Visual field defects in monocularly and binocularly deprived cats

Abstract

(1) A perimetry test was used to measure the visual responsiveness of discrete regions in the visual field of 2 normal, 4 monocularly deprived (MD) and 2 binocularly deprived (BD) cats. One of the MD cats as an adult underwent a reverse suture operation which forced it to use its formerly deprived eye for a 9 month period. Except for this MD cat which was tested only with its formerly deprived eye, each cat was tested binocularly and monocularly with each eye. (2) In agreement with previous results, normal cats responded binocularly to objects presented anywhere in the region bounded approximately from 100° right-lateral to 100° left-lateral. The monocular visual fields were measured to be approximately from 100° ipsilateral (to the open eye) to 45° contralateral. Thus the binocular segment of visual field includes the region bounded bilaterally by about 45°, and the monocular segment of each side is bounded approximately between 45° and 100°. (3) Each of the 3 MD cats tested with both eyes showed a normal monocular visual field for the non-deprived eye. Each with the deprived eye, however, ignored objects presented in the binocular segment yet, after a period following eye-opening, responded fairly normally to objects presented in the monocular segment. Binocularly, the visual fields of these cats appeared fairly normal. This response pattern was evident during the first testing after opening of the deprived eye although the responses with this eye improved considerably in the ensuing days. (4) The MD cat with reverse suture had a monocular visual field for its formerly deprived eye which closely matched the deprived eye fields of the other 3 MD cats. The reverse suture procedure resulted in no qualitative improvement for the formerly deprived eye. (5) Each BD cat had a fairly normal binocular visual field. When tested monocularly, however, they consistently ignored stimuli presented in the hemifield contralateral to the open eye. Unlike the MD cats, no visual responses were seen in the BD cats for several days after eye-opening. (6) The behavior of MD cats is suggested to be related to physiological deficits which are limited to the binocular segment of the geniculostriate system, and perhaps also to this segment of the superior colliculus. It is further suggested that the behavior of BD cats results from a cortex which is non-functional for visually guided behavior and a superior colliculus which controls this behavior but which receives functional visual afferents almost exclusively from the contraleteral retina.