Myopia

MYOPIAکارشناس – محمدپور مجتبی اپتومتری اپتومتریست ارشد

اپتومتریست مجتبی محمدپور کارشناس ارشد اپتومتری

mojtaba mohammadpour .optometrist,Msc.univercity of medical scences Birjand ,Iran

• EMMETROPIA

Parallel incident rays come to a focus on the retina

when the accomodation is fully relaxed so far point is at

infinity.

MYOPIA

eye having excessive refractive power for its axial length.(borish)

This may be due either to the eye having 1-a relatively long axial length 2-increased dioptric power of one or more of the refractive elements.

myopia

Far point of the eye closer to retina than infinity

• Axial myopia • if the total refractive power of an eye remains constant but the

axial length (i.e., the distance from the anterior corneal surface to the retina measured along the visual axis) increases, a myopic shift in refractive error will result

• Refractive myopia• if the axial length of an eye remains constant but the

refractive power of one or more of its optical elements increases, a myopic shift in refractive status will occur.

MYOPIA: REFRACTIVE vs AXIALRefractive Myopia

(Optics of the eye too strong)

Axial Myopia

(Eye too long)

• The proposed classifications may be grouped under the following broad headings:

• 1-Rate of myopic progression• 2-Anatomical features of myopia• 3-Degree of myopia• 4-Physiological and pathological myopia• 5-Hereditary and environmentally induced myopia• 6-Theory of myopic development• 7-Age of myopia onset

• Classification by Rate of Myopic Progression

• 1-Stationary myopia

• 2-temporarily progressive

• 3-permanently progressive.

• 1-Stationary myopia Stationary myopia• (Donders )

• is generally of low degree (-1.50 to -2.00 D) and arises "in the years of development."

• The degree of myopia remains stationary during adulthood and may occasionally diminish with the approach of old age.

• 2-temporarily progressive• Temporarily progressive myopia generally arises in the early

teens and progresses until the late 20s.

• After this age, the rate of myopia progression approaches zero. Interestingly, Donders reported that it was rare for myopia to develop after 15 years of age in previously normal eyes and, falsely, that it never developed after the 20th year of life

• 3-permanently progressive• Permanently progressive myopia ascends rapidly until

around 25 to 35 years of age, and there afteradvances more slowly.

• Subsequent increases in myopia are said to occur in jumps, rather than in a smooth progression.

• Donders observed that because of pathological condi-tions such as retinal detachment and macular degener-ation, in these cases it was rare at 60 years of age "to find a tolerably useful eye."

• Classification by the Anatomical Features of Myopia

• 1-Axial• whereby the eye is too long for its refractive power

• 2-Refractive

• whereby the refractive system is too powerful for the axial length of the eye.An increase in axial length may occur in the anterior or posterior portions of the globe individually, or may occur throughout the eye.

• The site of elongation may have implications for determining the etiology. For example, it has been suggested that expansion of the posterior portion of the globe may be related to the actions of the superior and inferior oblique muscles during vergence

• Borish further divided refractive myopia into

1-Index myopia• in which one or more of the refractive indices of the media are anomalous.

• 2-Curvature myopia,• in which the reduced radius of curvature of one or more refractive surfaces produces

increased dioptric power.

• 3-Anterior chamber myopia in which a decrease in anterior chamber depth increases the refractive power of the eye.

• Hirsch examined the refractive error of 562 eyes having myopia in patients between 18 and 60 years of age. He divided the population into three groups on the basis of the degree of myopia,

• 1-alpha• Using inferential statistics, he determined that the alpha group followed a

normal distribution curve, with a theoretically assumed peak of -0.50 D.

• 2-beta groups

• The beta group was represented by a second normal distribution curve, with its peak around -4 D.

• Hirsch suggested that the myopia in this group may be hereditary in origin

• 3-gamma groups

• The gamma group ranged from -9 to -15 D, and this degree was described by Hirsch as malignant, pathological, degenerative, or congenital.

• Sorsby et al in an investigation of 341 eyes between 20 and 60 years of age, concluded that 95% of refractive errors fell within ±4 D. They also suggested that the etiology of myopia of less than 4 D differed from that myopia exceeding 4 D,

• Classification Based on Age of Onset

• 1-Congenital myopia:• Myopia is present at birth and persists through infancy .although many children are born with

myopia (low birth weight) lose their myopia during first year of life this classification includes only children whose myopia persist in infancy and present when entering school. prevalence is about 2%.

• 2-Youth-onset myopia:• The onset of myopia occurs between 6 years of age and the early teens .from 2% at 6 years to

20% at 20 years.

• 3-Early adult-onset myopia:• The onset of myopia occurs between 20 and 40 years of age.

• 4-Late adult-onset myopia:• Myopia onset occurs after 40 years of age.

• Physiological (correlation ) myopia • All of the component of refraction are within normal limits .but lack of

correlation.(-0.50D) per years.

• intermediate myopia• Similar to Physiological myopia but • 1-age is slightly younger.• 2-amount of myopia tends to be higher.• 3-axial length is longer.

• Pathologic myopia • Highly myopic refractive error is present from early

childhood and is progressive. prognosis is poor with legal blindness

• Other Myopias

• Night Myopia• The phenomenon of increased myopia under low luminance

conditions was first reported in 1789 by the Revere and Nevil Maskelyne

• More recent evidence has demonstrated that night myopia is produced by an increased accommodative response (typically on the order of 0.50 to 1.00 D) under degraded stimulus conditions changes in chromatic aberration may also be involved in this myopic shift.

• Pseudomyopia

• Pseudomyopia has been defined as a reversible form of myopia that results from a spasm of the ciliary muscle.

• The excessive accommodative response produces an apparent myopic shift that will disappear when a cycloplegic agent is administered to produce relaxation of accommodation

Ocular disorder Associated with Myopia

• 1-Retinopathy of prematurity• 2-retinitis pigmentosa• 3-Albinism• 4-Congenital or juvenile glaucoma• 5-keratoconus• 6-isolated ectopic lentis• 7-CSNB• 8-subset of Lebers s Congenital amaurosis• (majority are hypropic)• 9-Cone dystrophy• 10-Interruption of light passing through ocular media• 11-Genetics! autosomal dominant pathologic myopia to gene18p11.31

• • 6-Cataract -Nuclear cataract causes a myopic shift

Retinopathy of prematurity

• 1-VEGF

• Treatment• 1-laser photocoagulation • 2-anti VEGF (bevacizumab )

AlbinismAlbinism, a group of inherited disorders, results in little or no production of the pigment melaninFoveal hypoplasiaTyrosine negative –positive

Systemic disorder Associated with Myopia

• 1-Marfan’s syndrome• 2-Down syndrome• 3-Fetal alcohol syndrome• 4-Ehler’s-Danlos syndrome• 5-homocysinuria• 6-Stickler’s syndrome• 7-weill – marchesani syndrome

• 4-Congenital or juvenile glaucoma• 5-keratoconus• 6-isolated ectopic lentis• 7-CSNB• 8-subset of Lebers s Congenital amaurosis• (majority are hypropic)• 9-Cone dystrophy• 10-Interruption of light passing through ocular media• 11-Genetics! autosomal dominant pathologic myopia to

gene18p11.31

Marfan syndrome most often affects the connective tissue of the heart and blood vessels, eyes, bones, lungs, tall, thin build.• Long arms, legs, fingers, and toes and flexible joints.• A spine that curves to one side. This condition is called scoliosis .• A chest that sinks in or sticks out. These conditions are called pectus

excavatum and pectus carinatum respectively.• Teeth that are too crowded.• Flat feet.

Pathological Conditions Associated with Myopia

• Marfan’s syndrome– Suspensory ligaments break– dislocation of lens occurs superiorly and temporally and

results in a very high increase in myopia

Lens dislocation is common in Marfan's, affecting 50% to 80% of patients. The dislocation is usually superior

• Marfan's syndrome is an autosomal dominant disorder caused by mutations in the fibrillin gene on chromosome 15.

• Fibrillin is a glycoprotein that is a major component in elastic tissue and is important in lens zonules. 50-80 percent of patients with Marfan’s syndrome have ectopia lentis.

Aortic root dilationm.v.p

Unlike Marfan syndrome, in which the joints tend to be "loose," in homocystinuria the joints tend to be "tight."

rare inherited metabolic disorder involving the amino acid methionine and resulting in a harmful accumulation of homocysteine in the body.

Mental retardation Skeletal abnormalities Scoliosis Kyphosis Chest abnormalities

homocysinuria

Stickler syndrome

• Stickler syndrome is a

• connective tissue disorder• a genetic malfunction in the connective tissue• bones• Eyes• and ears• flattened facial appearance.• abnormal curvature of the spine (scoliosis or kyphosis)

• Ocular disorder

• glaucoma• Cataracts• retinal detachment

Ehlers-Danlos syndrome

Ehlers-Danlos syndrome is a group of inherited disorders that affect your connective tissues — primarily your skin, joints and blood vessel walls.

Ehlers-Danlos syndromeSkin thin and hyperelastic

Weill–Marchesani syndrome short stature; an unusually short, broad head (brachycephaly) facial abnormalities; hand defects, including unusually short fingers (brachydactyly); distinctive eye abnormalities.

A six year old female with Weill-Marchesani syndrome, which has caused a dislocated lens.

Weill–Marchesani syndrome

• microspherophakia• myopia• lens subluxation• and glaucoma secondary to progressive

shallowing of the anterior chamber.

A lens dislocation caused by Weill-Marchesani syndrome

A lens dislocation caused by Weill-Marchesani syndrome

Pathological Conditions Associated with Myopia

• Diabetes– High blood glucose levels cause increased sorbital levels in

the lens– Water rushes in and dilutes the sorbital in the lens– Lens bulges and results in a myopic shift

• Classification into

• Physiological

• Pathological Myopias

• 1-Physiological myopia

• was denned by Curtin as myopia in which each component of refraction lies within the normal distribution for that population. Thus, the myopia arises from a failure of correlation between the refractive components.

• However, physiological myopia may be defined as normal as opposed to pathologic myopia Therefore, physiological myopia might simply and more accurately be defined as nonpathological myopia

• 2-Pathological Myopia(malignant or degenerative myopia)

• Duke-Elder and Abrams defined pathological refractive errors as "those refractive• anomalies determined by the presence in the optical system of the eye of an

element which lies outside the limits of the normal biological variations.

• These authors adopted the term degenerative myopia to describe myopia that is accompanied by degenerative changes, particularly in the posterior segment of the globe. This is most frequently found in high (>6 D) degrees of myopia

Pathologic Myopia

Eyes with pathologic myopia have progressive elongation of the eye, thus creating a propensity for thinning of the RPE and choroid

The spherical equivalents of an eye with high myopia are more than -6.00 D, or an axial length greater than 26.5 mm, whereas patients with pathologic myopia are more than —8.00 D, or an

axial length greater than 32.5 mm.

• Degenerative myopia is also known as other terminology including:

• High Myopia• Degenerative Myopia• Pernicious Myopia• Malignant Myopia

• Pathological change in myopic eyes

• TOOLS TO MONITOR

• Fundus photography• A- and B-scan ultrasonography• Visual fields• OCT• Monitor corneal health if CL wearer• Fundus photos

• FUNDUS SIGNS•

It is important as primary eye care providers to be cognizant of the signs of degenerative myopia which commonly include:

• Tilting of the optic disc• Peripapillary chorioretinal atrophy• Lacquer cracks• Round, subretinal hemorrhages that clear spontaneously• Fuchs spots + CNV• Posterior staphyloma• Paving-stone degeneration • lattice degeneration• Hole formation in the peripheral retina• Elongation and atrophy of the cilliary body• POAG

TIGROID FUNDUS

• As the eye enlarges, the retinal pigment epithelium thins, resulting in a tessellated (checkered) appearance of the fundus and increased visibility of the choroidal vasculature.

TIGROID FUNDUS: As the eye enlarges, the retinal pigment epithelium thins, resulting in a tessellated (checkered) appearance of the fundus and increased visibility of the choroidal vasculature.

Myopic crescent

• a white or grayish white crescentic area in the fundus of the eye located on the temporal side of the optic disc; caused by atrophy of the choroid, permitting the sclera to become visible.

Optic disc crescents are common in myopes. They can vary in size and locationbut are typically situated at the temporal disc margin as in this three dioptre myope.

A much larger crescent in a nine dioptre myope

Myopic crescent

• Posterior Staphyloma

• The posterior staphyloma is a pathognomonic feature of eyes with pathologic myopia. It is a localized

• ectasia of the sclera, choroids, and retinal pigment epithelium that can be of variable size and involve different aspects of the posterior fundus.

• These staphylomas are best observed with indirect binocular ophthalmoscopy and B-scan ultrasonography.

• The posterior staphylomas are usually present from a young age and• may progress with age, particularly with high myopias and long axial• lengths.

• Vision progressively deteriorates in eyes with staphylomas that amacula-centered because of the progressive thinning of the choroids and

• retinal pigment epithelium in the macula.

POSTERIOR STAPHYLOMA: Staphylomas are localized ectasia (“enlargement”) of the sclera, choroid, and RPE. It can be easily seen on B-scan or a CT Scan. Staphylomas can eventually lead to atrophy and loss of vision.

The most common type 1 posterior staphyloma. The edge of thestaphylomatous region is arrowed

Lacquer Cracks• With the thinning of the retinal pigment epithelium and

choroid,ruptures of Bruch’s membrane occurs in up to 4.2%.

• These typically occur with a streak of retinal hemorrhage that is not associated with any underlying choroidal neovascularization.

Lacquer Cracks

• The lacquer cracks are best defined as linear hyperfluorescence in the early phase of fluorescein angiography and late hypofluorescence on indocyanine angiography.

• Over time, the cracks may widen and join with areas of atrophy. Central vision may be affected depending on the course of the lacquer crack, especially if there is foveal involvement. It should be noted that the presence of lacquer cracks does put the eye at risk of choroidal neovascularization.

• In our series of 28 Asian eyes with myopia of greater than –6.0 DS, sixeyes (21.4%) were found to have lacquer cracks as the underlying cause.

LACQUER CRACKS: are spontaneous ruptures of the elastic lamina of Bruch’s membrane that appear yellowish-white and are usually located in the posterior pole. They generally have linear or stellate patters. IVFA will show hyperfluorescence, as the fluorescein leaks through Bruch’s membrane, highlighting these cracks. These can lead to CNV in the 4th-6th decade of life.

Myopic macula chorioretinal degeneration with lacquer crack across the fovea.

Lacquer cracks near the macula

Myopic Foveoschisis

• As a consequence of the ectasia secondary to the posterior staphyloma,highly myopic individuals can develop foveoschisis.

• This is the splitting of the retinal layers in the macula which can cause blurring of vision and metamorphopsia.

• It can then progress on to a myopic macular hole formation that may be associated with a retinal detachment

• .Surgical intervention may be necessary to restore the anatomy and visual function. The surgical procedures that have been performed include vitrectomy with gas tamponade and macular buckling.

• Postsurgical developments in a myopic macular hole with associated retinal detachment. (a) Posterior pole of the left eye shows a tilted optic disc with myopic crescent, and a horizontally oval macular hole with extensive subretinal fluid, which masks the retinal pigment epithelial (RPE) atrophy around the hole. Subretinal precipitates suggest chronicity of the retinal detachment. (b) Optical coherence tomogram (vertical 10 mm scan) shows the macular hole, the surrounding sensory retinal detachment, and the posterior staphyloma. (c) One month after vitrectomy, the retina is reattached with closure of the macular hole. The central geographic patch of RPE atrophy is now prominent. (d) Repeat OCT (10 mm horizontal scan) confirms the anatomical outcomes; and reveals the residual central defect between the flattened edges of the macular hole ('flat open' configuration), as well as the presence of posterior staphyloma. Central sub-RPE hyperreflectivity is suggestive of geographic atrophy. (e) A small blister is evident within the nasal edge of the closed hole as early as 4 months on repeat mode OCT, which, however, disappeared on subsequent visits. (f) In a 4-year review, a full-blown foveoschisis has developed, with irregular but attached central edges. Status quo continued for 6 months.

tilted optic disc with myopic crescentmacular hole

Color fundus photo of a highly myopic patient who presented with progressive reduction in vision. Notice the significant myopic degeneration in the posterior pole. The patient was found to have myopic foveoschisis (MF) with foveal detachment.

• OCT AND MF• The standard test to detect MF remains OCT

Clinical photographs of the fundus of the right (A) and (B) left eyes in a patient with MFS. (c) Fluorescein angiogram of the right eye in the early (C) and late (D) phases, demonstrating staining of the optic nerve crescents and small window defects along the macular region.

On OCT scans

• eyes with MF exhibit a thickened retina in the posterior pole and hyporeflective splitting between the less reflective outer retina and the more reflective inner retina.

•

There is splitting of the retinal layers of the macula in the presence of myopicfoveoschisis as seen on this OCT scan.

SD-OCT image of a 60-year-old woman with high myopia and posterior staphyloma demonstrating typical MF (large arrow), premacular structure (small arrow), and foveal detachment (star).

• Lattice degeneration

• Lattice degeneration is a peripheral vitreoretinal thinning that is clinically• important because of the potential risk of developing retinal tears and• detachments.

• Lattice lesions can vary in their appearance. They can be linear or oval• lesions of retinal thinning that can be of various sizes and extents of

pigmentation.

• They are usually anterior to the equator

• Some may have round atrophic holes within them.• • These are not considered to be major risk factors for retinal detachment,

however,lattice degeneration has been reported in up to 20% of all detachments,and Byer showed that the risk of developing retinal detachment in the presence of lattice degeneration is about 0.3 to 0.5%.

LATTICE DEGENERATION: is a vitreo-retinal degeneration that causes retinal atrophy (“thinning”). It can be classified as pigmented or non pigmented. It takes on a lattice formation (“crisscrossing”) because the retinal vessels become sclerotic, and the collagen is laid down in this crisscross pattern. Due to the retinal thinning, it is prone to causing retinal breaks, tears, or holes, which of course might lead to retinal detachment. However it is important to remember that retinal breaks due to lattice degeneration rarely turn into retinal detachments.

Lattice Degeneration

Peripheral lattice degeneration with pigmentation and an atrophic round hole within.

Figure 9. Retinal detachment involving the macula secondary to multiple retinal breakssuperiorly.

Prevalence of fundus changes in 1584 consecutive eyes with high myopia

Fuchs’ spot• The most serious outcome of myopic chorioretinal degeneration is the

presence of a Fuchs’ spot, which is a round or elliptical, circumscribed lesion in the macular or perimacular area.

• It occurs as a result of breaks in Bruch’s membrane and the development of a neovascular membrane, giving rise to a hemorrhage that becomes pigmented.

• A Fuchs’ spot initially causes symptoms of metamorphopsia - as found on the Amsler grid - and can eventually cause a partial or complete loss of central vision.

FUCHS SPOTS: Fuch’s spots are dark spots due to RPE hyperplasia. They can involve subretinal neovascular membrane with an overlying retinal pigment epithelial hyperplasia. The CNV can eventually cause disciform scars on the macula in the 4th-6th decade of life.

A developing Fuchs’ spot together with haemorrhage and a serous detachment ofthe macula. Vision was markedly reduced

Paving Stone Degeneration

• well-delineated, flat yellow foci in the size range of 0.5–2.0 disc diameters .

• Irregular black pigmentation frequently is present on the margins of the lesions and red lines, which correspond to choroidal blood vessels

Pavingstone degeneration (also known ascobblestone) (Image courtesy of Dr HD Riley andthe Indiana University School of Optometry, USA)

Myopic Chorioretinal Atrophy

• The areas of atrophy may be focal or diffused, defined or irregularly• shaped, isolated or composed of multiple pale white areas in the

posterior pole

• . There may be clumps of pigment within these areas. • The choroidal vessels are usually easily seen beneath the thinned out

retina. Fundus fluorescein angiography would show staining of these atrophic areas while they are hypofluorescent with indocyanine green angiography.

• The natural history of these areas of atrophy is gradual enlargement• and coalescence. As the fovea becomes more extensively involved,

centralvision becomes progressively affected.

A myopic CNV which is seen as a greyish subfoveal membrane with surroundingsubretinal blood.

Fluorescein angiogram showing the classic CNV.

A 53-year-old female with myopia of –8.50 DS, presented with a subfoveal hemorrhagein the right eye with visual acuity 6/15 (a).

The fluorescein anigoram showed the presenceof a myopic CNV involving the macula (b).

(a) (b)

(c)

(d)(e)

The OCT scan showed the subretinal fluid space and the subretinal neovascular membrane (c). (d) and (e) She received a singledose of intravitreal bevacizumab 1.25 mg/0.05 ml and the vision improved to 6/9 after one month and this was maintained after 12 months. However there was formation of chorioretinalatrophy around the involuted mCNV (black arrow).

Myopic macular hole detachments

• Macular holes can develop in highly myopic eyes. This usually occurs as aconsequence of tractional forces from the vitreoretinal interfaceOften, a localized detachment arises within the macula, which over time,can extend peripherally

Myopic macular hole

Chorioretinal atrophy: larger geographic areas involving the posterior pole

. A myopic retina with a macular hole with surrounding retinal detachment within the macula

• Some unfortunate consequences of myopia

• 1-chorioretinal degeneration• 2-retinal detachment• 3-glaucoma• 4-cataract

Management

• Divergent or minus lenses in

• spectacles

• contact lenses

• Refractive surgery

• Low myopia <1.00 has little significant in infant and preschool children and is not usually corrected.

• Moderately low degrees of myopia (1- 3D) should be corrected in children who are 3 years of age or older.

• Moderately high degrees of myopia (3.00- 5.00D) should be corrected in children who are 1 years of age .

• high degrees of myopia (- 5.00D) should be corrected in any age .

• Bruce D.MOOR,OD. eye care for infants and young children.

Correction of myopia

1-minus glass2-contact lens

Uncorrected, light focuses in front of fovea

Corrected by divergent lens, light focuses on fovea

• Contact lenses

– Soft contact lenses– Rigid gas permeable contact lenses– Ortho-keratology contact lenses

Management

• Surgery

– Radial keratotomy (RK)• Post-surgical complications

– Hyperopic shift– Diurnal fluctuations of refractive error and visual acuity– Glare– Corneal scarring

Management• Refractive surgery– Photorefractive keratectomy (PRK)• Technique

– High energy photons from an excimer laser are used to photoablate a small amount of tissue from the anterior corneal surface and sculpt the cornea

Management

• Refractive surgery– Photorefractive keratectomy (PRK)• Post-surgical complications

– Eye pain– Corneal disruption– Blurry vision– Prolonged duration of drug use– Greater time needed for eyesight recovery

Management• Refractive surgery– Laser in-situ keratomileusis (LASIK)• Technique

– A microkeratome is used to cut a flap of superficial corneal tissue

– The flap is lifted back, exposing the underlying corneal stroma – The excimer laser is used to perform tissue removal in the

corneal stroma– The flap is repositioned in its original position and adheres to

the underlying corneal stroma without the need for sutures

Flap creation Laser intervention Flap repositioning

Management

• Refractive surgery– Laser in-situ keratomileusis (LASIK)• Post-surgical complications

– Severe dry eye syndrome– Poor night vision– Reduced contrast sensitivity– Astigmatism

Management

• Refractive surgery– Points to consider after the surgical procedure

• Use eyedrops, as prescribed by the ophthalmologist

• Wear sunglasses when outside to protect the eyes from sunlight

• Remember to go back to the hospital for regular follow up visits with the ophthalmologist and to get eyedrops

mojtaba mohammadpour .optometrist,Msc.univercity of medical scences Birjand ,Iran