Binocular inhibition in strabismic patients is associated with diminished quality of life

PURPOSE To characterize the relationship between binocular summation (BiS) and binocular inhibition (BI) on the quality of life of adults and children with strabismus. METHODS Strabismus patients at a single center from 2010 to 2012 were prospectively enrolled. A BiS score was measured using ETDRS and Sloan low-contrast visual acuity (LCA) protocols at 2.5% and 1.25% contrast. Patients were categorized as having BiS (binocular better than better-eye visual acuity by >= 5 letters), BI (binocular worse than better-eye visual acuity by >= 5 letters), or otherwise indeterminate visual acuity (a difference between binocular visual acuity and monocular visual acuity of the better eye of <5 letters). Quality of life was evaluated by the National Eye Institute Visual Functioning Questionnaire 25 (VFQ-25), 20-item Adult Strabismus Questionnaire (AS-20), and the Amblyopia and Strabismus Questionnaire. RESULTS A total of 108 patients were included. There was no significant BiS or BI for high-contrast ETDRS or 2.5% LCA tests; however, a mean BiS score of -2.14 +/- 7.0 letters for 1.25% LCA demonstrated significant binocular inhibition (P = 0.004) for this contrast level. The mean composite VFQ-25 score was significantly lower in subjects with BI on ETDRS (80 +/- 19 vs 57 +/- 7 for subjects with BiS and BI, resp. [P = 0.03]), 2.5% LCA (81 +/- 14 vs 66 +/- 16 for subjects with BiS and BI, resp. [P = 0.01]), and 1.25% LCA tests (91 +/- 9 vs 72 +/- 14 for subjects with BiS and BI, resp. [P = 0.005]). After accounting for potential covariates, significant association persisted for BI, demonstrated by 1.25% LCA (P = 0.01). With BI demonstrable at 2.5%, AS-20 scores were also significantly lower (P = 0.04). CONCLUSIONS Strabismic patients with BI had significantly lower quality-of-life scores than those who did not, even after accounting for potential covariates and the absence of diplopia. (J AAPOS 2014;18:423-426)