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)
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 :
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