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 ClinicalRelevance-A 3.6-m-long obstacle-avoidance course with 6 movable obstacle panels allowed identification of achromatopsic dogs at ambient light intensities ≥ 25 lux based on transit times. This test could be helpful in the evaluation of new cone photoreceptorspecific treatments.The clinical, psychophysical evaluation of visual performance is generally less sophisticated in because of limitations in the assessment of responses to visual stimuli by an untrained animal. The testing of general visual performance in dogs is usually limited to rather simple methods such as the menace response test, the visual placing reaction, and the tracking of objects such as a cotton ball or laser pointer. 1,2 In a clinical setting, dogs may be observed maneuvering around obstacles under different, often ill-defined, ambient light intensities in the examination

Exclusion ofRPGRIP1ins44 from Primary Causal Association with Early-Onset Cone–Rod Dystrophy in Dogs

“…Note that dogs with achromatopsia and total absence of cone function due to CNGB3 mutations have significant increases in obstacle course transit times at the 65 and 646 lux intensities, which are reversed to normal following corrective gene therapy. 18,19 Retinal Histopathology. To determine if cRPGRIP1…”

“…Details of the apparatus and method of testing have been described; the testing modality permits quantitative detection of absent photopic vision in dogs with achromatopsia, and the recovery of cone function following gene therapy. 18,19 The luminance used for testing has now been expanded to lower light levels, and vision is tested at 0.003, 0.2, 1, 65, and 646 lux.…”

Drug and gene therapy of hereditary retinal disease in dog and cat models

“…Behavioral testing of vision is readily performed in dogs and methods have been developed to repeatably quantify visual performance [1][2][3]. Such quantitative assessments of vision are an important part of outcome measures of treatments for retinal dystrophies.…”