To investigate the efficacy and safety of slanted bilateral lateral rectus recession (S-BLRc) for the treatment of convergence insufficiency-type intermittent exotropia (CI-IXT) in children.

This was a retrospective case-control study. Fifty-eight patients with CI-IXT, aged 4 to 10 years old, underwent S-BLRc procedures. All the patients were grouped based on the different slanted amounts between the upper and lower poles of the lateral rectus: Group A (1 mm, n=22), group B (1.5 mm, n=18), and group C (2 mm, n=18). The preoperative and postoperative data included deviations both at near and at distance, the near-distance difference (NDD), objective torsion, horizontal deviation at up and down gaze, binocular vision, surgical success rate and refractive errors among the three groups and were analyzed and compared. The successful surgical outcome was defined as deviation ranging from exotropia <-8 ^△ to esotropia <5 ^△ both at near and distance as well as the NDD<5^△. The preoperative and postoperative data were compared using a paired t-test. The data among the three groups were compared using one-way ANOVA. The improvement in stereopsis and surgical success rates among the three groups were analyzed using a Fisher's exact test.

The average deviations significantly decreased from -37.1^△±4.2^△ (exotropia) to -1.4^△±4.6^△ at near and from -25.8^△±3.7^△ to -0.1^△±4.1^△ at distance (t=45.72, P<0.001;t=32.54, P<0.001). The NDD was significantly reduced from 10.0^△±0^△ to 1.8^△±1.9^△ in Group A, from 11.2^△±1.5^△ to 0.8^△±2.1^△ in Group B and from 13.3^△±2.2^△ to 0.9^△±2.5^△ in Group C (t=20.30, P<0.001;t=17.24, P<0.001;t=13.64, P<0.001). There were significant differences in the mean corrections of NDD among the three groups (8.2^△±1.9^△, 10.3^△±2.5^△, 12.4^△±3.9^△, respectively) (F=10.80, P<0.001). There was no significant difference in the AC/A ratios before and after the operation. All patients obtained various improvements in stereopsis after surgery. There was no significant difference in the spherical refractive error and the axis of astigmatism between the groups before and after the operation. At 6 months after surgery, the differences in astigmatism between before and after operation were still remarkable (t=5.06 in the right eye, 5.32 in the left eye; both P<0.001). None had torsional diplopia or A-V pattern. The surgical success rate was 89.7% in our study and there was no significant difference in success rates among the three groups.

S-BLRc is an effective and safe procedure for the treatment of CI-IXT in children. S-BLRc can successfully collapse exotropia at distance and at near and NDD and the benefit is a gain in binocular vision. The correction of NDD is associated with the degree of the slant.

inermittent exotropia; convergence insufficiency; slanted bilateral rectus recession; near distance difference