Effect of Modified Vertical Rectus Belly Transposition vs Augmented Superior Rectus Transposition Plus Medial Rectus Recession for Chronic Sixth Nerve Palsy A Randomized Clinical Trial

IMPORTANCE Both vertical rectus belly transposition (VRBT) and superior rectus transposition (SRT) can be performed simultaneously with ipsilateral medial rectus recession (MRc) and have been shown to be effective for chronic sixth nerve palsy. However, it is unclear whether VRBT is superior to SRT in correcting esotropia. OBJECTIVE To compare the effectiveness of modified VRBT plus MRc (mVRBT-MRc) vs augmented SRT plus MRc (aSRT-MRc) in Chinese patients with chronic sixth nerve palsy. DESIGN, SETTING, AND PARTICIPANTS This parallel-design, double-masked, single-center, randomized dinical trial was conducted from January 15, 2018, to May 24, 2021. The follow-up visits were scheduled at 1 month and 6 months. Eligible Chinese participants with unilateral chronic sixth nerve palsy were randomly assigned to receive either mVRBT-MRc (VRBT group) or aSRT-MRc (SRT group). INTERVENTIONS mVRBT-MRc or aSRT-MRc. MAIN OUTCOMES AND MEASURES Change of horizontal deviation in primary position from baseline to 6 months. RESULTS Of the total 25 eligible participants, the mean (SD) age was 45.4 (12.6) years, with 10 male participants (40%) and 15 female participants (60%). Thirteen participants (52%) were randomly assigned to the VRBT group, and 12 (48%) were randomly assigned to the SRT group. At baseline, the mean (SD) horizontal deviation was 65.7 (10.8) prism diopters (Delta) in the VRBT group and 60.5 Delta (14.1 Delta) in the SRT group. Similar amounts of MRc were performed in both groups. At 6 months, the horizontal deviation changed from baseline by 66.3 Delta in the VRBT group and by 51.5 Delta in the SRT group. The adjusted group difference was 10.9 Delta (95% CI, 5.3 Delta-16.6 Delta), favoring the VRBT group (P = .001). Four times as many participants corrected more than 60A with mVRBT-MRc compared with aSRT-MRc. The group difference of the improvement of abduction limitation was -0.2 (95% CI, -0.8 to 0.5; P = .64). Although there was a higher proportion of undercorrection in the SRT group (difference, 45%; 95% CI, 16%-75%; P = .01), no differences were identified for other suboptimal outcomes between groups. CONCLUSIONS AND RELEVANCE Compared with aSRT-MRc, mVRBT-MRc showed better effect in correcting esotropia with no differences detected for other suboptimal outcomes. mVRBT-MRc may be a promising alternative surgical procedure for chronic sixth nerve palsy, particularly for large esotropia of more than 60 Delta, if these results are confirmed in larger, diverse cohorts with longer follow-up.