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P.F. Kador, D.M. Betts, M. Wyman, K. Blessing, J. Randazzo; Amelioration of Sugar Cataracts in Dogs . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4702.
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Purpose: In the United States, the companion pet population includes over 62 million dogs of which nearly 1 in 160 dogs are estimated to be diabetic. Diabetic dogs rapidly form bilateral sugar cataracts which result in vision loss. This generally occurs within 5–6 months from the time of diagnosis. It has been established that sugar cataracts in dogs are osmotic in nature and initiated by aldose reductase. The purpose of this study was to determine whether topical administration of a novel aldose reductase inhibitor formulation can ameliorate canine sugar cataract formation. Methods: Ten 6–month old beagles were fed a diet containing 30% galactose for a period of 7 months to induce sugar cataract formation. Six dogs were topically administered drug twice daily while 4 dogs were only administered vehicle. Cataract formation was monitored at ca. 4 week intervals by portable slit lamp and lens changes were documented by portable fundus photography at 0, 3.5 and 7 months. At the termination of the study, all lenses were removed and analysed for opacity formation, galactitol levels, and drug levels. Results: All vehicle–treated dogs formed cataracts with mature to hypermature bilateral cataracts present after 7 months of galactose–feeding. In the topically drug treated dogs, the initial drug formulation had no effect on arresting either the initiation or progression of sugar cataracts and no difference between the vehicle and treated dogs was apparent after 4.5 months of treatment. Tapetal reflex was absent in the majority of dogs indicating lens opacities were sufficient to block light from reaching the retina. After approximately 4.5 months of galactose feeding, a new formulation, Kinostat, was applied. This resulted not only in a significant arrest of further cataract formation, but also, in a partial reversal of lens opacities and the restoration of tapetal reflex. Conclusions: Topical adminstration of a novel aldose reductase inhibitor formulation, Kinostat, not only arrests the progression of sugar cataracts but also reduces the density of early cortical cataracts. This suggests that functional vision can be restored in dogs with early stages of cataract.
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