Relationship of heterophoria to stereopsis.

Eighty patients with 6/7.5 (20/25) or better visual acuity in each eye noted differences in stereoacuity with crossed and uncrossed disparity. Esophoric patients who perceived a difference were more likely to have greater stereoacuity with uncrossed disparity, and exophoric patients who perceived a difference were more likely to have greater stereoacuity with crossed disparity. Asymmetry of Panum's area may be a factor in this phenomenon.