Intermittent exotropia

Intermittent exotropia

1. Intermittent Exotropia Dr. Ashraful Huq 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 Outward drifting of either eye Interspersed with periods of good alignment Fig: Intermittent Exotropia

4. Most common form of divergent strabismus Onset before 5 years of age Manifest during – Visual inattention Fatigue Illness Daydreaming Drowsiness upon awakening

5. Causes Imbalance between active convergence and divergence Abnormal orbital anatomy Abnormalities of extraocular muscle proprioception

6. Symptoms Asymptomatic Transient diplopia Asthenopic symptoms Reflex closure of one eye in bright sunlight

7. Evaluation History Visual acuity Measurement of deviation Ocular motility Slit lamp examination Fundoscopy Stereoacuity

8. Cover test in Intermittent Exotropia

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. Revised Newcastle Control Score Home control (XT or monocular eye closure seen) 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) Immediate realignment after dissociation 1 Realignment with aid of blink or re-fixation 2 Remains m anifest after dissociation/prolonged fixation 3 Manifest spontaneously NCS total : n/9

11. Classification Basic : Same at 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 Spectacle Correction Overcorrecting minus lens therapy Part-time patching of dominant eye Active orthoptic treatment Base-in prisms

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. 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 of dominant 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-in prism 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 lateral rectus recession Unilateral lateral rectus recession with ipsilateral medial rectus resection Unilateral lateral rectus recession

22. Fig: (A) Intermittent Exotropia 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 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. 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. Post-operative complication Under Correction : 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