Increasing the proportion of binocular vision makes horizontal prism adaptation complete.

In previous phoria adaptation experiments on normal subjects adaptation tends to reach only approximately 2/3 of the prism-induced phoria while clinical experience indicates that prism adaptation is usually complete. The present data show that increasing the proportion of binocular experience through the phoria-inducing prism allows adaptation to become complete. Longer periods of binocular vision give a better indication of vergence adaptation function. This is particularly important in experiments where normal and abnormal adaptive abilities are being compared.