Title:
Inferior rectus muscle recession as a treatment for vertical diplopia following cataract extraction.

Abstract:
Persistent vertical diplopia may occur after cataract surgery as a rare complication of retro- or parabulbar anesthesia. This is probably caused by structural changes in the muscles, altering muscular elasticity and function and thus complicating setting of the dosage for corrective strabismus surgery. The aim of our study was to investigate the effect of strabismus surgery in this specific motility disorder.
The findings from 15 consecutive patients (six women, nine men, median age 76 years), who had undergone initial strabismus surgery in our eye clinic between 2007 and 2010 due to vertical diplopia following cataract surgery, were investigated retrospectively. In all cases, cataract surgery had been performed under retro- or parabulbar anesthesia.
Preoperatively, all affected eyes (five right eyes, ten left eyes) showed hypotropia with elevation deficiency and overaction of the inferior rectus muscle and/or superior oblique muscle on down-gaze. The median vertical deviation in primary position was 9.1 deg (min. 4.6, max. 24.7), measured with the alternate prism cover test, and 8 deg (min. 3.5, max.18) at the tangent screen of Harms. In all cases, the inferior rectus muscle was recessed 3 to 6 mm (median 3.5 mm). On the first day after surgery, the median angle of squint in primary position was 2.3 deg (min. 0, max. 10.2), when measured with the alternate prism cover test, with a mean dose-effect relationship of 1.8 ± 0.7 deg angle reduction per millimetre recession (median 1.9 deg/mm). In the postoperative period, eight patients examined after 2 to 20 months (median 3.5 months) showed a median vertical deviation of 5.7 deg (min. 1.7, max. 11.3), with a mean dose-effect relationship of 1.7 ± 1.3 deg/mm (median 1.8 deg/mm), but the values ranged widely. Four patients were not examined but interviewed by telephone. There was no feed-back from three patients. Six of 12 follow-up patients had no complaints, three had prisms to correct a persisting angle, and three patients needed further squint surgery.
The efficacy of inferior rectus muscle recession for correction of hypotropia following cataract surgery with local anesthesia ranged widely. In this condition, operating on one muscle is a good option for correction of squint angles of less than 12 deg. Squint angle enlargement can occur in the postoperative course, and may necessitate further surgery.