The effects of strabismus surgery on globe position in the setting thyroid eye disease

Abstract

Surgical management of the strabismus in the setting of thyroid eye disease (TED) may worsen proptosis by releasing restricted muscles from the globe. Previous studies have evaluated the change in proptosis following strabismus surgery, but not the factors that may predict the change in globe position. This study evaluates the effect of strabismus surgery on proptosis in TED and clinical factors that may predict the change in globe position following this surgery. The medical records of all patients undergoing strabismus surgery for TED between September 2011 and May 2012 were retrospectively examined. Data collection included sex; dates of birth, decompression surgery, and strabismus surgery; predecompression, post-decompression, and post-strabismus exophthalmometry measurements and alignment in primary and down gaze; types of decompression and laterality performed; intraoperative forced duction findings at time of strabismus surgery; and type and amount of strabismus surgery performed on each eye. Statistical analysis consisted of paired t tests regarding change in exophthalmometry before and after decompression and strabismus surgery. Multiple regression analysis was used to evaluate the predictive value of several preoperative variables. Twenty-one patients were identified, 16 of whom underwent unilateral strabismus surgery and 5 of whom underwent bilateral strabismus surgery. 15 patients (71.53%) were female. Mean intraoperative forced ductions (maximal restriction identified, on a scale from 0 to 4) were 2.45 (SD 0.65), and mean amount of strabismus surgery performed (cumulative recession) was 8.05 mm (SD 3.63 mm). Mean predecompression, post-decompression, and post-strabismus surgery exophthalmometry measurements were 24.78 (SD 3.95), 19.55 (SD 4.88), and 20.95 mm (SD 5.59), respectively. Decompression reduced exophthalmometry measurements by a mean of 5.0 mm (SD 3.62 mm; paired t test; P < 0.0001). Strabismus surgery increased exophthalmometry measurements by a mean of 1.4mm (SD 1.73 mm; P = 0.0013). Multiple regression analysis of possible predictive variables showed that predecompression exophthalmometry is the only independent predictor of exophthalmos after strabismus surgery (P = 0.03). Strabismus surgery on patients with TED significantly increases proptosis. This study suggests a relationship between predecompression exophthalmometry and the change in exophthalmos following strabismus surgery: the more proptotic the patient is prior to decompression, the greater the increase in proptosis after strabismus surgery. Exophthalmometry prior to decompression may indicate the degree of orbital congestion and account for its predictive value for proptosis following strabismus surgery. More aggressive decompression may be warrated in TED patients with greater exophthalmometry to anticipate the increased proptosis from subsequent strabismus surgery.