Vertical Tropia Following Horizontal Transposition Surgery.

Aim: The aim of this study was to determine the prevalence of vertical tropia following horizontal transposition of both vertical rectus muscles (HToVR) in patients with Duane syndrome or sixth nerve palsy.

Methods: This retrospective study included patients with Duane syndrome or sixth nerve palsy who had undergone HToVR muscles. Data collected included: age, gender, diagnosis, laterality, pre-operative angle of deviation, type of surgery and post-operative angle of deviation at one week, three months and six months. Information on the use of botulinum toxin (BT) ipsilateral medial rectus (MR), additional surgery was performed, and the presence of preoperative and postoperative binocular function and any vertical deviation was collected.

Results: There were 11 patients, eight patients with a diagnosis of Duane syndrome and three patients with a diagnosis of sixth nerve palsy. The mean age of the patients was 13 ± 14.79 years (range 5-55 years), four were female. The prevalence of post-operative vertical tropia was 54%. The mean vertical deviation for distance, was 7.6^ ± 2.94 (SD) (range 3^-9^). Stereoacuity was present preoperatively in 5 patients and 8 postoperatively. No patient developed diplopia or received further surgery for the vertical tropia. Of the six patients who had intraoperative BT at the time of the HToVR, four developed a vertical deviation.

Conclusion: The prevalence of vertical deviation following HToVR muscles was 54% in our series. None of the patients with an induced postoperative vertical deviation reported diplopia or required further surgery for it.