Clinical observation of the graduated "hang-back" recession of superior oblique in a-pattern strabismus with superior oblique overaction

Abstract

To investigate the effect and safety of the graduated "hang-back" recession of superior oblique (SO) in treatment of A-pattern strabismus with superior oblique overaction (SOOA). Retrospective study. The clinical data of 15 cases (28 eyes), who underwent graduated "hang-back" recession of SO depending on the scales of SOOA, were collected and analyzed. The principle we carried on was hang-back recession 8-10mm for SOOA+4, 6 to 8 mm for SOOA+3, 5 to 6 mm for SOOA+2 and 4 mm for SOOA+1. The pre-operative and post-operative outcomes, including the ocular alignment, ocular motility, A-pattern and objective torsion demonstrated by fundus photographs were evaluated and compared. In 15 cases (28 eyes), 2 cases had unilateral hang-back recession of SO for unilateral SOOA. Thirteen cases had bilaterally symmetric or asymmetric hang-back procedure. All the patients had no A pattern after surgery. The average difference of pre- and post-operative A-patterns were (24.5±11.9) PD and (3.2±4.2) PD in 13 cases with bilateral SOOA (t=8.01, P=0.00). The bilateral SO hang-back procedure could correct A-pattern in an amount of 21.3±10.3 PD in average. The average amount of pre- and post-operative SOOA were +3.0±2.0 and +0.5±1.0 in 28 eyes (Z=-4.70, P=0.00). Only 1 case remained residual SOOA+2.0. Fundus photos were measured by SigmascanPro5.0 program and the average pre- and post-operative torsion were +5.4°±3.9°and +0.3°±5.6° (The baseline was the line across the center of optic disc. The torsional angle was measured between the line across the fovea and and the line across the center of optic.) in 28 eyes (t=5.76, P=0.00). The average corrected torsion was 5.2°±4.8°. The pre-operative SOOA was related with the pre-operative torsion (Spearman correlation coefficient=0.47, P=0.01). The surgical amounts in 28 eyes were various from 4 to 10 mm (8±12 mm in average), which were not related with the corrected torsion (Spearman correlation coefficient=0.17, P=0.39), but related with pre-operative torsion (Spearman correlation coefficient=0.44, P=0.02). The total amounts on both eyes in patients operated by bilateral SO hang-back procedure were also not related with the corrected A-pattern (Spearman correlation coefficient=0.55, P=0.05). No case had secondary SO palsy and V-pattern after surgery. The graduated "hang-back" recession of SO is optional for treatment of mild to moderate SOOA and A-pattern. It corrected objectively in-torsion without risks of secondary SO palsy and V-pattern. It is a safe and effective SO weakening procedure. (Chin J Ophthalmol, 2016, 52: 579-583).