Operant measurement of subjective visual acuity in non-verbal children.

The present experiment sought to develop a reliable procedure for measuring visual acuity in non-verbal retarded children. Five non-verbal retarded children and two literate adults were examined. The two adults were included in the experiment so that verbal communication with them could validate certain assumptions regarding the experimental procedures. By utilizing a lever press as the criterion response signifying a visual discrimination and employing the Snellen "E" discriminanda, a reliable subjective measure was obtained, not unlike those measures taken from verbal adults. Contrary to several antecedent procedures, a relatively precise measurement of subjective acuity was shown to be obtainable from non-verbal retarded children. Additionally, the procedure was successful in evaluating the effectiveness of prosthetic lenses previously prescribed for two of the children.