Intermittent exotropia

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Intermittent exotropia

  1. 1. Intermittent Exotropia: The Nuts and Bolts Enayatollah Osroosh, student of Msc, Mashhad University
  2. 2. ACKNOWLEDGEMENT Susan A, Cotter, OD, MS for use of data slides.
  3. 3.  Most common form of XT  Onset: typically first few years of life  Most common symptoms • Cosmesis • Blur • Astenopia • Diplopia • Monocular eye closure in bright sunlight • None (suppression/ARC)
  4. 4. IXT: Clinical Characteristics Intermittent fusion Amblyopia is rare Good stereoacuity at near, generally When tropic, 1 of following: • Diplopia • Suppression • Anomalous correspondence
  5. 5.  Divergence excess • Far > near angle: high AC/A • True vs. psuedo (simulated)  Basic • Near = far angle; normal AC/A  Convergence insufficiency • Near > far angle; low AC/A
  6. 6. Follow/Treat How can we tell if a patient is getting worse or better? Determine magnitude under dissociated conditions? Or frequency ? • Ask parents • In-office cover test findings Problems with both
  7. 7. Control Score DescriptionControl Score Observed during 2 30-sec periods, first distance ,then near Constant XT during a 30-sec observation period (before dissociation) 5 XT > 50% of the time during a 30-sec observation period(before dissociation) 4 XT < 50% of the time during a 30-sec observation period(before dissociation) 3 Worst of 3 consecutive trials of covering 1 eye for 10 sec at both distance and near No XT unless dissociated(10 sec):recovery in >5 sec 2 No XT unless dissociated(10 sec):recovery in 1-5 sec 1 Pure phoria: < 1 sec recovery after 10-sec dissociation 0
  8. 8.  Prior to dissociation, observe for 30 seconds: • Constant XT= Grade 5 • XT > 50% =Grade 4 • XT < 50% = Grade 3  Score distance and near fixation separately  If Not spontaneously Tropic…. Move to standard dissociation phase of testing to time “ recovery”
  9. 9. 1..2..3..4..5..6..7..8..9..10..11..12..13..14..15..16..17..18..19..20.. 21..22..23..24..25..26..27..28..29..30.. XT For 10 of 30Sec (33% of 30 Sec) <50% control score=3
  10. 10. 1..2..3..4..5..6..7..8..9..10..11..12..13..14..15..16..17..18..19..20.. 21..22..23..24..25..26..27..28..29..30.. Step2:repeat 30 second observation before dissociation at near
  11. 11. 1-2-3-4-5-6-7-8-9-10 1-2-3 4 Second 1-2-3-4-5-6-7-8-9-10 1-2-3-4-5… 6Second score1 score2
  12. 12. Intraday Variability  Examined 4 times over 1 day  8:00-10:30 / 10:31-13:00 / 13:01-15:30 / 15:31-18:00  Control assessed using control score scale  Variable  stable
  13. 13. Summary: Intraday Study of IXT Control  Control varied over 1 day in many patients  Worst control not always at the end of clinical day
  14. 14.  Alternate cover test-dose not assess “control”  Control-problem of “sampling”- one assessment is not enough  Distance stereoacuity –need multiple measures  Near stereoacuity – often “good” anyways
  15. 15. IXT: Other Diagnostic Evaluation Consideration  Cycloplegic refraction  Cover test at remote distance  Sensorimotor evaluation  Distance Randot stereo test  Worth 4 –dot when tropia is manifest  Hering-Bielschowsky Afterimage Test when tropia manifest?
  16. 16.  Monitor  Refractive correction  Occlusion  Over-minus lens  Prism  Vision Therapy  Surgery
  17. 17.  uncorrected ametropia?  equally accommodative accuracy  Discourage suppression  Promote sensory fusion  Moderate/high hyperopia consideration?
  18. 18.  IXT > 25-30 pd ???.... High recurrence rate  post-surgical ET and loss of stereopsis  Poor agreement on type of surgery
  19. 19.  Uses feedback techniques/procedures to improve fusional vergence & sensory fusion  Goal is not to decrease magnitude, but to decrease frequency and increase “control” Active Vision Therapy
  20. 20. Phase 1: optical correction Phase 2: monocular function Phase 3: improve Sensory fusion
  21. 21.  Gross convergence  Fusional vergence  Anti-suppression therapy, including diplopia awareness when XT
  22. 22.  Convergence surprise  Pencil push up  Brock string  3.dot card  Goal: Voluntary Convergence
  23. 23.  accommodation control Smooth fusional vergence
  24. 24. Step fusional vergence
  25. 25. 3 to 2 to 1
  26. 26.  During active therapy with suppression check  Can use filters for passive TV watching
  27. 27.  Pathological diplopia  Use Red & Green filter in a dark room Flash light, Penlight, Candle  Prism insertion/removal

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