6 Strabismus
6.10 Consecutive Exotropia
Consecutive exotropia refers to an exotropia that develops following a prior esotropia. It may have features of a paresis (because of underaction of the medial rectus) or restriction (because of tightening / fibrosis of the lateral rectus). Causes include:
- Post-operative following exotropia surgery (infantile or accommodative ET)
- Spontaneous
1. Visual Acuity (Best Corrected)
- Exotropic eye may be amblyopic
2. Spectacles
- BI prism- apex points towards the deviation
3. Inspection
- Abnormal Head Position (AHP) - head turn to the opposite side
- Hirschberg (pupil margin=30Δ, limbus=90Δ) - Exotropia
- (Lids normal) - must exclude CNIII palsy
- (Pupils normal) - must exclude CNIII palsy
- ± Conjunctival scarring of prior surgery
4. Cover-Testing
- Exotropia greater on head turn to same side (i.e. incomitant)
5. Ocular Rotations
- Limitation of adduction
- ± X-pattern (SO / IO tightening)
“Paretic”
MR Underaction (Slipped or Over-recessed)
Restrictive
LR Tight / Fibrosed (over-resected)
Ductions
“Paretic”
MR Underaction (Slipped or Over-recessed)
> Versions
Restrictive
LR Tight / Fibrosed (over-resected)
= Versions
Saccades
“Paretic”
MR Underaction (Slipped or Over-recessed)
Slow
Restrictive
LR Tight / Fibrosed (over-resected)
Normal (outside range of restriction)
6. Saccades
“Paretic”
Restrictive
Saccades
“Paretic”
Slow
Restrictive
Normal (outside range of restriction)
7. Dilated Fundus Exam
- Exclude sensory exotropia (macular scar, optic nerve hypoplasia)
8. Measurements
- BI prism on affected side
9. Forced Duction / Generation Testing
“Paretic”
MR Underaction (Slipped or Over-recessed)
Restrictive
LR Tight / Fibrosed (over-resected)
Forced Duction
“Paretic”
MR Underaction (Slipped or Over-recessed)
Normal
Restrictive
LR Tight / Fibrosed (over-resected)
Abnormal
Forced Generation
“Paretic”
MR Underaction (Slipped or Over-recessed)
Abnormal
Restrictive
LR Tight / Fibrosed (over-resected)
Normal
10. Assess the Risk of Post-operative Diplopia
- Prism subjective test (place BI prism over affected side)
- Synoptophore (measure size of suppression scotoma)
- Botox to LR
11. Assess Suitability for Adjustable Sutures
- Can the patient tolerate forced duction testing?
- Does the patient subjectively feel they could cope?
Next
7.0 Introduction
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Vitreoretinal Surgery Online
This open-source textbook provides step-by-step instructions for the full spectrum of vitreoretinal surgical procedures. An international collaboration from over 90 authors worldwide, this text is rich in high quality videos and illustrations.
