Factors Affecting the Surgical Outcome of Primary Exotropia

Abstract

Aims To identify the predictors for motor outcome and response to surgical treatment of primary exotropia. Setting Taunton and Somerset Hospital, Somerset, United Kingdom. Study type Retrospective analysis of the surgical treatment of primary exotropia performed in our department over a period of 12 years from April 1991 to May 2003. Methods Case-notes of the patients who had surgical treatment for primary exotropia for the specified period were identified by a hospital computer database (MDI coding). All case-notes were reviewed and the following data were recorded and used for statistical analysis: age at the time of surgery, type and severity of exotropia, presence of amblyopia, AV pattern and vertical deviation, the level of stereopsis, type of surgery, and motor and cosmetic results. The surgical outcome was determined as good motor outcome if tropia was within 10 PD of orthotropia. The response to surgery was derived from the difference between the preoperative and postoperative angle of deviation for distance per amount of muscle surgery in millimetres. Results A total of 124 cases were included in the study. Good motor outcome was achieved in 83 (67%) cases. There was a positive correlation between the preoperative angle of deviation at distance and dose response to surgery (r = 0.6 and p < 0.001) and a negative correlation between average corrected visual acuity and response (r = −0.21 and p = 0.025). There was a statistically significant negative relationship between preoperative stereopsis and response to surgery (p = 0.02). Conclusions Surgical treatment for exotropia is effective and the dose response is correlated to the preoperative angle of deviation and average visual acuity. Poor or no preoperative stereopsis was associated with better response to surgery.