Quantitative measurement of stereopsis by liquid crystal phase difference haploscope
Kawamura, M.; Yazawa, K.; Hirano, A.; Kato, K.
Nippon Ganka Gakkai Zasshi 85(6): 548-555
1981
ISSN/ISBN: 0029-0203 PMID: 7293868 Document Number: 168882
Liquid crystal phase difference haploscope dissociates 2 eyes by liquid crystal glasses which can be alternately clear and cloudy by an electric control and works as a shutter; this can differentiate the 2 visual fields completely. The projected image from the right projector is seen only by the right eye and the image from the left projector falls on the left eye only. The 2 images are seen continuously by each eye when projected at a speed above 25 Hz. A pair of stereoscopic slides were projected on the screen with the temporal disparity producing a sense of nearness at a distance of 2 meters. Pallalax of 360 s of arc, which corresponds to 3.5 mm displacement on the screen, was the minimum needed to produce a sense of stereoscopic depth. The nearer the stereoscopic image, the smaller was the image corresponding to the visual angle. Relationship between the pallalax and the stereoscopic depth was calculated and a normal theoretical value was made. A measurement of stereoscopic depth in normal population showed a good correlation with the theoretical value. Exophoria and accommodative esotropia group showed a marked decrease and instability in stereoscopic depth as a displacement of the 2 projected images became larger. Stereopsis on the synoptophore was compared to that of the liquid crystal haploscope utilizing the same stereoscopic slides. Most of the patients with inadequate stereoscopic depth on the liquid crystal haploscope showed slow response on the synoptophore or error in stereopsis especially when the 2 slides were exchanged from temporal disparity to nasal disparity or vice versa. Liquid crystal phase difference haploscope was useful clinically in a quantitative measurement of stereopsis.