6.10 Consecutive Exotropia

Definition

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:

  1. Post-operative following exotropia surgery (infantile or accommodative ET)
  2. Spontaneous

Examination Structure

1. Visual Acuity (Best Corrected)

  • Exotropic eye may be amblyopic

2. Spectacles

  • BI prism- apex points towards the deviation

3. Inspection

  1. Abnormal Head Position (AHP) - head turn to the opposite side
  2. Hirschberg (pupil margin=30Δ, limbus=90Δ) - Exotropia
  3. (Lids normal) - must exclude CNIII palsy
  4. (Pupils normal) - must exclude CNIII palsy
  5. ± Conjunctival scarring of prior surgery
Figure 6.10.1 Consecutive Exotropia

Figure 6.10.1
Consecutive Exotropia

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

  1. Prism subjective test (place BI prism over affected side)
  2. Synoptophore (measure size of suppression scotoma)
  3. Botox to LR

11. Assess Suitability for Adjustable Sutures

  • Can the patient tolerate forced duction testing?
  • Does the patient subjectively feel they could cope?

          

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