Surgical Outcomes in Intermittent Exotropia

Surgical Outcomes in Intermittent Exotropia
Presentation lecture by:
Jeffrey D. Colburn, M.D., PGY-3
Preceptor: David Morrison, M.D.
Vanderbilt Eye Institute

Intermittent Exotropia

* Intermittent exotropia x(t) is a latent tendency (phoria) for the eyes to turn out, which is intermittently controlled by fusional convergence.
* Characteristics
o Typically good bifoveal fusion and stereoacuity when aligned.
o Amblyopia is rare in x(t).
o X(t) Tends to remain stable or progress.
o Progression might result in dense suppression.

Intermittent Exotropia

* X(t) Sub-types
1. Basic
+ Angle is equal at near & distance

2. Pseudo-divergence excess (PDE)
+ Angle is equal at near & distance but appears larger in distance because of masking

3. True divergence excess (TDE)
+ Angle is larger in distance

4. Convergence insufficiency (CI)
+ Angle is larger at near

Surgical Treatment

* Goals
o Improve alignment & control
o Improve binocular vision
* Basic concepts
o Recession (weakening procedure)
o Resection (strengthening procedure)
* Two primary approaches
o Bilateral lateral rectus recession (BLRc)
o Unilateral recess & resect (R&R)

Predictors of Outcomes

age
pre-op deviation
pre-op control
sub-type
procedure type
asymmetric accommodation
pre-op deviation
central fusion or stereopsis
Observations

* Effect of pre-operative angle size on surgical outcomes in x(t) patients.
* Disparate opinions on the more successful procedure for x(t).
Hypotheses
* Larger angle x(t) patients have more successful surgical outcomes than smaller angle x(t) patients.
* R&R procedures have more successful surgical outcomes than BLRc in the management of x(t).
Methods

* Retrospective chart review
o Inclusion criteria
+ X(t) surgical cases
+ January, 2003 through January, 2008
+ Age ≤ 18 years
Methods

* Exclusion criteria
o Developmental delay
o Vertical deviation
o Pattern deviation
o Prior surgery
o Partially or untreated amblyopia
o Monocular exotropia
o Constant exotropia
o Secondary exotropia
o Nystagmus

Data collection

* Variables considered
o Gender
o Age at time of surgery
o X(t) sub-type
o Pre-op deviation
o Stereo-acuity
o Presence of fusion
o Presence of suppression
o Procedure type
o Deviation post-op visit #1
o Deviation post-op visit #2

Outcome Measures

* Surgical success:
o Intermittent exotropia ≤ 8 PD
o No esotropia
* Surgical failure:
o Not meeting above success criteria
o Repeat surgery for poor control
* Time to surgical failure
* Over-correction or under-correction

Demographics
History of amblyopia
Average pre-op deviation (PD)
Mean age at surgery (mos)
Characteristic Results

* Overall outcomes
o 61 BLRc, 19 R&R, 2 unilateral LRc
o 42 (51.2%) patients failed
o Mean time to failure was 6.9 months (1-34)
o 35 patients (43%) were under corrected
o 6 patients (7.3%) were over corrected

Other variables
Multivariate logistic regression
Surgical procedure (blrc vs. r&r)
Presence of suppression
Presence of fusion
Stereo acuity
Pre-operative deviation
Chi-square
Multivariate survival analysis
Cox proportional hazards model
Surgical procedure
Stereo Acuity
Presence of Suppression
Comment
Summary

Surgical Outcomes in Intermittent Exotropia.ppt