Studies in industrial vision. I. The validity of lateral phoria measurements in the Ortho-Rater

Abstract

Measurements of large numbers of subjects with various techniques lead to the following conclusions: "It would seem that phoria measures in a stereoscope have more or less in common with measures at a true distance according to certain characteristics of the instruments. In the Bausch and Lomb Ortho-Rater, a 13-inch stereoscope, with careful exclusion of extraneous stimuli and with a slide design demanding focus at the optical equivalent of a finite distance, phoria measures corresponded quite closely with measures at 20 feet (6 meters), distributions of scores by the two methods were similar, correlations between scores by the two methods were reasonably high, and the reliability of the stereoscope tests was reasonably high. Changes due to increased instrument experience had been eliminated in this model. At the other extreme is the hand stereoscope in which phoria measures seemed very erratic and correlated practically zero with those at a true distance." Characteristics of less satisfactory stereoscopes, which are probably responsible for their unsatisfactoriness, are suggested. (PsycInfo Database Record (c) 2025 APA, all rights reserved)