Aims To compare the postoperative surgical outcomes and the changes in deviation achieved per millimetre of recession in patients treated by graded unilateral medial rectus (UMR) or bilateral medial rectus (BMR) recession for small to large angle esotropia with a minimum follow-up of 6 months.

Methods In a retrospective, consecutive and interventional case series, 102 patients underwent UMR recession and BMR recession for constant esotropia measuring 15–35 prism diopters (PD) and 30–70 PD, respectively, from 1 January 2007 to 30 September 2010. Successful alignment was defined as ±8 PD of orthophoria in primary and lateral gaze.

Results No significant difference was observed between: (1) the success rates of the BMR and UMR recession groups at postoperative days 1∼3 (p=1.00) or at final follow-up (p=0.421); (2) the variation in the mean change in deviation from postoperative days 1∼3 to the final follow-up of the UMR (p=0.58) and BMR (p=0.56) recession groups; and (3) the mean correction in PD per millimetre of muscle recession in the UMR and BMR (p=0.63) recession groups.

Conclusion Graded UMR recession for 15–35 PD of esodeviation was as effective as graded BMR recession for 30–70 PD of esodeviation. There was no statistical difference in changes in deviation per millimetre of recession between equivalent amounts of unilateral and bilateral recession.