Isolated inferior oblique pareses.

Abstract

To describe etiology, clinical characteristics, radiological features and management of isolated inferior oblique pareses. A diagnosis of inferior oblique paresis was made after a thorough strabismus examination and neuroimaging. The patients were managed surgically with adjustable strabismus surgery, or conservatively. Surgical success was defined as average horizontal deviation within ≤ 10 prism diopters [PD] post-operatively and for vertical deviation, it was ≤ 5 PD, at last follow-up. Seven cases were congenital, 6 cases were bilateral, with esotropia in 6 cases; 'A' pattern in 7 cases and hypotropia in 3 cases. The mean preoperative horizontal deviation was 52.5 PD, and the mean postoperative horizontal deviation was 2.37 PD (p = 0.028). The pre-operative vertical deviation was 18 PD and post-operative vertical deviation was 5 PD. MRI showed reduced IO muscle size; average area being 11.27mm2 in the affected eyes, with normal sized inferior recti (average: 24.63mm2) and medial recti muscles (average: 30.08mm2). Surgical success was seen in all six cases. Average follow-up was 265days. The Parks' three step test was not valid, except for one acquired unilateral case. Isolated pareses of inferior oblique muscle exhibit defective elevation in adduction of the affected eye, 'A' pattern and fundus intorsion, and is confirmed by neuroimaging. These can be successfully managed surgically to correct the deviation.