Exodeviations
- 2. EXODEVIATION • EXO- Visual axis is deviated laterally Fovea rotated nasally EXODEVIATION = DIVERGENT STRABISMUS Latent (controlled by fusion) Manifest: -Intermittent or constant -Unilateral or alternating
- 3. PSEUDOEXOTROPIA • Appearance of exodeviation Wide interpupillary distance Large positive angle kappa- hypermetropia, retinopathy of prematurity, toxocara canis retinitis.
- 4. TYPES A. Concomitant 1. Primary • Infantile exotropia • Intermittent exotropia 2. Secondary • Sensory exotropia • Consecutive exotropia B. Incomitant 1. Paralytic 2. Restrictive 3. Musculofascial innervational anomalies
- 5. ETIOLOGY • Exact etiology unknown • Proposed causes: Excessive tonic divergence Anatomical and mechanical factors within the orbit
- 6. MAGICIAN’S FORCEPS PHENOMENON • Abnormal proprioceptive impulses originating from the dominant eye as a cause of exodeviation as concluded by Mitsui • But unlikely that a mechanism other than a visually elicited fixation reflex accounts for the phenomenon
- 7. 1. DUANE’S CLASSIFICATION • Merely a descriptive classification 1. Divergence excess pattern 2. Basic exodeviation 3. Convergence insufficiency pattern 4. Simulated divergence excess pattern Difference of atleast 15 prism diopters
- 8. 2. CLASSIFICATION ON THE BASIS OF UNDERLYING FUSIONAL RESERVE 1.Exophoria : XP 2.Intermittent exotropia : X(T) 3.Manifest exotropia : XT
- 9. PRIMARY EXODEVIATIONS CLINICAL CHARACTERISTICS • Latent or intermittent form ↑ • Prevalence less than esodeviations • Age of onset of the majority is shortly after birth • Genuine “congenital” exotropia : poor prognosis
- 10. PROGRESSION 1. Divergence excess pattern → Stable 2. Basic exodeviation → Increased deviation or secondary convergence insufficiency 3. Convergence insufficiency pattern→ binocular function degenerates rapidly 4. Simulated divergence excess pattern → Increased near deviation
- 11. SIGNS AND SYMPTOMS • EXOPHORIA: Eyestrain Headache Blurring of vision Difficulties with prolonged periods of reading Diplopia • CHILDREN WITH INTERMITTENT OR CONSTANT EXOTROPIA: Less frequently symptomatic • ADULTS WITH INTERMITTENT EXOTROPIA: Commonly symptomatic
- 12. PHOTOPHOBIA • Common in intermittent exodeviations Child is outdoors & looking at infinity No stimulus for convergence Bright sunlight dazzles the retinas Disruption of fusion Deviation becomes manifest Diplopia and confusion Child closes one eye
- 13. MICROPSIA • Less well known symptom • Occurs when patient uses accomodative convergence to control exodeviation at distance
- 14. SPECIAL TESTS : POST OCCLUSION TEST OF SCOBEE-BURAIN DIVERGENCE EXCESS NEAR DEVIATION AFTER UNILATERAL OCCLUSION TRUE LITTLE INFULENCE SIMULATED INCREASE
- 15. SPECIAL TESTS : +3.00D SPHERICAL LENS TEST • +3.00D spherical lenses suspend accommodation and thus accommodative convergence EXOTROPIA NEAR DEVIATION USING +3.00D LENS LOW AC/A RATIO LITTLE INFLUENCE HIGH AC/A RATIO INCREASE
- 16. MEASUREMENTS OF THE DEVIATION • Unless the target used for distance fixation forces patients to relax accommodation, and with it convergence, true deviation of the eyes at distance fixation may remain concealed. • Therefore, measure angle while patient reads the 6/9 line on the visual acuity chart
- 17. SENSORYADAPTATIONS • Rare • Strabismic amblyopia : almost non-existent • Abnormal retinal correspondence : rarely seen • Alternate suppression : Alternate exotropia
- 18. THERAPY • Exophoria without asthenopia : No Rx • Symptomatic exophoria and intermittent and constant exodeviations : Usually Surgery However, nonsurgical measures may be indicated to create optimal sensory conditions before surgery
- 19. NONSURGICAL TREATMENT SPECTACLE CORRECTION : • Astigmatism and anisometropia : corrected • Myopia : fully corrected • Hypermetropia : correction depends upon its degree and patient age As a rule, a hypermetropia of less than +2.00DS in children : do not correct • Presbyopia : correct any underlying hypermetropia , weakest bifocal lens, base in prisms for near vision
- 20. NONSURGICAL TREATMENT USE OF MINUS LENSES : • High AC/A ratio : minus lenses • Convergence insufficiency pattern : minus lenses prescribed as lower segment bifocals • Divergence excess pattern : minus lenses prescribed as upper segment bifocals PRISMS : • Base in prisms
- 21. NONSURGICAL TREATMENT • ORTHOPTICS : • Supplement to surgery • Convergence exercises and occlusion
- 22. SURGICAL TREATMENT • Manifest exotropia present at or shortly after birth with no history of intermittency ↓ Surgery performed as soon as reliable and constant measures can be obtained • Large angle constant exodeviation in adults ↓ Surgery performed as soon as diagnosis made • Exophoria with asthenopia ↓ Surgery only of deviation not controlled by prisms
- 23. • Intermittent exotropia or constant exotropia preceded by a long period of intermittency Observation -Occasional manifest squint -Asymptomatic -No progression No Surgery -Manifest squint ˃ 50% of waking hours -Asthenopic symptoms -Progression Surgery
- 24. The most desirable age at which surgery should be performed for intermittent exodeviations has been a matter of some dispute Majority advocate delaying surgery until the child has reached at least 4 years of age. Rapid functional deterioration of fusional control inspite of nonsurgical Rx Surgery at an earlier age should be considered
- 25. Finally, the size of deviation determines the decision to operate FUNCTIONAL POINT OF VIEW Atleast 15 prism diopter COSMETIC POINT OF VIEW Atleast 20-25 prism diopter
- 26. GOALS OF SURGERY • For intermittent exotropia, small surgical overcorrection (10-20 prism diopter) is desirable : 1. Divergent strabismic eyes show a strong tendency to revert to their former position 2. Postoperative diplopia → fusional vergences → Stabilize eventual alignment of eyes • Lesser degrees of overcorrection → recurrence of exodeviation • Higher degrees of overcorrection → necessitate further surgery for consecutive esotropia
- 27. CHOICE OF PROCEDURE TRUE DIVERGENCE EXCESS B/L lateral rectus recession SIMULATED DIVERGENCE EXCESS OR BASIC EXOTROPIA U/L recession-resection of lateral and medial recti of nondominant eye CONVERGENCE INSUFFICIENCY B/L medial rectus resection Recession of lateral rectus muscle is more effective in reducing the deviation at distance fixation than the deviation at near
- 28. SURGICALRECESSION OF LATERAL RECTUS MUSCLE SURGICAL RESECTION OF MEDIAL RECTUS MUSCLE 3-6 mm depending upon the size of deviation
- 29. MANAGEMENTOF OVERCORRECTIONS: (CONSECUTIVE ESOTROPIA) 1. Large ovecorrection with gross limitation of ocular motility Immediate Surgery 2. Small overcorrection Comitant Incomitant Miotics Plus lenses Prism Surgery Surgery MANAGEMENT OF UNDERCORRECTIONS: Usually surgery
- 30. SECONDARY EXODEVIATIONS SENSORY EXOTROPIA • Primary sensory deficit in one eye: Anisometropia Cornea opacities Dense cataract Aphakia Optic atrophy Central macular scars etc Disruption of fusion • Correction of the visual deficit if possible • Surgical correction : cosmetic
- 31. SECONDARY EXODEVIATIONS CONSECUTIVE EXOTROPIA • Formerly esotropic patient • Either spontaneously or after surgical overcorrection • Treatment : Surgery ( cosmetic )
- 32. INCOMITANT STRABISMUS PARALYTIC • 3rd nerve palsy • Internuclear ophthalmoplegia (INO) • Ocular myasthenia Right INORight 3rd nerve palsy Ocular Myasthenia
- 33. INCOMITANT STRABISMUS RESTRICTIVE • Dysthyroid orbitomyopathy • Fibrosis secondary to orbital trauma and orbital surgery • Parasitic cyst • Orbital tumors
- 34. Duanes’s retraction syndrome type 2 : • Lateral rectus innervation present on abduction as well as adduction • Abduction: - normal • Adduction: -limited -globe retraction -narrowing of palpebral aperture -upshoot or downshoot INCOMITANT STRABISMUS MUSCULOFASCIAL INNERVATIONAL ANOMALIES
- 35. Duanes’s retraction syndrome type 2 : • Treatment: - Results of surgery disappointing - Indication : significant deviation in primary position or intolerable anomalous head position - Ipsilateral recession of lateral rectus muscle
- 36. CONVERGENCE INSUFFICIENCY • Remote near point of convergence and poor near fusional vergence amplitudes • Older child or adult • Asthenopic symptoms • Exophoria at near but not exotropia • D/D convergence insufficiency type of exotropia • Treatment : - Correction of refraction - Orthoptic exercises - Base out prisms - If these fail, base in prism reading glasses - Medial rectus resection : rare cases
- 37. CONVERGENCE PARALYSIS • Little if any fusional vergence amplitude • Usually secondary to intracranial lesion • Exotropia and diplopia on attempted near fixation only • Adduction and accomodation are normal • Distinct from convergence insufficiency: - Acute onset - Inability to overcome any base out prism • Treatment : - Base in prism at near - Occlusion of one eye at near - Eye muscle surgery is contraindicated
- 38. THANK YOU
- 39. EXOTROPIA : amount of surgical correction Deviation in prism diopter Recess LR Both eye mm Resect MR Both eye mm Recess LR + Resect MR One eye mm 15 4.5 3.0 4.0 3.0 20 5.0 3.5 5.0 3.5 25 5.5 4.0 5.5 4.0 30 6.0 4.5 6.0 4.0 35 6.5 5.0 6.5. 4.5 40 7.0 5.5 7.0 5.0 50 7.5 6.0 7.5 5.5