SQUINT Strabismus Introduction: Six extraocular muscles insert in the sclera of each eye.. Normally they move the two eyes simultaneously, in a harmonious way so that the image of the object formed by each eye will lie at its fovea (Bifoveal Imaging)..

Extraocular Muscles

Sup. Rectus Oculomotor 1. Elevation (in abd.) Muscle Nerve Action . Sup. Rectus Oculomotor 1. Elevation (in abd.) 2. Intorsion 3 Adduction Inf. Rectus Oculomotor 1. Depression (in abd.) 2. Extorsion 3. Adduction Med. Rectus Oculomotor 1. Adduction Lat. Rectus Abducens 1. Abduction

L6SO4 3 Muscle Nerve Action . Sup. Oblique Trochlear 1. Depression (in add.) 2. Intorsion 3 Abduction Inf. Oblique Oculomotor 1. Elevation (in abd.) 2. Extorsion 3. Abduction L6SO4 3

Strabismus: Ocular misalignment, so that the image of an object does not fall on the fovea of both eyes simultaneously.. 2-5% of population Significance: 1. Common problem 2. It causes visual impairment. 3. May be caused by visual problem, e.g. hypermetropia, optic n. hypoplasia 4. Underlying serious pathology, e.g. Retinoblastoma 5. Cosmetic and social impact..

Squint (Strabismus)

Squint (Strabismus)

Pseuedosquint 1- Epicanthal folds: a prominent vertical fold of skin hanging over the inner canthus, and covering part of the nasal sclera  false impression of converging squint (Pseudo esotropia).. But normal results of squint diagnostic tests [ corneal light reflection, cover test].. More common in Orientals. usually lessen and may disappear with age Treat. 1. Reassurance 2. Some cases need plastic surgery, e.g. Z- plasty.

Epicanthal folds

2- Hypertelorism: Wide IPD  pseudoextropia 3-Macular Dragging (Heterotopia maculae): e.g.: ROP (Retinopathy of prematurity) Or Cong. Toxocara chorioretinitis

Hypertelorism

Classification of Strabismus 1- According to Direction: Eso deviation  Convergent squint the eye in turned inward Exo deviation  Divergent squint the eye in turned outward Hyper Hypo

Exo & Eso Squint

2- According to Severity: Tropia  Apparent squint Phoria  Latent squint (discovered only by cover test) e.g.: Rt. Esotropia = apparent convergent squint of the right eye..

A- Concomitant Squint: 3- Pathological classification A- Concomitant Squint: the angle of deviation of the squinting eye is constant on any direction of the gaze.. Early childhood + No correction  amblyopia and loss of binocular vision e.g.: - Congenital Esotropia - Accommodative Esotropia - Exotropia

B- Paralytic Squint (Incomitant): * Due to complete or partial palsy of one of the nerves that supply EOM. * Here, the angle of direction of gaze, being maximal in the direction of action of the weak muscle. Eg.: - Oculomotor Palsy  - Abducens Palsy  - Trochlear Palsy

Paralytic Squint

Congenital Esotropia 1st 6 months of life (Infantile/Essential) Large angle of deviation Concomitant [D.Dx: Abducens palsy] Refraction: normal or mild hypermetropia Needs surgical correction preferably to start before 12 months age

Accommodative Esotropia Concomitant 2-3 years Usually high degree of hypermetropia  excessive accommodation. (accompanied by convergence)  convergent squint which is more severe, or may be only present on looking at near objects. Usually treated with prescribing glasses with full cycloplegic correction of the refractive error (hypermetropia) for the child.. .. if fail  surgery..

Intermittent Exotropia: Concomitant diverging squint Periods of exotropia Fatigue Inattention, distraction Emotional upset May be myopic Treat.: full myopic correction with glasses + observation If attacks ↑ in frequency, or duration  surgery..

Intermittent Exotropia

Management of child with squint History: 1. Birth: prematurity, method 2.Medicalproblem,developmental abnormality 3. Age of onset 4. Direction 5. Constant or intermittent 6. Association with fatigue. 7. Family history

Examination: 1- General appearance: * craniofacial abnormality. * abnormal head posture  to avoid diplopia * epicanthal fold 2- Visual assessment: * different techniques * amblyopia 3- Corneal reflection test: Pen torch, distance, symmetry, position E.g.: if one reflex is nasally positioned then the eye is turned outward..

Corneal Reflex

4- Cover test: distance & near .. cover one eye & look for movement of the other eye to take up fixation. 5- Ocular movements: should be tested in different directions of gaze.. 6- Cycloplegic Refraction 7- Dilated Fundus Examination

Cover Test

Treatment: 1- Full cycloplegic correction of refractive errors. 2- Treatment of Amblyopia (vision ↓ but no apparent ocular pathology) .. By occlusion of the “Good” eye 3- Surgery frequently needed to restore alignment & achieve binocular vision. * Strengthening & Weakening procedures of the extraocular muscles E.g.: Esotropia:  MR. Recession, LR. Resection

Amblyopia Definition: •Loss of the visual acuity, •in one or both eyes, •without identifiable organic lesion of the visual pathways, •occurring during the critical period of early visual development..

Aetiology: 1- Stimulus Deprivation: lesion obstructing the visual axis, e.g.: congenital cataract, ptosis, corneal opacity, vitreous hemorrhage, padding.. 2- Strabismus.. 3- Anisometropic (asymmetry of refractive error) – the more hypermetropic eye (or the least myopic) 4- Refractive: high degree of refractive error may result in bilateral amblyopia The younger the age  1- Amblyopia easier to occur 2- Amblyopia is more dense 3- Amblyopia is easier to reverse (treat)

Pathology: Few human data Atrophy of cells in LGN and visual cortex serving the amblyopic eye.. These changes may be partially or wholly reversed if the amblyopia is successfully treated..

Early discovery is important Diagnosis: Early discovery is important Chance of successful management is much reduced after age 6-9 years Child objects occlusion of one eye but not the other Crowding Phenomenon: VA is better when the test letter is presented singly rather than in row with other letters. Neutral density filter: when put in front the normal eye, the VA is reduced, but if put in front of amblyopic eye, VA is either unchanged or even slightly improves..

Rule out any organic lesion e.g.: Macular scar. Management: Rule out any organic lesion e.g.: Macular scar. Define the underlining cause and correct it, e.g.: removal of cataract, full correction of refractive error Patching of the sound eye Usually part time (few hours a day) Duration depends on age, 1week/1year age 6 years old child  6 weeks Beware of inducing amblyopia to the sound eye.. Alternative to patching: a. Density filters b. Atropine eye drops c. Incomplete or no correction of refractive error of the better eyes..

Patching method