Nasal field loss in cats reared with convergent squint: behavioural studies.

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Abstract
The extent of the monocular visual field in cats reared with convergent squint in one eye was determined by a behavioral perimetry technique. Significant reduction in the extent of the visual field was found in the squinting eyes. The visual field defect was a graded one, located mainly in the nasal field, but in some cats extending into the temporal visual field. The defect included a zone of absolute loss of response to stimuli at the extreme nasal field, adjacent areas of partial response and areas of 100% response in the periphery of the temporal field. A direct relationship was found between the angle of horizontal deviation of the squinting eye and the amount of visual field loss: i.e., the larger the angle of squint, the greater the loss of nasal field. The process leading to a loss in nasal visual field may be independent of the loss of visual acuity in squinting cats, since the latter is not related to the angle of squint. The significant loss in nasal visual field found by behavioral experiments in cats reared with a convergent squint correlated with comparable deficits found in the physiology and morphology of the lateral geniculate nucleus [LGN], although the behaviorally determined loss of nasal field was greater than would be expected from the study of the response of the LGN neurons.