تغییرات رفراکتیو و توپوگرافیک قرنیه پس از عمل جراحی

  Background & Aim: 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 Method : 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.   Results :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.   Conclusion: 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.