Surgical outcomes for unilateral superior oblique palsy in Chinese population: a retrospective study.

AIM To evaluate the outcome after surgery for unilateral superior oblique (SO) palsy in Chinese. METHODS The medical records of 39 patients that underwent surgery for unilateral SO palsy between January 2003 and December 2012 at Caritas Medical Centre, Hong Kong, were retrospectively reviewed. All surgeries were performed by a single surgeon. Pre-operative assessments for vertical deviation, cyclo-deviation, and Knapp's classification were obtained to determine the nature and degree of surgical correction. Vertical deviation was measured at 1wk; 1, 6mo and on last follow-up day post-operatively. Cyclo-deviation was measured on last follow-up day post-operatively. RESULTS During the 10y period, 39 subjects were recruited. The most common etiology was congenital (94.9%). Knapp's Type III (66.7%) and Type I (12.8%) classifications were the most common subtypes. To treat SO palsy, the most common surgical procedures were: isolated inferior oblique (IO) anteriorization (41.0%), isolated IO myectomy (10.3%), and isolated IO recession (10.3%). At 3.5±2.1y post-operatively, the vertical deviation was significantly reduced (15.1±6.2 PD versus 0.5±1.4 PD, P<0.0001) without significant improvement in cyclo-deviation (P=0.5). Initial vertical deviation was correlated with cyclo-torsion (r=0.4, P=0.007). Those with over-correction had greater initial vertical deviation (19.4±7.2 PD versus 13.2±4.3 PD, P=0.003). After a single operation, 84.6% of subjects achieved a vertical deviation within ±3 PD. CONCLUSION The majority of subjects achieved corrected vertical deviation after a single surgery although there was no improvement in cyclo-deviation. Those with over-correction of primary position deviation had greater preoperative vertical deviation and it may be related to simultaneous multiple muscle surgery.