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Intermittent exotropia

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Intermittent exotropia

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Intermittent exotropia

  1. 1. Intermittent Exotropia Dr. Ashraful Huq FCPS Consultant Bangladesh Eye Trust Hospital Dhaka, Bangladesh
  2. 2. Exotropia  Constant Exotropia • Infantile Exotropia • Sensory Exotropia • Consecutive Exotropia  Intermittent Exotropia Fig: Exotropia of Left eye
  3. 3. Intermittent Exotropia • Outward drifting of either eye • Interspersed with periods of good alignment Fig: Intermittent Exotropia
  4. 4.  Most common form of divergent strabismus  Onset before 5 years of age  Manifest during – • Visual inattention • Fatigue • Illness • Daydreaming • Drowsiness upon awakening
  5. 5. Causes  Imbalance between active convergence and divergence  Abnormal orbital anatomy  Abnormalities of extraocular muscle proprioception
  6. 6. Symptoms  Asymptomatic  Transient diplopia  Asthenopic symptoms  Reflex closure of one eye in bright sunlight
  7. 7. Evaluation  History  Visual acuity  Measurement of deviation  Ocular motility  Slit lamp examination  Fundoscopy  Stereoacuity
  8. 8. Cover test in Intermittent Exotropia
  9. 9. Assessing the control Category of control of exodeviation Manifestation of Exodeviation Fusion resumes Good control After Cover test Rapidly without blinking /refixating Fair control After Cover test After blinking /refixating Poor control Spontaneously Remain manifest
  10. 10. Revised Newcastle Control Score Home control (XT or monocular eye closure seen) 0 Never 1 <50% of time fixing in distance 2 >50% of time fixing in distance 3 >50% of time fixing in distance + seen at near Clinic control (scored for near and distance fixation) 0 Immediate realignment after dissociation 1 Realignment with aid of blink or re-fixation 2 Remains manifest after dissociation/prolonged fixation 3 Manifest spontaneously NCS total : n/9
  11. 11. Classification  Basic : Same at near and distant fixation  Convergence insufficiency : • Greater at near than at distance • Effects older children and adults
  12. 12.  Divergence excess : Greater at distance fixation than at near Types- • Simulated divergence excess • True divergence excess
  13. 13. Treatment  Two types- • Non-surgical • Surgical
  14. 14. Non-surgical Treatment  Spectacle Correction  Overcorrecting minus lens therapy  Part-time patching of dominant eye  Active orthoptic treatment  Base-in prisms
  15. 15. Spectacle correction of refractive error • Correction of significant myopia, astigmatism and hypermetropia • Correction of mild myopia • Mild to moderate degrees of hypermetropia not routinely corrected
  16. 16. Overcorrecting minus lens therapy • Stimulates accommodative convergence & control exodeviation • Usually 2-4 D beyond refractive error correction • Advantage – Promotes fusion & delay surgery • Disadvantage – Asthenopia
  17. 17. Part-time patching of dominant eye • Converts intermittent exotropia to phoria • Done 4 – 6 hours/day • Advantage – Delays surgical intervention • Disadvantage - Prevents fusion & accelerate progression
  18. 18. Active orthoptic treatments • Consist of antisuppression therapy • Fusional convergence training • Should be used as supplement to surgery
  19. 19. Prism therapy • Base-in prism used • Promotes bifoveal stimulation • Disadvantage – Causes reduction in fusional vergence amplitude
  20. 20. Indications of Surgical Treatment • Gradual loss of fusional control • Increased frequency of manifest phase • Increase size of the basic deviation • Development of suppression • Decrease of Stereoacuity
  21. 21. Surgery • Bilateral lateral rectus recession • Unilateral lateral rectus recession with ipsilateral medial rectus resection • Unilateral lateral rectus recession
  22. 22. Fig: (A) Intermittent Exotropia before surgery (B) 3 months after surgery
  23. 23. Lateral rectus recession Exotropia (PD) LR recession(mm each eye) 20 4.5 25 5.0 30 6.0 35 6.5 40 7.0 45 7.5 50 8.0
  24. 24. LR recession and MR resection Exotropia (PD) LR recession (mm) MR resection (mm) 20 4.0 3.0 25 5.0 4.0 30 5.5 4.0 35 6.5 4.5 40 7.0 4.5 50 8.0 4.5
  25. 25. Post-operative complications  Over Correction :  Persistant esotropia 3-4 weeks after surgery  Treatment - • Correction of refractive error • Part-time alternate patching • Base-out prisms • Botulinum toxin injection • Reoperation
  26. 26. Post-operative complication  Under Correction : • Observation • Orthoptic exercise • Prism therapy • Reoperation
  27. 27. Take Home Message • Intermittent Exotropia is difficult to diagnose • Proper evaluation required • Timely treatment necessary • Follow-up must be done to record progression • Goal is to restore alignment and preserve Binocular Single Vision

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