Factors Predisposing to Amblyopia After Exotropia Surgery

Amblyopia (lazy eye) is one of the significant complications of strabismus surgery. It is the most important cause of unilateral visual impairment in both children and adults. The current investigation was achieved to determine the postoperative amblyopia rate and to identify factors predisposing to amblyopia following exotropia surgery among patients who had been referred to Imam Khomeini Hospital in Urmia, Iran. The present investigation is a retrospective study that was conducted over three years (2008-2010). The study consisted of sixty patients who underwent their first strabismus surgery for treatment of horizontal deviation. Patients were followed up for at least 24 months, and the rate of postoperative amblyopia was measured. The preoperative deviation, strabismus type (exotropia vs. esotropia), visual acuity, age at surgery, and the number of operated muscles were analyzed as determining factors of postoperative development of amblyopia. Amblyopia was observed in 50% of cases during the follow-up period. No statistically significant differences were observed between amblyopic and non-amblyopic eyes in terms of sex, age at surgery, strabismus type, and visual acuity. But amblyopic eyes showed higher deviation angles compared to non-amblyopic eyes (<0.001). The Cox hazard model analysis revealed a significant contribution of deviation angle to postoperative development of amblyopia. A larger deviation angle has been identified as a positive predictor of postoperative development of amblyopia in our investigated population. Due to such a high rate of postoperative amblyopia, it seems better to initiate and complete amblyopia therapy before strabismus surgery.