uncorrected (neglected).

I-Gender : Some studies found higher prevalence of myopia among females than among males.

Prevalence of Refractive Errors

II-Race :1. Prevalence of myopia is higher among

Americans of European ancestry سلسلة . than among African Americans النسب

2. Very high prevalence of myopia have been, reported among Asians.

Prevalence of Refractive ErrorsIII-Occupation :1. Myopia is more common in persons who have

occupations involving near work. 2. Hyperopia has often been found to be

associated with poor reading ability.

Screening of Refractive ErrorsIV-Family history :Myopia is more common among persons with

a family history of myopia. Familial resemblance is probably due in part to inheritance and in part to common life style factors.

Screening of Refractive Errors

• Recent studies about refractive error distribution :Data from 29,281 people in the US, western Europe and Australia below 12 years of age showed a prevalence for hyperopia (plus 3D or greater) of 9.9 percent, 11.6 percent, and 5.8 percent, respectively, and for myopia (minus 1D or more) 25.4 percent, 26.6 percent, and 16.4 percent for these population samples.

Correction of refractive errors

General guidelines for treatment of General guidelines for treatment of hypermetropiahypermetropia

Optical correction Spectacles :

– In young children below the age of 6 or 7, some degree of hypermetropia is physiological, and a correction needs to be given only if the error is high or if strabismus is present .

– In those between 6 and 16 years, especially when they are working strenuously at school, smaller errors may require correction .

– If a suspicion of eye strain is suggested by more indefinite signs, a complaint of headache or unaccountable lassitude ; إرهاق in all إجهادthese cases the refraction should be conducted under a cycloplegic eye drops.

Correction of refractive errors Hyperopia

Unless there is esodeviation or evidence of reduced vision , it is not necessary to correct hyperopia .

• When hyperopia and esotropia coexist , initial management includes full correction of the refractive error after cycloplegia .

• When there is spasm of the accommodation we correct the whole of the error .

• In a school – age child , the full refractive correction may cause blurring of distance vision because of the inability to relax accommodation fully ,thus we deduce about one diopter of the objective full cycloplegic refraction for better distant vision.

Hypermetropia " HM" Generally , the more fully the error is corrected ,

the better the result , always provided that the lenses are compatible with good vision.

As a compromise in a difficult case like high HM , it may be well to under correct considerably at first ,and to strengthen the lenses at intervals gradually of a few months until the full correction is comfortably borne , Or it may help to advise weaker lenses to correct for distance and the full correction

for close work.

Hypermetropia " HM" Finally the symptoms of accommodative asthenopia may indicate a general constitutional state as a part of general

body strain. Its Rx is to be adequate , should not be confined to the correction of the optical apparatus alone , but should include an inquiry into the general physical and nervous state , and if necessary , should involve a reorganization of the habits and activities of the individual so that he lives within the limits of his

capabilities.

Predisposing factors for asthenopia

Thus typical symptoms of asthenopia come on in-:1. The child starting school .2. In the young studying for an examination . 3. In the girl leaving the comparative ease of

home life and setting out in business .4. In the adult in periods of over work and

anxiety ,5. And in them all in states of physical debility ( systemic diseases) and mental depression .

Surgery for high HM

a- Thermokeratoplasty , in which corneal curvature is by appropriately sited burns , produces such variable effects as to vitiate يفسدits widespread acceptability at present

b- The use of Excimer laser and holmium lasers surgery Laser in-situ keratomileusis (LASIK) is now well known to correct up to 5 D of HM.

Treatment of myopiaGeneral guidelines for TreatmentGeneral guidelines for Treatment::

The goals for managementThe goals for management of the patient with myopia are: of the patient with myopia are:1.1. Clear, comfortable, efficient binocular vision Clear, comfortable, efficient binocular vision 2.2. Good ocularGood ocular healthhealth..• The primary symptom in patients with low and The primary symptom in patients with low and

moderate myopia is moderate myopia is lack of clear vision at distancelack of clear vision at distance, , which can be restored by optical correction. which can be restored by optical correction.

• Treatment directed to slow the progression of myopia Treatment directed to slow the progression of myopia is referred to as "myopia control". Effective myopia is referred to as "myopia control". Effective myopia control results in less severe myopia and less control results in less severe myopia and less vitreous chamber elongation than would otherwise vitreous chamber elongation than would otherwise have occurred.have occurred.

Treatment of myopia• Regimens to reduce myopia lessen dependence Regimens to reduce myopia lessen dependence

on spectacles or contact lenses, but they do not on spectacles or contact lenses, but they do not lessen the risk for myopic sequelae. lessen the risk for myopic sequelae.

• ChildrenChildren should be fully corrected and, if under should be fully corrected and, if under 8 years of age, instructed to wear their glasses 8 years of age, instructed to wear their glasses constantlyconstantly both to avoid developing the habit of both to avoid developing the habit of squinting (Slinting)squinting (Slinting) and to enhance developing a and to enhance developing a normal accommodation-convergence normal accommodation-convergence reflex.reflex.

• If the refractive error is low, the child may wear If the refractive error is low, the child may wear the glasses the glasses intermittently intermittently as needed, e.g., at as needed, e.g., at schoolschool .

Treatment of myopia

• Undercorrection of myopia Undercorrection of myopia in early childhood in early childhood may result in an adult who has never developed may result in an adult who has never developed a normal amount of accommodation for near a normal amount of accommodation for near focus. This person will be uncomfortable in full focus. This person will be uncomfortable in full correction and complain that the glasses are too correction and complain that the glasses are too strong and "pull" his or her eyes.strong and "pull" his or her eyes.

• Cycloplegic refractionsCycloplegic refractions are mandatory. All are mandatory. All strabismic children need cycloplegia, especially strabismic children need cycloplegia, especially esotropic children and very high myopes (> 10 esotropic children and very high myopes (> 10 D), atropine refraction may be necessary.D), atropine refraction may be necessary.

Treatment of myopia

• In generalIn general, the refractive error, including , the refractive error, including cylinder, should be fully corrected. Young cylinder, should be fully corrected. Young children tolerate cylinder well. children tolerate cylinder well.

• Intentional undercorrection of a myopic Intentional undercorrection of a myopic esotropeesotrope to decrease the angle of to decrease the angle of deviation is rarely tolerated. deviation is rarely tolerated.

• Intentional overcorrectionIntentional overcorrection of a myopic of a myopic refractive error may be of some value in refractive error may be of some value in controlling an intermittent exodeviation.controlling an intermittent exodeviation.

Treatment of myopia

• ParentsParents should be educated about the natural should be educated about the natural progression of myopia and the need for frequent progression of myopia and the need for frequent refractions and possible prescription changes.refractions and possible prescription changes.

• Contact lensesContact lenses may be a desirable option in may be a desirable option in older children to avoid the problem of image older children to avoid the problem of image minification found with high- minus lenses. minification found with high- minus lenses.

• AutorefractometerAutorefractometer may be used to refract may be used to refract myopic patients, but prescribing directly from the myopic patients, but prescribing directly from the findings can be hazardous.findings can be hazardous.

Available Treatment Options for Available Treatment Options for myopiamyopia Lecture 12

Optical correctionOptical correction :in the form of spectacles or contact :in the form of spectacles or contact lenses provides clear distance vision. Whether lenses provides clear distance vision. Whether spectacles or contact lenses are preferable in a spectacles or contact lenses are preferable in a given case depends upon numerous factors, given case depends upon numerous factors, including:including:

1.1. patient's agepatient's age, , 2.2. motivation motivation حفز ، حفز تشويق ، ,for wearing contact lenses,for wearing contact lenses تشويق3.3. compliance compliance ; انقياد انقياد ; انصياع with contact lens care with contact lens care انصياع

procedures,procedures,4.4. corneal physiologycorneal physiology, , 5.5. and and financial financial considerations.considerations.

Treatment of myopia•Spectacle:Spectacle: (Spherical (Spherical concaveconcave lenses) lenses)

•

FOCUS FOCUS

Treatment of myopia11) Below 6 D (I.e. for low and moderate myopia). ) Below 6 D (I.e. for low and moderate myopia).

Full correction must be ordered. Children should Full correction must be ordered. Children should wear their distant vision glasses wear their distant vision glasses constantlyconstantly for for two reasons:two reasons:

aa) Visual development: If the glasses are not worn, ) Visual development: If the glasses are not worn, the image is not formed on the retina. It is no the image is not formed on the retina. It is no longer stimulated and the eye becomes 'lazy' longer stimulated and the eye becomes 'lazy' (amblyopic).(amblyopic).

b)b) Mental development - without glasses myopes Mental development - without glasses myopes do not take interest in school since they cannot do not take interest in school since they cannot see the blackboard, also they can not form a see the blackboard, also they can not form a good idea about the nature or the real shape good idea about the nature or the real shape and size of objects.and size of objects.

Treatment of myopia

2)2) Above 6 D (high myopia) - slight under Above 6 D (high myopia) - slight under correction, because strong minus lenses correction, because strong minus lenses considerably diminish the size (minify) of considerably diminish the size (minify) of the retinal images and make them very the retinal images and make them very bright and clear. The very bright and clear bright and clear. The very bright and clear images are uncomfortable to the myope images are uncomfortable to the myope because the retina has been accustomed because the retina has been accustomed to large and indistinct images.to large and indistinct images.

Treatment of myopia

Contact lenses are indicated Contact lenses are indicated particularly in high myopia.particularly in high myopia.

•

Advantages and disadvantages of contact lenses

Advantages:1. Contact lenses may have optical advantages for some patients in

addition to the cosmetic benefit and the convenience مالءمة of not having to wear glasses.

2. In high degrees of ametropia, peripheral distortions are reduced with contact lenses due to their small diameter and thinness.

3. Even binocular aphakics enjoy the better peripheral vision, minimum distortion, and reduced magnification that they get with contact lenses.

4. A patient with keratoconus or an irregular cornea for some other reason can frequently achieve satisfactory vision with contact lenses when little or no improvement can be obtained with spectacle.

5. The advantages for those engaged in athletics or with special occupational needs are obvious.

Disadvantages:

1. Contact lenses are expensive and easily lost or destroyed. 2. Rigid lenses are initially uncomfortable and require a period

of adaptation.3. With the exception of extended-wear lenses, which are

replaced at prescribed intervals, the care and cleaning of daily-wear contact lenses are important and must be done on a daily basis.

4. Wearing time may be limited by physiologic factors, and the patient may still have to wear glasses part of the time.

5. A superficial ocular infection becomes more significant in the contact lens patient.

6. Corneal ulcers may occur with contact lenses; they never occur as a result of wearing spectacles.

7. Foreign bodies may become entrapped under a contact lens instead of being immediately washed out by tears.

Treatment of myopia

• Advantages of contact lens over spectacles :Advantages of contact lens over spectacles :1)1) Provide normal field of vision. Provide normal field of vision.2)2) Aberrations associated with spectacles – Aberrations associated with spectacles –

prismatic distortion, spherical and chromatic prismatic distortion, spherical and chromatic aberration are eliminated.aberration are eliminated.

3)3) Cosmetically contact lenses are more pleasant Cosmetically contact lenses are more pleasant than thick myopic glasses. However contrary to than thick myopic glasses. However contrary to popular belief contact lenses have not been popular belief contact lenses have not been proved to reduce the degree of myopia. proved to reduce the degree of myopia.

Treatment of myopiaOrthokeratologyOrthokeratology• Orthokeratology is the programmed fitting of a Orthokeratology is the programmed fitting of a

series of contact lenses, over a period of weeks series of contact lenses, over a period of weeks or months, to flatten the cornea and reduce or months, to flatten the cornea and reduce myopia. Studies of orthokeratology with standard myopia. Studies of orthokeratology with standard rigid contact lenses show that individual’s rigid contact lenses show that individual’s response varies considerably to orthokeratology, response varies considerably to orthokeratology, with myopia reduction up to 3.00 D obtained in with myopia reduction up to 3.00 D obtained in some patients. some patients.

• The average reduction reported in studies was The average reduction reported in studies was 0.75-1.00 D; most of this reduction occurs within 0.75-1.00 D; most of this reduction occurs within the first 4-6 months of the orthokeratology the first 4-6 months of the orthokeratology program. program.

Treatment of myopia

• Corneas with greater peripheral flattening Corneas with greater peripheral flattening are thought more likely to have successful are thought more likely to have successful central flattening, thus leading to reduced central flattening, thus leading to reduced myopia via orthokeratology.myopia via orthokeratology.

• With adequate follow up care, With adequate follow up care, orthokeratology is a safe and effective orthokeratology is a safe and effective procedure. However, studies suggest that procedure. However, studies suggest that refractive error shifts toward the original refractive error shifts toward the original baseline( starting linebaseline( starting line ) in patients.n patients.

Treatment of myopia

Visual hygiene Visual hygiene recommendationsrecommendations include include the following:the following:

1.1. When reading or doing intensive near When reading or doing intensive near work, take a break about every 30 work, take a break about every 30 minutes. During the break, stand up and minutes. During the break, stand up and look out a window.look out a window.

2.2. When reading, maintain proper distance When reading, maintain proper distance from the book .The book should be at from the book .The book should be at least as far from the eyes as 40 cm.least as far from the eyes as 40 cm.

Treatment of myopia

3.3. Be sure that illumination is sufficient for Be sure that illumination is sufficient for reading. Avoid glare on the page by using a reading. Avoid glare on the page by using a diffuse light source and allowing it to shine on diffuse light source and allowing it to shine on the page from behind (over the the page from behind (over the shoulder) ,rather than shining or reflecting shoulder) ,rather than shining or reflecting toward the eyes.toward the eyes.

4.4. Read or do other visual work using a relaxed Read or do other visual work using a relaxed upright posture.upright posture.

5.5. Place a limit on the time spent watching Place a limit on the time spent watching television and watching video games. Sit 5-6 television and watching video games. Sit 5-6 feet away from the television.feet away from the television.

Treatment of myopia

• LasikLasik (laser Assisted in situ (laser Assisted in situ keratomileusiskeratomileusis): In LASIK a thin, central flap is ): In LASIK a thin, central flap is created in the outer layers of the cornea, created in the outer layers of the cornea, consisting of the epithelium and a portion of the consisting of the epithelium and a portion of the outer stroma. Following lifting of the flap, the outer stroma. Following lifting of the flap, the laser is used to reshape the exposed stromal laser is used to reshape the exposed stromal bed. The flap is replaced without the need for bed. The flap is replaced without the need for sutures, and the edges heal over night.sutures, and the edges heal over night.

• The entire process takes just minutes to The entire process takes just minutes to perform. As the flap of the epithelium remains perform. As the flap of the epithelium remains intact immediately following the procedure, intact immediately following the procedure, vision recovers quickly and discomfort is kept to vision recovers quickly and discomfort is kept to a minimum. a minimum.

General guidelines for final General guidelines for final correction of astigmatismcorrection of astigmatism

1.1. In children requiring correction, the full In children requiring correction, the full astigmatic correction is given.astigmatic correction is given.

2.2. If the child is amblyopic from unilateral If the child is amblyopic from unilateral astigmatism; a trial of lenses is indicated before astigmatism; a trial of lenses is indicated before occlusion therapy. occlusion therapy.

3.3. In adult who is asymptomatic, be waryIn adult who is asymptomatic, be wary . حذر . حذر of changing the axis of their correcting of changing the axis of their correcting محترسمحترسcylinder even if apparently incorrect, they have cylinder even if apparently incorrect, they have achieved adaptation to distortion and blur and achieved adaptation to distortion and blur and will often be unhappy with any change.will often be unhappy with any change.


4.4. If an adult was previously fully corrected and If an adult was previously fully corrected and the amount of astigmatism has changed, he the amount of astigmatism has changed, he will probably tolerate full correction, especially will probably tolerate full correction, especially if the axis at 90 or 180.if the axis at 90 or 180.

5.5. If an adult was not corrected for the full If an adult was not corrected for the full amount of astigmatism, distortion may result in amount of astigmatism, distortion may result in a real problem. The only way to predict this is a real problem. The only way to predict this is with full correction with full correction in placein place in the trial frame in the trial frame under binocular condition and ask the patient under binocular condition and ask the patient about any distortion.about any distortion.


6.6. If the patient is intolerant of the cylinder If the patient is intolerant of the cylinder correction, correction, contact lensescontact lenses will reduce the will reduce the distortion associated with the correction distortion associated with the correction of the astigmatism. of the astigmatism.

7.If the patient is equally intolerant of the 7.If the patient is equally intolerant of the distortion or incapable or intolerant of distortion or incapable or intolerant of contacts, consideration of refractive contacts, consideration of refractive surgery (LASIK) should be given.surgery (LASIK) should be given.

Treatment of AstigmatismSpectacle Lenses have an inverse proportion of correction

with the degree of astigmatism.• According to the type of astigmatism the corrective

lens will be determined:-1. Regular astigmatism :in which the two principle

meridians are at right angle and is susceptible to easy correction by cylindrical lenses.

2. Oblique astigmatism :in which the two principle meridians are not at right angle but are crossed obliquely , it is corrected by using spherocylindrical lenses ,it is not very common.

3. Irregular astigmatism :where there are irregularities in the curvature of the meridians so that no geometrical figure is formed ,and the correction is very difficult.

Treatment of Regular Astigmatism

Uncorrected astigmatism

Corrected astigmatism

Because the light is split into two separate foci in astigmatic eye, a lens with two different power curves is needed to correct the astigmatism. These lenses are called cylindrical Lenses.Because of the different powers, these lenses have a variable edge profile that is thinner in some places and thicker in others. These lenses are more complex and have to be of the highest optical quality in order to produce good vision for the astigmatic patient..

Spectacles

Treatment of Irregular Astigmatism

The optical treatment of all these varieties of irregular astigmatism is often unsatisfactory.

• The refraction must be estimated by a time-consuming method of trial and error, which is frequently unrewarding (unsatisfactory).

• Improvement with spectacle lenses will in many cases be disappointingly small, but determined attempts to improve the vision by this means should be made as the results may occasionally be surprisingly satisfactory.

Treatment of Irregular Astigmatism

• Typically in conical cornea but even in other cases with actual opacities present, an immenseهائل visual improvement may be obtained by employing hard or semi-soft contact lenses.

• In other cases where the condition is serious lamellar keratoplasty in central area of a conical cornea or excision of a scar and its replacement by a graft (Epikeratoplasty) is the most effective method of treatment.

Surgeries available for astigmatism

1. AK) (Astigmatic keratotomy

2. PRK 3. LASIK 4. Lens

surgery5. LASEK6. Intacs

Lecture 13

Corneal surgery1. Arcuate keratotomy involves making paired arcuate

incisions on opposite sides of the cornea in the axis of the correcting "plus" cylinder (the steep meridian). The resultant flattening of the steep meridian coupled with a smaller steepening of the flat meridian at 90 degree to the incisions reduces astigmatism.

• The desired result can be controlled by varying the length, depth of the incisions and their distance from the optical centre of the cornea.

• Arcuate keratotomy may be combined with compression sutures placed in the perpendicular meridian, when treating large degrees of astigmatism such as may occur following penetrating keratoplasty.


•2 .PRK can correct up to 3D.• Since the advent of LASIK the procedure

is being performed less frequently and is largely reserved for patients who are unsuitable for LASIK .

• 3. LASIK can correct up to 15D.


4-Lens surgery :• Involves using a toric intraocular implant at the

time of cataract extraction. However, postoperative rotation of the implant away from the desired axis may occur.

• Lens surgery involves:A-Removal of the crystalline lens without I.O A-Removal of the crystalline lens without I.O

Lens implantation.Lens implantation.B- Nonremoval of the crystalline lens with I.O B- Nonremoval of the crystalline lens with I.O

Lens implantationLens implantation

Non corneal interventionNon corneal intervention A) Removal of lens was attempted occasionally A) Removal of lens was attempted occasionally

in the past to neutralize high myopia.in the past to neutralize high myopia.The operation is hazardous since it may cause :The operation is hazardous since it may cause :1.1. Vitreous lossVitreous loss2.2. Retinal detachment.Retinal detachment.3.3. Loss of accommodationLoss of accommodation4.4. Near work should be restricted.Near work should be restricted.5.5. Illumination must be good, print should be large.Illumination must be good, print should be large.B) Nonremoval of the crystalline lens with I.O B) Nonremoval of the crystalline lens with I.O

Lens implantation in AC to decrease the Lens implantation in AC to decrease the refractivity of the eye.refractivity of the eye.

Astigmatic keratotomy( AK)

• Astigmatic keratotomy is a variation of RK (radial keratotomy), used to treat astigmatism.

• AK uses arc-shaped incisions in the cornea, whereas RK uses radial incisions, like the spokes of a wheel. Neither RK nor AK is performed with a laser.

Glare at night can also be expected for the same length of time. Some patients have complained for up to 3 years. However, glare testing shows no significant glare after 1 year in 99.3% of the cases. Approximately 83% of patients in the expected range achieve unaided post-operative 20/40 (or better) vision.

The Procedure Of AK

The patient is given a mild sedative prior to surgery and the eye is prepared normally. Generally, the non-dominant eye is selected for the first operation , with an average minimum wait of one week before surgery is performed on the dominant eye.

•During the operation, the front surface of the eye is numbed with drops (TOPICAL ANAESTHESIA). •Some surgeons advocate retro-bulbar anesthesia. •A mark in a spoke-like pattern is then impressed the cornea. This is temporary and is used for marking where the surgeon will make the incisions. The marks are based upon a formula determining your prescription, age, and the amount of correction needed.

The Procedure Of AK

The Procedure Of AK

The surgeon will then make several incisions (keratotomies) in the cornea using a microscope and a microscopic surgical instrument that has a diamond tip. This diamond instrument has a safeguard which prevents it from penetrating into your eye. The actual surgery time takes about 5 minutes but with pre-operative preparations it can take up to an hour.

Precise microscopic control must be maintained over the length, depth, and arrangement of these micro-incisions in order to achieve proper optical correction. These micro-incisions allow the central cornea to be regular, removing the asymmetric shape that causes astigmatism, thus partially or completely correcting the vision impairment.

The Procedure Of AK

The Procedure Of AK

• Antibiotic and cycloplegic drops are then applied and the lid speculum removed.

• A patch is then placed on the eye for approximately 2 hours.

• Other than diligent . متقن care to مجتهدavoid getting the eye patch soiled or wet, there are no restrictions placed on the patient.

• Antibiotic drops are used for l-2 weeks after the surgical procedure.

After Operation

1-For the first 24 hours after the surgery, the patient may experience some sensitivity to light, mild scratchiness, and/or redness in the operated eye.2-There may also be some pain which is usually alleviated by common, pain killer medication.3-Vision is usually good within the first week, but fluctuation of visual acuity from morning to night can be expected for up to 6 months or longer. Occasionally, a second operation is needed to reduce any residual myopia.

PRK: Photorefractive Keratectomy

PRK: Photorefractive Keratectomy uses the cool beam of the excimer laser to reshape the front of the eye by treating the surface of the cornea so that light rays focus more sharply on the retina. The outer surface of the cornea, called the epithelium, must be removed.

This is accomplished by carefully scraping it away. The laser is then applied to remove microscopic amounts of corneal tissue, measured in microns.

PRK: Photorefractive Keratectomy

• The epithelium grows back over the treated area within several days. A "bandage" contact lens is placed on the eye to minimize discomfort during this healing period.

• Complete healing and visual recovery can take as long as 3-6 months with PRK.

Excimer laserPHOTOREFRACTIVE

KERATECTOMY• The excimer laser makes pulses of

invisible ultraviolet light. Each pulse of light removes a microscopic layer from the corneal stroma, changing the curvature of the cornea ever so slightly.

PHOTOREFRACTIVE KERATECTOMY

• To correct nearsightedness, the curvature of the cornea must be decreased the cornea must be made flatter.

• To correct farsightedness, the curvature of the central cornea must be increased.

• To correct astigmatism, the curvature must be altered in one specific direction.


• Low amounts of nearsightedness, astigmatism or farsightedness, will require smaller amounts of tissue removal, and larger corrections will require greater amounts. The total treatment usually takes less than one minute of actual laser time


• A computer running specialized software determines the exact pattern of pulses needed to remove the right amount of corneal tissue. The computer also directs the actual operation of the laser system.

PHOTOREFRACTIVE KERATECTOMY DISADVANTAGES AND COMPLICATIONS

• 1-Discomfort is very minimal during or after the procedure.

• 2-Fewer than 2% report any kind of pain. • 3-It is normal to have a sensation of dryness or

"tired eyes" after surgery. This sensation diminishes with time.

• 4-The eyes may be red following the procedure. This redness is harmless, and will fade within a few days.

PHOTOREFRACTIVE KERATECTOMY DISADVANTAGES AND COMPLICATIONS

5-Many people will experience glare or haloes at night for a few weeks to several months postoperatively. This diminishes, and in most cases will disappear entirely over time.

6-Undercorrection or overcorrection

If any of the following conditions apply to you, then you are NOT a good candidate for PRK

Contraindications of PRK1. KERATOCONUS.2. High I.O.P3. Intraocular inflammation4. Weak cornea due to local or general

disease5. Cataract

6.Pregnancy.7. Unstable refractive error (your vision has

been changing over the past 12 months).8. Collagen/Vascular disease. 9. Active ocular disease.10. Under 18 years of age.11. Pacemaker users.

Contraindications of PRK

الليــزك LASIK عمليــــة Laser in-situ keratomileusis

أشعة • تسليط عملية عن عبارة هي اـلليزك عمليةحيث اـلداخلية، القرنية طبقـات على اإلكزيمرـليزرالقطع جهـاز بوساطة القرنية من جزء قطع يتم

بمقدار ثني 270اإللكتروني يتم ذلك وبعد درجة،الطبقات على اـلليزر أشعة وتسليط المقطوع اـلجزءالمقطوع الجزء إعـادة يتم ذلك بعد للقرنية، اـلداخلية . خيـاطه بدون الطبيعي مكانه إلى القرنية منLASIK combines the precision of the excimer laser that is used in PRK surgeries with the flap technique that characterizes this surgery.

LASIK SurgeryLaser in-situ keratomileusis

There are FDA regulations governing which particular excimer laser may be used to correct which particular type and degree of refractive error. For instance, one excimer laser was recently approved for LASIK treatment of nearsightedness up to -14.0 diopters with or without up to -5.0 diopters of astigmatism. These are high amounts of refractive error and include most nearsighted people. But there are quite a few people with more than -14.0 diopters of nearsightedness, and the FDA feels they will not achieve a satisfactory result.

LASIK

LASIK FACTS• Range of Correction: LASIK, Laser

Assisted In Situ Keratomileusis, is state-of-the-art in refractive surgery. It is used to correct nearsightedness up to 20 diopters, farsightedness up to 5 diopters, and astigmatism up to 5 diopters

LASIK

• However with LASIK, the epithelium is not removed. Instead, using a precision instrument called a microkeratome, a hinged flap consisting of an extremely thin layer of epithelial tissue is created.

• This flap is then gently folded back out of the way while precisely measured pulses of cool laser light are applied to the underlying tissue.

LASIK

• The non-thermal laser breaks the molecular bonds of corneal cells, which are vaporized a layer at a time, until the desired correction is achieved. These changes to the cornea are so minute that they must be measured in microns…thousandths of a millimeter (It would take 200 pulses of the laser to cut through the thickness of a single human hair!)

LASIK

• Afterward the flap is carefully repositioned where, thanks to the remarkable natural bonding qualities of the corneal tissue, it adheres and quickly heals without the need for stitches. Drops to prevent infection may be used for a few days following LASIK.

LASIK• Where is it done? LASIK is performed as

an outpatient procedure with topical anesthetic and a mild sedative. It takes about fifteen minutes per eye, with both eyes being done on the same day.

LASIK• Age is a factor: We do not offer LASIK to

anyone under 18. Young people's eyes are often still changing rapidly. A stable eyeglasses prescription (no significant changes in the past two years) is important to a good outcome.

LASIK• During the use of the microkeratome some

patients notice a sensation of pressure and a "graying" of vision, associated with a "suction ring" which holds the eye steady.

LASIK• Recovery with LASIK is very rapid. Most

people achieve good, functional vision and can go back to work within 2 days.

LASIK Results• The results are even better: 96% of the patients

achieve 20/20 or better vision without glasses, with 99% of the patients achieving 20/25 or better vision. After the initial treatment, 90% of patients will have 20/25 or better vision without glasses, and 99% will have 20/40 or better vision without glasses. 20/40 vision is good enough to pass the driver's vision test without glasses For patients with mild nearsightedness, farsightedness, or astigmatism, the results are even better. Patients requiring higher amounts of correction will have less accurate results.

LASIK Advantages• 1-The quality of vision after laser vision

correction is usually superior to vision with contact lenses or glasses.

• 2-Patients generally have less glare than they had with contact lenses

• 3-The inconvenience and discomfort of contact lenses is eliminated.

• 4-Side vision isn't blocked, as it is with glasses• 5- There is no longer the problem of dirty, wet or

scratched glasses.

RESULTS

• 6-The vast majority of patients no longer need glasses or contact lenses for distance vision after laser vision correction treatment.

PRK versus LASIK: Comparisons

range of correctionPRKLASIK

low to moderatelow to severewound depth superficial20% deep

intraoperative pain nonenonepost-operative

medications 3 months, possibly more1-2 weeks

functional vision recovery

3 to 5 days24 hours

Corneal epitheliumCompletely removedCompletely repositionedvisual results fully

recognized3 weeks to several

months1 to 4 weeks

return to work3 to 5 days1 day risk of complicationslow (more surgeon

dependent)low (less surgeon

dependent)risk of scarring in

central cornea1-2 % <1%

لعملية التحضيرية الخطواتالليزك

Indications and Contraindications Of LASIK ،الليزك لعملية التحضيرية الخطوات الجدول يبين

بفحص القيام وتستدعي مطولة خطوات وهيأن معه يستغرب ال مما للعين ودقيق كامل

ما تتراوح طويلة مدة التحضير عملية تستغرق . الزمن من ساعتين إلى ساعة بين

أهم من واحد للعين الطبوجرافي للتصوير صورةوالليزك الليزر لعمليات التحضيرية الفحوصات

العين ضغط 1قياس

قبل عينه ضغط المريض يعرف أن المهم منحقيقي غير انخفاضا هناك ألن الليزك، عمليةضغط يكتب العملية إجراء بعد العين لضغط

العين ضغط يقال فمثال باألرقام 17العينللعين الطبيعي الضغط بأن علما زئبق مليمتر

زئبق 19إلى 11من مليمتر

للعين الطبوجرافي 2التصوير

قبل أساسي متطلب للعين الطبوجرافي التصوير . يوجد التي العين الستبعاد وذلك العملية إجراء . تبين ملونة صورة مخروطية قرنية اشتباه بها

للعين الطبوجرافي الشكل

The Before image is relatively steep, as indicated by the green and yellow colors. This patient also had astigmatism (irregularly shaped cornea) seen as an hourglass shape, in yellow.

After the procedure, topography shows a much flatter, and more even cornea. This patient had nearly 8 diopters of myopia and astigmatism corrected.

القرنية قياس 3سماكةPachymetry

إجراء من يمنع قد القرنية سماكة انخفاضمن يحد وقد األحيان، بعض في العمليةنظر قصر لديهم لمن الكامل التصحيح

باألرقام القرنية سماكة تكتب شديدالقرنية سماكة يقال مايكرون 520فمثال

االنكساري االنحراف 4قياس

ASTIGMATISMتحديد يمكن االنكساري االنحراف قياس على بناء

ونسبة عدمه من العملية إجراء إمكانية مدى . باألرقام المقاس يكتب إجرائها حال في النجاح

حالة في وكتابة ناقص أو زائد عالمة وضع معاالنحراف زاوية Axis of cylinder وجود

أخرى 5موانع

الطبيب يكتشفها قد أخرى موانع إلى باإلضافة هذا. العملية قبل العين على الكشف عند المختص

المزمن الفيروسي القرنية التهاب مثل

العين من األمامي الجزء 6فحص

من الجراح يمكن العين من األمامي الجزء فحصمن تمنع وقد العين تعانيها أخرى أمراض معرفة

وضع عن بيانات الفحص ناتج العملية إجراءالجزء وبقية والجفن والملتحمة والعدسة القرنية

العين من األماميAs iridocyclitis and corneal scarring and

keratoconjuctival sicca

العين قاع 7فحصفإنه الشبكية في ثقوب او امراض وجود حالة في

كما الليزك عملية في البدء قبل عالجها يلزملكل دوريا شبكية اختصاصي بمراجعة ينصح

العالي النظر بقصر المصابينالعصب وحالة الشبكية لشكل رسم الفحص ناتج

البصري´As complications of high myopia

قرب عن 8اإلبصارPresbyopia

من يقتربون الذين لألشخاص مهم الفحص هذاالحتياجهم احتماال هناك إن حيث األربعين، سن

الليزك إجراء بعد قراـءة نظارة إلى

األلوان رؤية 9قياسColour vision

للخدمة المتقدمين تقبل العسكرية الكليات بعضرؤية تشترط ولكنها الليزك، عملية أجروا الذين

هذا أهمية جاءت هنا ومن لأللوان طبيعيةالفحص ناتج األشخاص من النوع لهذا الفحص

: طبيعية رؤية التالي النحو على عادة يكتبلأللوان طبيعية غير رؤية أو لأللوان

والسكري الحمل 10فحص

حين إلى الـعملية يؤجل قد مثال الحمل وجودالسكر مريض لدي السكري اضطراب الوضع،وجود مـعرفة وهكذا العملية إجراء من يمنع قد

أخرى باطنية أمراض

العام الصحى 11الوضع

المريض بين والتشاور الفحص من مهم جزء هذاالواقعية النتائج ومعرفة العملية قبل وطبيبه

تخيل المريض يجنب إليها، الوصول يمكن التيخالل من إليها الوصول يمكن ال مثالية توقعات

المضاعفات ونسب النجاح نسب معرفة العمليةالعملية عقب الرؤية الستقرار المتوقع والوقت

وبعدها العملية قبل اتباعها المطلوب والتعليمات

القرنية تحدب 12قياسKeratometry

حدوث احتمال من يزيد قد القرنية تحدب ارتفاعالكبير االرتفاع أن كما العملية، خالل مضاعفات

تحديد مخروطية قرنية وجود ناتجا يكون قدما تكون العادة في والتي القرنية تحدب درجة

درجة 44-42بين

البؤبؤ قطر 13قياس

مستوى على يؤثر قد العين بؤبؤ قطر ارتفاعقطر معرفة الليزك عملية عقب الليلية الرؤية

بين يكون ما عادة العين مليمترات 7-5بؤبؤ

Health & Medicine

Retinoscopy