Dr Jusuf Wijaya , SpMFK - UKICawang

Curriculum Vitae1994 : Dokter Umum , Vrije Universiteit Brussel (Belgia)1999 : Dokter Spesialis Mata , Vrije Universiteit Brussel (Belgia)2001 : Fellow Ilmu Bedah , Foundation Eye Care Himalaya (Belanda Nepal)2002 : Fellow di bidang Glaukoma , Rotterdam Eye Hospital (Belanda)2004 : Adaptasi (penyesuaian) , Universitas Sam Ratulangi (Manado)

I.Fysiology of the Ocular Muscles Definition of StrabismusClassification of Strabismus

There are six extraocular muscles which act to turn or rotate an eye about its vertical, horizontal, and antero-posterior axes:1. Medial Rectus (MR)2. Lateral Rectus (LR)3. Superior Rectus (SR)4. Inferior Rectus (IR)5. Superior Oblique (SO)6. Inferior Oblique (IO)

The Six Extraocular Muscles

Nervus III : - Musculus rectus superior (1) - Musculus rectus inferior (2) - Musculus rectus medialis (3) - Musculus obliquus inferior Nervus IV : - Musculus obliquus superior(5)Nervus VI : - Musculus rectus lateralis (4)Nervus II :- N Opticus (7)

A given extraocular muscle moves an eye in a specific manner, as follows: 1. Medial Rectus (MR)- moves the eye inward, toward the nose (adduction)2. Lateral Rectus (LR)- moves the eye outward, away from the nose (abduction)3. Superior Rectus (SR)- primarily moves the eye upward (elevation) - secondarily rotates the top of the eye toward the nose (intorsion) - tertiarily moves the eye inward (adduction)

4. Inferior Rectus (IR)- primarily moves the eye downward (depression) - secondarily rotates the top of the eye away from the nose (extorsion) - tertiarily moves the eye inward (adduction)5. Superior Oblique (SO)- primarily rotates the top of the eye toward the nose (intorsion) - secondarily moves the eye downward (depression) - tertiarily moves the eye outward (abduction)6. Inferior Oblique (IO)- primarily rotates the top of the eye away from the nose (extorsion) - secondarily moves the eye upward (elevation) - tertiarily moves the eye outward (abduction)

Each extraocular muscle is innervated by a specific Cranial Nerve (C.N.): - Medial Rectus (MR) : cranial nerve III (Oculomotor) - Lateral Rectus (LR) : cranial nerve VI (Abducens) - Superior Rectus (SR) : cranial nerve III (Oculomotor) - Inferior Rectus (IR) : cranial nerve III (Oculomotor) - Superior Oblique (SO) : cranial nerve IV (Trochlear) - Inferior Oblique (IO) : cranial nerve III (Oculomotor)

DuctionsWhen considering each eye separately, any movement is called a duction.VersionsWhen considering the eyes working together, a version or conjugate movement involves simultaneous movement of both eyes in the same direction.

There are six principle versional movements where both eyes look or move together in the same direction, simultaneously: 1. Dextroversion (looking right)- right lateral rectus - left medial rectus2. Levoversion (looking left)- left lateral rectus - right medial rectus3. Dextroelevation (looking right and up)- right superior rectus - left inferior oblique

4. Dextrodepression (looking right and down)- right inferior rectus - left superior oblique5. Levoelevation (looking left and up)- right inferior oblique - left superior rectus6. Levodepression (looking left and down)- right superior oblique - left inferior rectus

VergencesA vergence or disconjugate movement involves simultaneous movement of both eyes in opposite directions.There are two principle vergence movements: - Convergence - both eyes moving nasally or inward - Divergence -both eyes moving temporally or outward

I.Fysiology of the Ocular Muscles Definition of StrabismusClassification of Strabismus

StrabismusStrabismus is a visual disorder where the eyes are misaligned and point in different directions. This misalignment can occur part of the time (intermittent) or all of the time (constant).

Strabismus occurs in approximately 2% of children under 3 years of age and about 3% of children and young adults, affecting boys and girls equally.

StrabismusNormal alignment of both eyes during childhood allows the brain to fuse the two pictures into a single 3-dimensional image. This allows a high degree of depth perception.

Strabismus (heterotropia)Normally, when viewing an object, the lines of sight of both eyes intersect at the object; that is, both eyes point directly at the object being viewed. An image of the object is focused upon the macula of each eye, and the brain merges the two retinal images into one.Sometimes, however, due to some type of extraocular muscle imbalance, one eye is not aligned with the other eye, resulting in a strabismus, also called a heterotropia or simply tropia.

In children, when the two eyes fail to focus on the same image, the brain may learn to recognize the stronger image and ignore the weaker image of the amblyopic eye, to avoid double vision. If this is allowed to continue, the eye that the brain ignores will never see well. This loss of vision is called amblyopia.Amblyopia results if vision from one eye is consistently suppressed and the other eye becomes dominant.Among children with strabismus, one-third to one-half develop amblyopia.

If strabismus develops for the first time in adulthood, the affected individual usually experiences double vision ; diplopia .Because the brains of adults are already developed for vision, the problems associated with amblyopia, in which the brain ignores input from one eye, do not occur with adult strabismus.

I.Fysiology of the Ocular Muscles Definition of StrabismusClassification of Strabismus

III.Classification of Strabismus

1. Classification according to the direction of misallignment2. Other classification :Strabismus ParalyticansStrabismus Concomitans

Strabismus is classified according to the direction of misalignment.When one eye is looking straight ahead;- the other eye may turn inward (esotropia or convergent strabismus)- outward toward the ear (exotropia or divergent strabismus)- downward (hypotropia)- upward (hypertropia).

This child has a right esotropia. The child is looking at you with their left eye. The right eye is turned in towards the noseIn the right picture, the child is fixating with their right eye. In this position, it is the left eye which is esotropic. A child can be made to alternate between the eyes simply by covering the left eye when it is fixating (left picture) thus forcing the right eye to fix (right picture). The ability of the child to keep either eye in the straight ahead position for a while indicates that there is no weakness of vision in either eye.

Pseudoesotropia is a common condition in infancy and early childhood in which the child appears to have crossed eyes due to a wide bridge of the nose and/or epicanthal folds. This causes the medial sclera to be hidden when the child looks just off centre and therefore the eyes appear to be crossed.This patient may look like he has crossed eyes but in fact the eyes are straight.

Exotropia (picture on the left)Hypertropia (picture on the right)

Acquired strabismus in adults can be caused by:- injuries to the orbit of the eye- braininjury (including closed head injuries and strokes).People with diabetes often have loss of circulation causing an acquired paralytic strabismus.Loss of vision in one eye from any cause will usually cause the eye to gradually turn outward (exotropia).

Strabismus can be caused by :- problems with the eye muscles- problems with the nerves that control the eye muscles- problems with the brain, where the signals for vision are processed.Strabismus can accompany some illnesses such as:- high blood pressure- multiple sclerosis- myasthenia gravis- thyroid disorders.