Distance stereopsis in orthophores, heterophores, and intermittent strabismics.

The purpose of this study was to investigate the value of clinical testing of distance stereopsis. Distance stereopsis was assessed with the Mentor Binocular Vision Testing System (B-VAT) system for 45 patients with ocular deviations of 6 delta or more at distance (heterophoria and intermittent strabismus) and for 36 patients with orthophoria. On the average, distance stereopsis was better for patients with the smaller ocular deviations than for those with the larger ocular deviations. The mean distance stereoacuities, both contour and global, for the orthophores were 53 and 81 sec arc, for the heterophores 93 and 100 sec arc, and for the intermittent strabismics 95 and 169 sec arc. Although the average size of the deviation at distance and near for the heterophoric and strabismic patients was nearly the same, distance stereopsis tended to be poorer than near stereopsis. There was a significant difference between the proportion of orthophores and the proportion of intermittent strabismics exhibiting distance stereopsis with both contour and global stereo targets (p < 0.05).