Summary
In two dark reared, 40 day old kittens unilateral divergent squint was induced be resecting the insertion of the medial rectus muscle. Behavioural testing revealed that the kittens used only the normal eye for fixation. Contrast sensitivity functions of the two eyes and visual acuity were determined behaviourally in a jumping stand whereby the kittens had to discriminate sine-wave gratings or variable spatial frequency and contrast from a flux equated homogeneous field. At photopic luminance levels the deviated eye showed a significant deficit in both kittens. This impairment was apparent over the whole range of spatial frequencies (0.18–0.99 c/deg) except for the lowest spatial frequency in one kitten. The interocular difference of visual acuity disappeared at scotopic luminance levels. In subsequent electrophysiological experiments contrast sensitivity functions were determined from cortical evoked potentials that were elicited by phase reversing square wave gratings. Comparison between behavioural and electrophysiological results revealed a very good correspondence between the two sets of data. It is concluded that exotropia without alternating fixation leads to functional amblyopia of the deviated eye.
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This study was partially supported by a grant from the Deutsche Forschungsgemeinschaft, SFB 50, Kybernetik
Parts of this study were presented at the Meeting of the Physiological Society in Cambridge, England, June 1978, and at the ARVO Meeting in Sarasota, FL, USA, 1979
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von Grünau, M.W., Singer, W. Functional amblyopia in kittens with unilateral exotropia. Exp Brain Res 40, 305–310 (1980). https://doi.org/10.1007/BF00237795
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DOI: https://doi.org/10.1007/BF00237795