[Pulfrich phenomenon]

A physiological and clinical study of the Pulfrich stereo-phenomenon was performed. The most important physiological parameters are object movements, luminous factors, and the position and movement of the eyes. Our experimental research emphasizes the retinal illumination factors, modified by many optical devices (pinhole, stenopeic slit, etc.); the paradoxical perceptive aspects of the Pulfrich phenomenon; and, above all, outlines the negligible role of the metric factors. The Pulfrich phenomenon is mainly time-dependent, and is defined as a stereoscopic illusion related to the temporal disparity between the visual input arising from the two eyes at the time of their cortical integration. In ocular pathology, 267 subjects were studied, the ocular abnormalities being divided into diseases of the pupil, cornea and vitreous body, cataracts, retina, optic nerve, glaucoma and strabismus. The difference between the spontaneous Pulfrich phenomenon and the provoked Pulfrich phenomenon is stressed: the spontaneous Pulfrich phenomenon is rare (14% of subjects); by itself it is anomalous and is a functional symptom his mechanism may vary according to the etiology; on the contrary, the provoked Pulfrich phenomenon is a normal phenomenon, induced by a filter in front of one eye; its absence is pathological either with the filter in front of the better eye, the bad eye, or of each in turn. In clinical practice this lack is frequent (46% of subjects), and is related to an alteration of binocular vision, but without etiological specificity.