Visual field defects in esotropic cats: a developmental consequence of the squint.

In nine adult cats with surgically induced esotropia (squint-angle ranging between 8 degrees and 32 degrees), the extent of binocular and monocular visual fields was behaviourally assessed by the food-perimetry method. Results indicate that: (1) The extention of both the nasal and the temporal hemifield of the esotropic eye is narrowed. (2) Field losses are largest in the cats with severe esotropia (> 15 degrees); yet the relationship between rate of impairment scored in each animal and individual angles of squint is not linear. (3) In the cats with severe esotropia, the visual field of the non-deviated eye is also narrowed. (4) We suggest that field deficits reflect a stop in the developmental expansion of the immature visual field as a consequence of ocular misalignment.