['To characterize the relationship between binocular summation (BiS) and binocular inhibition (BI) on the quality of life of adults and children with strabismus.', '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\xa0(VFQ-25), 20-item Adult Strabismus Questionnaire (AS-20), and the Amblyopia and Strabismus Questionnaire.', '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).'] Is binocular inhibition in strabismic patients associated with diminished quality of life?