To compare the changes in strabismus angle and deviation between two groups: a bilateral lateral rectus recession (Group 1) and a unilateral lateral rectus recession in exotropia (Group 2).

A retrospective survey was conducted on 198 patients who had received exotropia surgery in our ophthalmology clinic from September 2003 to April 2007. A total of 116 patients were in Group 1, and 82 patients were in Group 2.

Unilateral lateral rectus recession was performed on patients under 25 PD, and bilateral lateral rectus recession was performed on patients above 25 PD. A case of less than 4 PD esodeviation and less than 10 PD exodeviaton was defined as a success and any other case as a failure at the 1-year follow-up visit.

The average deviations of the first postoperative month and the first postoperative year were -1.96 D ± 4.75, 2.5 D ± 7.82 for Group 1 and 0.77 D ± 2.87, 5.94 D ± 3.38 for Group 2. Revealing statistical significance between the 2 Groups: Group 1 had 30 failure cases (25.9%) and their 1 postoperative year average deviation was 5.42 D ± 13.97, while Group 2 showed 24 failure cases (29.3%) and their 1-postoperative-year average deviation was 13.0-79 ± 3.04. Group 1 had less strabismus angle and a greater standard deviation than Group 2, as Group 1 had more overcorrection. Among the 30 failure cases of Group 1, 9 were overcorrected and 21 were undercorrected, but all 24 failure cases in Group 2 were undercorrected.

The strabismus angle after lateral rectus recession showed a wider variation and a larger difference in bilateral lateral rectus recession than in the unilateral lateral rectus recession.