Abstract: We found four RCTs eligible for inclusion in this review (248 eyes of 151 participants between the ages of 6 months to 22 years). All trials were assessed as having unclear risk of bias overall due to insufficient reporting of study methods. One trial was conducted in Canada and compared anteriorization of the inferior oblique muscle with resection versus anteriorization of the inferior oblique muscle alone; one in the USA compared superior rectus recession with posterior fixation suture versus superior rectus recession alone; and two in the Czech Republic compared anteriorization of the inferior oblique muscle versus myectomy of the inferior oblique muscle. Only one trial reported data that allowed analysis of the primary outcome for this review, the proportion of participants with treatment success. The difference between inferior oblique anteriorization plus resection versus inferior oblique anteriorization alone was uncertain when measured at least four months postoperatively (risk ratio 1.13, 95% confidence interval 0.60 to 2.11, 30 participants, very low-quality evidence). Three trials measured the magnitude of hyperdeviation, but did not provide sufficient data for analysis. All four trials reported a relatively low rate of adverse events; hypotropia, limited elevation, and need for repeat surgery were reported as adverse events associated with some of the surgical interventions. No trials reported any other secondary outcome specified for our review. The four trials included in this review assessed the effectiveness of five different surgical procedures for the treatment of DVD. Nevertheless, insufficient reporting of study methods and data led to methodological concerns that undermine the conclusions of all studies. There is a pressing need for carefully executed RCTs of treatment for DVD in order to improve the evidence for the optimal management of this condition.

Plain-language summary: We conducted the search for studies on 3 August 2015. We found four randomized controlled trials (RCTs) of surgical treatment for DVD. We found no studies evaluating non-surgical treatments. One trial was conducted in Canada and compared a surgical repositioning procedure (anteriorization of the inferior oblique muscle) with or without resection; one in the USA compared surgical weakening of an eye muscle (superior rectus recession) with or without augmentation with a fixation suture; and two in the Czech Republic compared anteriorization of the inferior oblique muscle versus removal of a piece of the inferior oblique muscle (myectomy). Only one of the RCTs examined what we wanted to know: the proportion of participants who had surgical success. There was insufficient information available to determine the differences between any of the surgical procedures with respect to surgical success or any other outcome relevant to our review. The most common adverse events from the surgical procedures were downward drifting of the eye after surgery (hypotropia), limited upward movement of the eye, and need for repeat surgery. All four of the included studies had flaws in design, execution, or both that weaken their conclusions. There is a need for well-designed, rigorously conducted RCTs of treatments for DVD to provide more reliable evidence for the management of this condition.