Distortion of the image by ophthalmic prisms.

Abstract

THAT THE image seen through an ophthalmic prism is distorted is well known to every refractionist, and this distortion is especially apparent through large prisms, and even through the usual Risley rotary prisms. Although known qualitatively, a general quantitative discussion of this distortion has never appeared in the literature. This situation can be accounted for not only because of the mathematical complications involved but also, and probably more so, because of the general lack of interest in such distortion, except as a phenomenon to be tolerated. In 1927 Hartinger1calculated the magnitude of this distortion for particular prisms with plane surfaces, especially those of high deviating power. He did not give a quantitative description that was applicable to ophthalmic prisms in general. There has been more interest of late in this distortion because of its influence on stereoscopic spatial localization when ophthalmic prisms are worn before the two eyes.