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Exodeviations

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  • 1. EXODEVIATIONSDr Abida Fasahtay
  • 2. EXODEVIATION• EXO-Visual axis is deviated laterallyFovea rotated nasallyEXODEVIATION = DIVERGENT STRABISMUSLatent(controlled by fusion)Manifest:-Intermittent or constant-Unilateral or alternating
  • 3. PSEUDOEXOTROPIA• Appearance of exodeviationWide interpupillary distanceLarge positive angle kappa- hypermetropia, retinopathy ofprematurity, toxocara canis retinitis.
  • 4. TYPESA. Concomitant1. Primary• Infantile exotropia• Intermittent exotropia2. Secondary• Sensory exotropia• Consecutive exotropiaB. Incomitant1. Paralytic2. Restrictive3. Musculofascial innervational anomalies
  • 5. ETIOLOGY• Exact etiology unknown• Proposed causes:Excessive tonic divergenceAnatomical and mechanical factors within the orbit
  • 6. MAGICIAN’S FORCEPSPHENOMENON• Abnormal proprioceptive impulsesoriginating from the dominant eyeas a cause of exodeviation asconcluded by Mitsui• But unlikely that a mechanismother than a visually elicited fixationreflex accounts for thephenomenon
  • 7. 1. DUANE’S CLASSIFICATION• Merely a descriptive classification1. Divergence excess pattern2. Basic exodeviation3. Convergence insufficiency pattern4. Simulated divergence excess patternDifference of atleast 15 prism diopters
  • 8. 2. CLASSIFICATION ON THE BASIS OFUNDERLYING FUSIONAL RESERVE1.Exophoria : XP2.Intermittent exotropia : X(T)3.Manifest exotropia : XT
  • 9. PRIMARY EXODEVIATIONSCLINICAL 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. PROGRESSION1. Divergence excess pattern → Stable2. Basic exodeviation → Increased deviation or secondaryconvergence insufficiency3. Convergence insufficiency pattern→ binocular functiondegenerates rapidly4. Simulated divergence excess pattern → Increased neardeviation
  • 11. SIGNS AND SYMPTOMS• EXOPHORIA:EyestrainHeadacheBlurring of visionDifficulties with prolonged periods of readingDiplopia• CHILDREN WITH INTERMITTENT OR CONSTANTEXOTROPIA:Less frequently symptomatic• ADULTS WITH INTERMITTENT EXOTROPIA:Commonly symptomatic
  • 12. PHOTOPHOBIA• Common in intermittent exodeviationsChild is outdoors & looking at infinityNo stimulus for convergenceBright sunlight dazzles the retinasDisruption of fusionDeviation becomes manifestDiplopia and confusionChild closes one eye
  • 13. MICROPSIA• Less well known symptom• Occurs when patient uses accomodative convergence tocontrol exodeviation at distance
  • 14. SPECIAL TESTS : POST OCCLUSIONTEST OF SCOBEE-BURAINDIVERGENCEEXCESSNEARDEVIATIONAFTERUNILATERALOCCLUSIONTRUE LITTLEINFULENCESIMULATED INCREASE
  • 15. SPECIAL TESTS : +3.00D SPHERICALLENS TEST• +3.00D spherical lenses suspend accommodation andthus accommodative convergenceEXOTROPIA NEAR DEVIATION USING+3.00D LENSLOW AC/A RATIO LITTLE INFLUENCEHIGH AC/A RATIO INCREASE
  • 16. MEASUREMENTS OF THE DEVIATION• Unless the target used for distance fixation forces patientsto relax accommodation, and with it convergence, truedeviation of the eyes at distance fixation may remainconcealed.• Therefore, measure angle while patient reads the 6/9 lineon 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 constantexodeviations : Usually SurgeryHowever, nonsurgical measures may be indicated tocreate optimal sensory conditions before surgery
  • 19. NONSURGICAL TREATMENTSPECTACLE CORRECTION :• Astigmatism and anisometropia : corrected• Myopia : fully corrected• Hypermetropia : correction depends upon its degree andpatient ageAs a rule, a hypermetropia of less than +2.00DS inchildren : do not correct• Presbyopia : correct any underlying hypermetropia ,weakest bifocal lens, base in prisms for near vision
  • 20. NONSURGICAL TREATMENTUSE OF MINUS LENSES :• High AC/A ratio : minus lenses• Convergence insufficiency pattern : minus lensesprescribed as lower segment bifocals• Divergence excess pattern : minus lenses prescribed asupper segment bifocalsPRISMS :• 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 nohistory of intermittency↓Surgery performed as soon as reliable and constantmeasures 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 periodof intermittencyObservation-Occasional manifest squint-Asymptomatic-No progressionNo Surgery-Manifest squint ˃ 50% of waking hours-Asthenopic symptoms-ProgressionSurgery
  • 24. The most desirable age at which surgery should be performed forintermittent exodeviations has been a matter of some disputeMajority advocate delaying surgery until the child hasreached at least 4 years of age.Rapid functional deterioration offusional control inspite ofnonsurgical RxSurgery at anearlier age shouldbe considered
  • 25. Finally, the size of deviation determines the decision to operateFUNCTIONAL POINT OF VIEW Atleast 15 prism diopterCOSMETIC 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 torevert to their former position2. Postoperative diplopia → fusional vergences → Stabilizeeventual alignment of eyes• Lesser degrees of overcorrection → recurrence ofexodeviation• Higher degrees of overcorrection → necessitate furthersurgery for consecutive esotropia
  • 27. CHOICE OF PROCEDURETRUE DIVERGENCE EXCESS B/L lateral rectus recessionSIMULATED DIVERGENCE EXCESSOR BASIC EXOTROPIAU/L recession-resection of lateral andmedial recti of nondominant eyeCONVERGENCE INSUFFICIENCY B/L medial rectus resectionRecession of lateral rectus muscle is more effective inreducing the deviation at distance fixation than thedeviation at near
  • 28. SURGICALRECESSION OF LATERAL RECTUS MUSCLESURGICAL RESECTION OF MEDIAL RECTUS MUSCLE3-6 mm depending upon the size of deviation
  • 29. MANAGEMENTOF OVERCORRECTIONS:(CONSECUTIVE ESOTROPIA)1. Large ovecorrection with gross limitation of ocularmotilityImmediate Surgery2. Small overcorrectionComitant IncomitantMioticsPlus lensesPrismSurgerySurgeryMANAGEMENT OF UNDERCORRECTIONS:Usually surgery
  • 30. SECONDARY EXODEVIATIONSSENSORY EXOTROPIA• Primary sensory deficit in one eye:AnisometropiaCornea opacitiesDense cataractAphakiaOptic atrophyCentral macular scars etcDisruption of fusion• Correction of the visual deficit if possible• Surgical correction : cosmetic
  • 31. SECONDARY EXODEVIATIONSCONSECUTIVE EXOTROPIA• Formerly esotropic patient• Either spontaneously or after surgical overcorrection• Treatment : Surgery ( cosmetic )
  • 32. INCOMITANT STRABISMUSPARALYTIC• 3rd nerve palsy• Internuclear ophthalmoplegia (INO)• Ocular myastheniaRight INORight 3rd nerve palsy Ocular Myasthenia
  • 33. INCOMITANT STRABISMUSRESTRICTIVE• 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 asadduction• Abduction:- normal• Adduction:-limited-globe retraction-narrowing of palpebral aperture-upshoot or downshootINCOMITANT STRABISMUSMUSCULOFASCIAL INNERVATIONAL ANOMALIES
  • 35.  Duanes’s retraction syndrome type 2 :• Treatment:- Results of surgery disappointing- Indication : significant deviation in primary position orintolerable anomalous head position- Ipsilateral recession of lateral rectus muscle
  • 36. CONVERGENCE INSUFFICIENCY• Remote near point of convergence and poor near fusionalvergence 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 surgicalcorrectionDeviation inprism diopterRecess LRBoth eyemmResect MRBoth eyemmRecess LR + Resect MROne eyemm15 4.5 3.0 4.0 3.020 5.0 3.5 5.0 3.525 5.5 4.0 5.5 4.030 6.0 4.5 6.0 4.035 6.5 5.0 6.5. 4.540 7.0 5.5 7.0 5.050 7.5 6.0 7.5 5.5

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