Optotype recognition visual acuity in the domestic cat

Author(s): Daria L.Clark, Robert A.Clark

Behavioral studies estimate feline vision between 3 and 9 cycles per degree (20/67 to 20/200). To determine cat visual acuity using a directly comparable, human optotype recognition task, four cats were trained on a pseudorandom, two-choice discrimination task using HOTV optotypes. The minimum resolvable optotype was then determined by sequentially presenting smaller optotypes at longer distances. The smallest optotype and longest distance successfully completed were confirmed with a second test requiring a minimum27 correct out of 36 consecutive trials, yielding a binomial probability greater than 0.001 of non-randomoccurrence. Two of the four cats completed all training and visual acuity testing: M1, a 6.5 year old male gray tabby with +2.00 OU refraction, tested for best visual acuity of 20/74 and F1, a 1.5 year old female gray tabby with +0.25 OU refraction, tested for best visual acuity of 20/33. These results demonstrate that a young cat with good focus is capable of recognition visual acuity of 20/33, in close agreement to the physiologic maximum. Older age and uncorrected focusing errors can degrade visual performance. Good lighting, high contrast targets, long viewing distances, and lack of time pressure resulted in better feline visual acuity measurements than previously described.

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