To determine the role of lateral rectus hypofunction (LRHOF) as a possible risk factor of reoperation in infantile esotropia (IET) patients.

This case-control study was performed on 215 (430 eyes) IET patients from 2010-2015 at Imam Hossein and Torfeh Eye Medical Centers, Tehran, Iran. Patients with a history of IET up to age of 6 months, stable preoperative deviation≥30pd and at least 3 months follow-ups were included. Cases with early onset accommodative esotropia, congenital cataract, retinopathy of prematurity, manifest nystagmus, fundus lesions, neurological and ophthalmic anomalies, 6th nerve palsy, Duane’s syndrome were excluded. After three months post-surgery, children were classified into two the success (deviation≤10pd) and the failure (deviation>15pd) groups. Preoperative function of Lateral rectus (LR) was denoted based on 0 to -3 grading scale.

In this study, 116 females and 99 males with administration age of 4.70±6.30 years were included. The surgical age was significantly higher in the failure group (P<0.044). The first surgical age up to 5 years had no effect on the surgical outcome, but after that the results were different (p=0.016). Grades -0.50 and -1 of LRHOF did not show any differences regarding the success or reoperation rates, while grades -2 (p<0.025) and -3 (p<0.028) of LRHOF caused less success and more reoperative rates (p<0.003). The age at the first operation was not a reoperation risk factor in different grades of LRHOF.

Based on results, the obvious clinical LRHOF in IET cases would increase the reoperation rate; therefore it is recommended to inform their parents, preoperatively.