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Corneal astigmatic effects of conventional recession vs suspension recession ("hang-back") strabismus surgery: a pilot study.

INTRODUCTION
Changes in refractive error after strabismus surgery occur secondary to changes in corneal curvature. The change in refractive error is usually transient but may lead to a temporary decrease in vision. We compared the change in corneal curvature following strabismus surgery in eyes utilizing a suspension (so-called "hang-back") recession technique to eyes undergoing conventional recession surgery.


METHODS
Sixteen patients undergoing bilateral medial or lateral rectus recessions were prospectively entered into the study. One eye was randomly selected to undergo conventional strabismus surgery and the other eye underwent strabismus surgery using the suspension technique. Keratometry measurements were taken in the operating room immediately prior to and immediately after surgery. The change in corneal curvature was calculated and analyzed for each technique.


RESULTS
The mean change in corneal curvature was -0.06 diopters (D) for the suspension group and +0.18 D for the conventional group, confirming prior reports. However, all eyes undergoing suspension surgery had a change within 1 D whereas only 75% of those eyes undergoing conventional surgery fell within the same range. Overall there was twice the variation in the degree of astigmatism in the conventional group when compared with the suspension group.


CONCLUSIONS
No eye undergoing suspension surgery experienced a change in corneal curvature greater than 1 D while 25% of those undergoing conventional surgery did. Therefore, possible benefits to the suspension recession technique might include less overall variability of astigmatism change and decreased amounts of induced astigmatism. Patients undergoing strabismus surgery using a suspension technique may be less likely to notice a change in their vision in the immediate postoperative period.