Interocular equality of tonic accommodation and consensuality of accommodative hysteresis.

Interocular differences in tonic accommodation were assessed before and after a 10 minute period of sustained monocular fixation. The fixation task was carried out once for each eye using a high-contrast target at near, and once for each eye using an empty illuminated field. Tonic accommodation increased significantly as a result of fixating the high contrast target at near, but remained stable when viewing the empty field. Close correspondence was found between the two eyes with respect to both prefixation tonic level and magnitude of tonic after-effect. Absence of interocular differences clearly demonstrates the consensuality of accommodative hysteresis.