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Intermittent exotropia
Intermittent exotropia is the most common form of divergent strabismus where one or both eyes drift outward intermittently from normal alignment. It typically onset before age 5 and manifests during periods of inattention, fatigue, or drowsiness. Treatment options include non-surgical methods like spectacle correction, patching the dominant eye, or base-in prisms, as well as surgical recession of the lateral rectus muscles to improve alignment if control is lost. The goal of treatment is to restore proper eye alignment and preserve binocular single vision.
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Intermittent exotropia
- 1. Intermittent Exotropia Dr. AshrafulHuq FCPS Consultant Bangladesh Eye Trust Hospital Dhaka, Bangladesh
- 2. Exotropia Constant Exotropia •Infantile Exotropia • Sensory Exotropia • Consecutive Exotropia Intermittent Exotropia Fig: Exotropia of Left eye
- 3. Intermittent Exotropia • Outwarddrifting of either eye • Interspersed with periods of good alignment Fig: Intermittent Exotropia
- 4. Most commonform of divergent strabismus Onset before 5 years of age Manifest during – • Visual inattention • Fatigue • Illness • Daydreaming • Drowsiness upon awakening
- 5. Causes Imbalance betweenactive convergence and divergence Abnormal orbital anatomy Abnormalities of extraocular muscle proprioception
- 6. Symptoms Asymptomatic Transientdiplopia Asthenopic symptoms Reflex closure of one eye in bright sunlight
- 7. Evaluation History Visualacuity Measurement of deviation Ocular motility Slit lamp examination Fundoscopy Stereoacuity
- 8. Cover test inIntermittent Exotropia
- 9. Assessing the control Categoryof 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. Revised Newcastle ControlScore 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. Classification Basic : Sameat near and distant fixation Convergence insufficiency : • Greater at near than at distance • Effects older children and adults
- 12. Divergence excess: Greater at distance fixation than at near Types- • Simulated divergence excess • True divergence excess
- 13. Treatment Two types- •Non-surgical • Surgical
- 14. Non-surgical Treatment SpectacleCorrection Overcorrecting minus lens therapy Part-time patching of dominant eye Active orthoptic treatment Base-in prisms
- 15. Spectacle correction ofrefractive error • Correction of significant myopia, astigmatism and hypermetropia • Correction of mild myopia • Mild to moderate degrees of hypermetropia not routinely corrected
- 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. Part-time patching ofdominant eye • Converts intermittent exotropia to phoria • Done 4 – 6 hours/day • Advantage – Delays surgical intervention • Disadvantage - Prevents fusion & accelerate progression
- 18. Active orthoptic treatments •Consist of antisuppression therapy • Fusional convergence training • Should be used as supplement to surgery
- 19. Prism therapy • Base-inprism used • Promotes bifoveal stimulation • Disadvantage – Causes reduction in fusional vergence amplitude
- 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. Surgery • Bilateral lateralrectus recession • Unilateral lateral rectus recession with ipsilateral medial rectus resection • Unilateral lateral rectus recession
- 22. Fig: (A) IntermittentExotropia before surgery (B) 3 months after surgery
- 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. LR recession andMR 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. Post-operative complications OverCorrection : Persistant esotropia 3-4 weeks after surgery Treatment - • Correction of refractive error • Part-time alternate patching • Base-out prisms • Botulinum toxin injection • Reoperation
- 26. Post-operative complication UnderCorrection : • Observation • Orthoptic exercise • Prism therapy • Reoperation
- 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