COMPONENTS OF VISUAL-ACUITY LOSS IN STRABISMUS

Strabismus, the misalignment of the visual axis of one eye relative to that of the other eye, reduces visual acuity in the affected eye. Sev eral processes contributing to that loss are: amblyopia, which results in a chronic acuity loss whether or not the fellow eye is viewing; st rabismic deviation, which shifts the image of an acuity target onto mo re peripheral, and therefore less acute, retina when the fellow eye fi xates; interocular suppression and binocular masking, which reduce vis ibility in the strabismic eye due to neural influences from the other eye. We measured the losses due to these processes in nine small-angle strabismic subjects. Amblyopia reduced acuity by a median of 34% rela tive to its value in subjects with normal binocular vision, and strabi smic deviation produced a loss of 44%. Suppression and masking togethe r reduced acuity by 20%, and therefore had substantially less effect t han the other factors.