Magnetic Resonance Imaging of Globe Translation in Abducens Palsy.

PURPOSE:It has been supposed that rectus muscle paralysis would cause proptosis due to the reduction in active posterior tension. This study aimed to test this proposition by evaluating globe translation during horizontal duction in patients with abducens palsy. DESIGN:Prospective, single-center, fellow-eye controlled, case series. METHODS:Horizontal globe rotation and translation were quantified using orbital magnetic resonance imaging of patients with isolated unilateral abducens nerve palsy without other ocular motility disorders. Unaffected fellow eyes served as the control group. Digital image analysis was performed. RESULTS:The study included 5 female and 2 male patients with a mean ± standard deviation age of 52 ± 15 years. The average esotropia was 39.0 ± 9.6 diopters. Mean adduction was similar at 54.9 ± 10.4° in palsied eyes and 52.0 ± 7.1° in fellow eyes. However, abduction in palsied eyes was significantly less at 11.4 ± 7.1° than 37.1 ± 11.4° in fellow eyes (P = .0023). Average anterior translation in adduction was 0.46 ± 0.42 mm in palsied orbits, similar to 0.35 ± 0.47 mm in fellow orbits (P = .90). Anterior translation in abduction averaged 0.17 ± 0.53 mm in palsied orbits, similar to 0.27 ± 0.73 mm in fellow orbits (P = .80). Average medial translation in adduction at 0.32 ± 0.23 mm in palsied orbits was statistically similar to 0.12 ± 0.44 mm in fellow orbits (P = .54). Average lateral translation in abduction at 0.19 ± 0.18 mm in palsied orbits was similar to 0.33 ± 0.15 mm in control orbits (P = .38). CONCLUSION:Abducens palsy does not alter normal eye translation during horizontal duction.