Deficiency of depression in adduction: Clinical characteristics and surgical management of the "inverted Brown pattern"

Purpose To evaluate the clinical characteristics and surgical management of patients with an "inverted Brown pattern," which is defined clinically as a hypertropia with greatest deviation in down-and-in gaze of the higher eye, having the appearance of superior oblique muscle underaction but without significant inferior oblique muscle overaction. Methods The medical records of patients with this misalignment pattern who had cyclovertical muscle surgery at our institution from 2003 through 2015 were retrospectively reviewed; medical records were analyzed for pre- and postoperative motility patterns, fundus torsion, intraoperative findings, and type of strabismus surgery. Results A total of 45 patients presenting with a hyperdeviation worse in down-and-in gaze of the higher eye were included in the study. Of these, 25 (56%) had previously had inferior oblique-weakening procedures. The remainder included those with untreated superior oblique paresis (22%), previous orbital trauma (18%), or other ocular surgery (4%). The mean preoperative hyperdeviation in straight-ahead gaze was 8.7^Δ, compared with 0.9^Δ postoperatively. Surgical success, defined as the absence of diplopia in straight-ahead gaze and not requiring further cyclovertical surgery, was achieved in 78% of patients. Conclusions The motility pattern referred to as the "inverted Brown pattern" can develop in patients with orbital trauma, as previously described, or in association with superior oblique muscle paresis, most commonly after prior surgery to weaken the inferior oblique muscle. Weakening or reweakening of the inferior oblique muscle appears to correct this misalignment pattern, despite the absence of significant inferior oblique overaction preoperatively.