Exodeviation

Exodeviation

1. EXODEVIATION Shahana Nethradhama school of optometry

2. Introduction Exodeviation is also known as divergent strabismus Visual axes that form a divergent angle as they proceed outward constitute an exodeviation. Diverged visual axes kept latent by single binocular vision constitute exophoria;when manifest,the misaligned visual axes constitute exotropia.

3. Classification Exodeviation are classified into two types: Concomitant 2. Incomitant a)Primary a)paralytic Infantile exotropia b)Restrictive Intermittent exotropia c)musculofascial innervational anomalies b)secondary Sensory exotropia Consecutive exotropia

4. Primary Exotropia 1)Infantile exotropia: A divergent strabismus that begins during the first 6 months of life is classified as infantile exotropia It is less common than ifantile esotropia It is a rare condition In infants some cases of constant exotropia maybe associated with craniofacial syndromes and structural abnormalities in the eye. Patient who have albinism,cerebral palsy can also cause exotropia. Signs and symptoms: Large angle of deviation more than 35prism dioptre Amblyopia Poor fusional capacity OKN and monocular nasotemporal pursuit asymmetry

5. Treatment Treatment often includes surgery because of the large angle of constant exotropia. Prisms are usually not helpful in cases with poor fusion potential. Surgery should be considered after 1) the refractive error and fundus have been assessed,2)Amblyopia has been treated 3)the angle of exotropia is stable on subsequent examinations,and 4)other treatment optionsare not appropriate or have failed.

6. 2)Intermittent exotropia: In intermittent exotropia the patient sometimes manifests diplopia,suppression or anomalous retinal correspondence and at other times binocular alignment with good stereopsis. Signs and Symptoms: Blurring of vision Minimal or no amblyopia Level of stereopsis equal to or greater than 60 seconds of arc when fusing Discomfort Diplopia Treatment: Therapy for intermittent exotropia should include correction of significant refractive error. Prism therapy is often used in conjunction with active vision therapy

7. Secondary exotropia 1)Sensory exotropia: A divergent strabismus resulting from a unilateral decrease in vision that disrupts fusion,sensory exotropia may be due to a sensory deficit such as uncorrected anisometropia,unilateral cataract, or other unilateral visual impairment Sensory exotropia occurs in less than 3% of all strabismic children Signs and symptoms: Constant unilateral exotropia at distance and near High degrees of anisometropia, which can be causative Functional amblyopia Reduced binocular vision and high level stereopsis in patients with early childhood onset. Treatment: Treat the cause

8. 2)Consecutive exotropia: Exotropia that occurs following surgical or optical correction of an esotropia is referred to as consecutive exotropia This form of exotropia can also occur spontaneously in a formely essotropic patients. Signs and Symptoms: Constant unilateral exotropia at distance and near Hyperopia greater than 4.50D Diplopia High level of stereopsis Treatment: Consecutive exotropia that is spontaneous and optically induced can be treated by reducing the power of the hyperopic lenses

9. Duane classification There are 5 types: Basic exodeviation: The distance deviation is approximately equal to the near deviation. Divergence excess: The exodeviation is at least 10 to 15 prism dioptre more at distance than at near Stimulated divergence excess: The exodeviation appears to be greater at distance than at near but after patch test the fusion is disrupted and the measurements are repeated the near deviation amount approaches the distance deviation Convergence insufficiency: The near deviation is larger than the distance deviation by 10-15prism dipter Consecutive exodeviation: Surgical overcorrection of esotropia

10. Measuring the angle of deviation Patch test:- The patch test is used to control the tonic fusional convergence to differentiate pseudodivergence excess from true divergence excess and to reduce the angle variability Contrary to the early practice of patching one eye for 24 hrs it is now found the eye for 30 min is sufficient to suspend the tonic fusional convergence and thus reveal the actual amount of deviation.

11. +3D near add test (lens gradient method ):- This test has been devised to diagnose the patients of divergence excess due to high AC/A ratio. This test uses the lens gradient method to measure the AC/A ratio These patients are the ones who will continue to have a distance near disparity post operatively and may require bifocal spectacles after surgery for a consecutive esotropia at near This test should be resorted to in patients who have a distance deviation greater than near deviation of 10 prism dioptre or more after the patch test This test is based upon the principle of suspension of accommodation and accommodative convergence.

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