Evaluation of a behavioral method for objective vision testing and identification of achromatopsia in dogs.

Abstract

OBJECTIVE: To develop a quantifiable behavioral test for identification of achromatopsic dogs based on visual performance. ANIMALS: 14 dogs. PROCEDURES: A 3.6-m-long obstacle-avoidance course with 6 obstacle panels was developed from a preliminary 2.4-m-long course. Achromatopsic and visually normal control dogs were run through the course at 4 ambient light intensities (from dim to bright: 0.2, 25, 65, and 646 lux). Completion of 4 runs ranging from dimmest to brightest light intensity constituted 1 complete trial. Each dog underwent 3 trials. Transit times were measured and compared between dog groups and between light intensities by use of a generalized linear model and ANOVA. RESULTS: At the 3 highest light intensities, the achromatopsic dogs needed significantly more time to pass through the obstacle course than the control animals. Compared with the mean transit time at the lowest light intensity, mean transit times were 2.6 times as long at 25 lux, 3.2 times as long at 65 lux, and 5.7 times as long at 646 lux. The achromatopsic dogs had signs of increasing difficulty navigating around the obstacle panels with increasing light intensities; this was not the situation for the control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: A 3.6-m-long obstacle-avoidance course with 6 movable obstacle panels allowed identification of achromatopsic dogs at ambient light intensities >or= 25 lux based on transit times. This test could be helpful in the evaluation of new cone photoreceptor specific treatments.