PURPOSE: Using corneal reflex, we performed intraoperative adjustments in horizontal strabismus patients who had very poor visual acuities with good compliance and analyzed various aspects of intraoperative adjustment. METHODS: We retrospectively reviewed the records of patients with horizontal strabismus who underwent intraoperative adjustment using corneal reflex from May 1997 to April 2005. We evaluated various aspects of intraoperative adjustment. RESULTS: Fifty-five patients (40 exotropes, 15 esotropes) were included in our study. 11 of 40 extropes (27.5%) and 4 of 15 esotropes (26.7%) eventually underwent operations that were adjusted intraoperatively. Successful results were seen in 35 of 40 exotropes (87.5%) and 8 of 15 esotropes (53.3%). Fifteen patients (27.3%) received intraoperative adjustments, and of these patients 11 (20.0%) who had successful results would have experienced either undercorrection or overcorrection if their operation were performed as scheduled. Four patients underwent operation on one muscle rather than on the scheduled two muscles. All 4 of these patients (100%) would have experienced significantly large overcorrection had they not received intraoperative adjustment. CONCLUSIONS: Patients who would have had difficulty with fixation due to low visual acuity could avoid under- or overcorrection and are expected to have higher success rates because of intraoperative adjustment using corneal reflex.