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Lauren Elizabeth Gillespie, Rebecca E.H. Whiting, Haley N Lewis, Leilani J Castaner, Martin L. Katz; Novel method for evaluating functional vision in a canine model of CLN2 neuronal ceroid lipofuscinosis. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2769.
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© ARVO (1962-2015); The Authors (2016-present)
While some methods used to evaluate the visual system in people are also applicable to dogs, a method is needed to objectively assess canine functional vision in order to better translate potential treatments for visual defects from dogs to people. CLN2 disease is a fatal genetic disorder in children characterized by gradual vision loss and neurological decline. Dogs with CLN2 disease exhibit similar disease signs. Several options for treating vision loss associated with CLN2 disease are currently under investigation. A technique was developed to assess functional vision in normal and CLN2-affected dogs.
Normal Dachshunds (n=7), between 3 and 20 months of age, were trained to touch the nose to one of two differently-shaped white objects on black backgrounds, with each object displayed on one of two Apple iPad® tablets. Standard canine positive reinforcement training techniques were used to shape behavior. Training required 15 minutes per weekday for 6-7 weeks. Thereafter, monthly testing required daily sessions for 1 week. Each testing session consisted of the dog choosing between two images, with the location of the correct image changing between the two iPads in a predetermined, random sequence. Test sessions were repeated until the dog passed a phase by making a minimum number of correct choices. Performance was scored as the number of sessions required to reach passing criterion. For each subsequent phase, object size decreased by 50% from the previous phase. Object size was reduced until correct responses fell to chance on 20 consecutive trials.
The number of testing sessions required to pass a phase increased as object size decreased. After sufficient training, normal Dachshunds were able to consistently distinguish 25 mm tall objects and larger. Some dogs were also able to distinguish 12.5 mm tall objects. Studies are ongoing to evaluate functional vision of CLN2-affected dogs as the disease progresses.
Methods for evaluating functional vision in dogs provide a useful technique for assessing treatment efficacy in canine models of visual disease and in translating therapies from research dogs to people. In particular, these methods will aid in assessing treatment efficacy of ongoing trials in dogs with CLN2 disease.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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