Preoperative prism adaptation test in normosensoric strabismus.

In 19 patients with normosensoric esotropia, the squint angles measured with the alternate cover test were compared with those after prolonged prismatic correction of the squint angle and with those after prolonged occlusion of one eye. All patients showed an increase of the squint angle after prism adaptation. The angle was generally smaller after diagnostic occlusion of one eye than after prism adaptation. We assume that the increase in the squint angle after prism adaptation is caused by an anomalous sensorial relationship between the two eyes that was not detected with the usual psychophysical tests. Surgery tailored to the squint angle after prism adaptation seems advisable in patients with normosensoric esotropia.