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Comitant strabismus.ophthalmology.squint.pptx

Comitant strabismus is a type of squint where the deviation of the eye remains constant in all gaze directions, with non-limited ocular movement. It includes conditions like esotropia and exotropia, with various clinical features and treatment options such as glasses, amblyopia therapy, and surgery. Evaluation involves a detailed history and examination to assess the degree of deviation and associated factors for an accurate diagnosis and management plan.

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Comitant strabismus PRATHEEK J
• Type of manifest squint in which amount of deviation in the squinting eye remains constant in all directions of gaze; and there is no limitation of ocular movements
Etiology • Sensory obstacles – hinder the formation of a clear image in one eye include • Refractive errors • Prolonged use of incorrect spectacles • Anisometropia • Corneal and lenticular opacities • Diseases of macula • Optic atrophy
• Motor obstacles – hinder maintenance of two eyes in correct positional relationship in primary gaze and during different ocular movements, such factors are – • Congenital abbormalities of shape and size of orbit • Abnormalities of extraocular muscles • Abnormal accomodative convergence per accomodative ratio (AC/A) ratio • Cental obstacles – deficient development of fusion faculty
Clinical features of comitant strabismus 1. Ocular deviation. Characteristics are: Unilateral or alternating. Inward deviation (esotropia) or outward deviation (exotropia) or vertical deviation (hypertropia). Primary deviation (of squinting eye) is equal to secondary deviation (deviation of normal eye under cover when patient fixes with squinting eye). • Ocular deviation is equal in all the directions of gaze.
2. Ocular movements are not limited in any direction. 3. Refractive error may or may not be associated. 4. Suppression and amblyopia may develop as sensory adaptation to strabismus. Suppression may be monocular (in monocular squint)and alternating (in alternating strabismus)Amblyopia develops in long standing monocular strabismus only and is responsible for poor visual acuity. • 5. A-V patterns may be observed in horizontal strabismus
Types of comitant strabismus • Convergent squint {esoteopia} • Divergent squint (exotropia) • Vertical squint [hypertropia]
Convergent squint / Comitant esotropia • Inward deviation of one eye • Most common in children • Can be unilateral or alternating (other eye takes up fixation) • Clinico-etiological types • Infantile • Accomodative • Essential acquired • Other onset non accomodative • Sensory • Consecutive
Infantile esotropia • Onset – 2 to 4 months • Usually alternate • Angle of deviation is constant and fairly large (>35°) • Binocular vision doesn’t develop and there is alternate fixation in primary gaze and cross fixation in lateral gaze • Amblyopia in 25% to 40% • Associations like inferior oblique overaction, dissociated vertical deviation • Surgery is the treatment of choice – Amblyopia : patch normal eye Recession of both medial recti, done between 6 months to 2 years
Accomodative esotropia • Most common in children • Around 2 to 3 years • Pathogenesis • If due to some reason excessive accomodation is required to focus at the near object; there will be associated excessive convergence as well causing accomodative esotropia • Types • Refractive • Non refractive • Mixed
Refractive accomodative esotropia • Pathogenesis • It is associated with high hypermetropia (+4 to +7D). Esotropia develops due to associated excessive convergence. • Clinical features • Age of onset: 2-3 years • AC/A ratio is normal • Esotropia is both for near as well as distance, may be slightly more for near than distance; and is fully correctable by the use of spectacles • Treatment • Full correction of hypermetropia, after cycloplegic refraction is the treatment of choice
Non refractive • Pathogenesis • In this condition AC/A ratio is abnormally high. • Clinical features include: • Age of onset is 2-3 years • AC/A ratio is abnormally high • Refractive error, may or may not be present. • Esotropia is typically greater for near than distance (minimal or no deviation for distance) • Treatment consists of decreasing the demand for accommodation by: • Bifocal glasses with +3D add for near vision, corrects the esotropia • Miotics facilitate accommodation by contracting ciliary muscles and this reduce the associated accommodative convergence
Mixed • Pathogenesis. • It occurs partially due to hypermetropia and partially there in non- accommodative element. • Clinical features include: • Age of onset: 2-3 years • Hypermetropia is present • AC/A ratio is usually normal • Esotropia is both for near and distance. • Treatment consists of: • Full hypermetropic correction usually corrects the esotropia partially (accommodative part) both for near and distance. • Surgical treatment is required for the residual esotropia(non- accommodative part).
Other acquired non- accomodative esotropias This group includes all those acquired primary esodeviations in which amount of deviation is not affected by the state of accommodation. It includes: • Acute concomitant esotropia, • Cyclic esotropia, • Nystagmus blockage syndrome, • Esotropia in myopia and microtropia.
• Sensory esotropia • It results from monocular lesions (in childhood) which either prevent the development of normal binocular vision or interfere with its maintenance. Examples of such lesions are:cataract, severe congenital ptosis, aphakia, anisometropia,optic atrophy, retinoblastoma, central chorioretinits, and so on. • • Consecutive esotropia • It results from surgical overcorrection of exotropia.
Divergent squint (Exotropia) • It is characterized by outward deviation of one eye while other eye fixates. It’s clinico- etiological types are 1. Congenital 2. Primary 3. Sensory 4. Consecutive
Congenital exotropia • Age of onset. It is rare usually present at birth and almostalways presents before six months of age. • Occular deviation. It is characterised by a fairly large and constant angle of squint, usually alternate with homonymous fixation in lateral gaze. • Amblyopia is seen in a minority of cases (from 0 to 25%). • Both DVD and IOOA may be associated with infantile exotropia.
Primary exotropia • It may be unilateral or alternating and may present as intermittent or constant exotropia. • Intermittent exotropia. It is the most common type of exodeviation with following features: • Age of onset is usually early between 2 to 5 years. • Deviation becomes manifest at times and latent at others. Precipitating factors include bright light, fatigue, ill health and day dreaming.
• Constant exotropia. • If not treated in time the intermittent exotropia may decompensate to become constant exotropia • Types. Primary exotropia may be of following three types: • Convergence insufficiency type of exotropia is greater fornear than distance, • Divergence excess type of exotropia is greater for distancethan near, or • Basic non-specific type exotropia is equal for near anddistance
Sensory exotropia It is a constant unilateral deviation which results from longstanding monocular lesions (in adults), associated with low vision in the affected eye. Common causes include: traumatic cataract, corneal opacity,optic atrophy, anisometropic amblyopia, retinal detachment and organic macular lesions. Consecutive exotropia • It is a constant unilateral exotropia which results either due to surgical overcorrection of esotropia, or rarely due to spontaneous conversion of small degree esotropia with amblyopia into exotropia.
Evaluation of a case of comitant strabismus • History • Include Onset, duration, progression, any illness, intermittent or constant, unilateral or alternating, H/O diplopia, family history, H/O head tilt / turn • Examination • Inspection – convergent or divergent • Ocular movements – U/L & B/L • Pupillary reaction – abnormal in sensory exotropia • Media and fundus – may reveal associated disease of ocular media, retina, optic nerve • Testing of vision and refractive error • Cover tests
Cover tests Direct cover test – confirms presence of manifest squint Patient is asked to fixate on point light, then normal eye is covered while observing movement of uncovered eye – in squint it moves in opposite direction. It can be performed for both near and distance fixation Cover-uncover test – one eye covered with occluder and other is made to fixate on object, in the presence of phoria the eye under cover will deviate, the direction of movement of eye on removing the cover tells type of heterotropia (eyes moves inwards in exophoria and outwards in esophoria) Alternate cover test – Reveal wheter squint is U/L or alternate and differentiates comitant squint from paralytic squint
• Estimation of angle of deviation • Hirschberg corneal reflex test • The prism and cover test – tell amount of deviation inprism diopters, measure hetrotropia and heterophoria • Modified Krimsky corneal reflex test • Measurement of deviation with synoptophore • Tests for grade of binocular vision and sensory functions • Normal binocular single vision consist 3 grades • Few tests for sensory functions are
Worth’s four-dot test A.Normal – sees all four lights B.Abnormal retinal correspondence C.Left suppression D.Right supression E.Diplopia
Tests for fixation • Tested with visuoscope / fixation star of opthalmoscope • Patient is asked to cover one eye and fix the star with other eye (centric on fovea / eccentric)
After-image test Right fovea stimulated with vertical and left with horizontal bright light and patient is asked to draw position of after images A. Normal B. Esotropic patient with ARC (Abnormal retinal correspondence) C. Exotropia with ARC
Sensory function tests with synoptophore • It consists two tubes, having right angled bend, mounted on a base Tests include • Estimation of grades of binocular vision • Detection of normal / abnormal retinal correspondence (ARC)
Treatment modalities 1. Spectacles with full correction of refractive error 2. Occlusion therapy – in presence of amblypia, normal eye is occluded and advised to use squinting eye 3. Preoperative orthoptic exercises after amblypia correction 4. Squint surgery to correct deviation These are to weaken strong muscle by recession and weak muscle by resection (shortening muscle) Type and amount of muscle surgery Roughly 1 mm resection of MR correct 2 PD, MR resection – 8 mm, recession – 7 mm is max. 5. To improve range and maintain binocular vision
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