1. The visual field in each eye of five kittens raised with a unilateral surgical strabimus (three esotropes, two exotropes) was measured, using a method of unreinforced visual orienting. Three normal kittens matched for age (2 1/2-3 months) served as controls. 2. Normal kittens oriented briskly towards visual stimuli presented anywhere from 105 deg temporal to 60 deg nasal, with the more peripheral stimuli being progressively less effective (overall level of responsiveness: 86%). They oriented about 12% of the time towards "blank" stimuli. 3. The orienting responses evoked through the nonoperated eye of the strabismic kittens were definitely abnormal: all kittens showed a clear nasal field loss and some a temporal field loss as well. Visual responsiveness varied between 61 and 67%. 4. The orienting responses were dramatically impaired when the operated eye was tested alone: the level of responsiveness varied between 31 and 50%, and there was a dramatic shrinkage of the effective visual field, both nasally and temporally. 5. These results were independent of the direction of the eye deviation. All kittens used exclusively their nonoperated eye for fixation. 6. The deficits seen in this study were much greater than those obtained previously by food perimetry. 7. The deeper functional loss of the deviated eye, and the bilateral loss of responsiveness in the nasal visual field correlate better with single-cell properties in the extrastriate visual cortex (lateral suprasylvian area) than with cell properties in area 17.
