Refractive and Corneal Topographic Changes after Hangback Strabismus Surgery

Refractive change after strabismus surgery is a known phenomenon which may be attributed to the extraocular muscle traction.Since previous studies were often done by conventional methods,accompanied by a short follow-up, and without considering simultaneous evaluation of both refractive and topographic changes, this study was organized to evaluate refractive and topographic changes after strabismus surgery by hangback method. Patients and In this prospective, interventional,and case series study, 53 eyes of 33 patients undergoing hangback strabismus surgery were studied. Cyclorefraction with autorefractometer and topographic evaluation were done before and 2 weeks, 2 months, and 6 months after the operation. Data were analyzed by SPSS software version 15 using t- test and Chi-square test. The mean age of the subjects was 17.7 ± 10.2 years. We performed medial rectus recession on 18 eyes, lateral rectus recession on other 18 eyes, and simultaneous recession-resection on the remaining cases. In comparison to preoperative astigmatism, mean surgically induced astigmatism evaluated by cyclorefraction 2 weeks, 2 months, and 6 months postoperatively was 0.17± 0.52, 0.35±0.62 and 0.11±0.27 diopters, respectively. The overall axis shift was toward 180 (2, 24, and 15 degrees respectively)(in all cases p<0.05). Mean surgically induced astigmatism evaluated by topographic data was 16±0.97, 0.53±1.2, and 0.29±0.63 diopters (in all cases p<0.05). The overall flat meridional shift was toward 180 (30, 25, and 7 degrees respectively). Comparing astigmatic changes in topography with those in cyclorefraction revealed a statistically significant difference in the second week measurements and not in other measurement times. Hangback surgery can induce refractive changes and astigmatism, which may be due to corneal changes. Surgically induced changes reach a maximum amount in 2 months, and despite shifting toward baseline, will persist for 6 months.