A relationship between visual suppression and amblyopia in cats with cyclodeviations of the eyes

Visual pattern and brightness discriminations were tested in cats which had undergone surgical cyclodeviations of one or both eyes. Half of the pattern discriminations were learned with both eyes open and performance was tested with each eye separately; the other half were learned monocularly with the normal eye (in cats with monocular rotations, MR) or with the less amblyopic eye (in cats with binocular rotations, BR) and then the rotated (or amblyopic) eye was tested alone. No deficits were found in brightness discriminations. With monocularly learned pattern discriminations all but one cat showed positive savings when tested with the rotated eye. However, on binocularly learned discriminations half of the animals performed poorly with the rotated eye and required extensive retraining; they showed negative savings when compared to original learning. These animals seem to be suppressing the strabismic eye during binocular vision. For MR cats, there was a positive relationship between visual acuity and percent savings after binocular learning. The relationship between amblyopia and suppression suggests a common cause.