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S. Fan, C.B. Toris, K.A. Blessing, J. Randazzo, P.F. Kador; Correlation Between Aqueous Flow and Sugar Cataract Formation in Galactose–Fed Dogs . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3677.
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Purpose: Dogs fed galactose develop diabetic–like ocular complications that include cataracts, retinopathy, and changes in aqueous flow. Previously, we have observed that aqueous flow is decreased in dogs fed galactose–diet for 36 or more months. (Lane et al, Invest. Ophthalmol Vis Sci. 43(4), 2002). The purpose of this study was to investigate 1) whether aqueous flow is altered by only 7 months of galactose feeding and 2) determine whether inhibition of aldose reductase can affect aqueous flow in these dogs. Methods: Ten 6–month old male beagles were fed a diet containing 30% galactose for 7 months. Six of these dogs also received a twice–daily topical formulation of the aldose reductase inhibitor Kinostat (ARI) while the remaining 4 dogs received vehicle. After 7 months of galactose feeding intraocular pressure (IOP) was measured by Tonopen, aqueous flow by fluorophotometry, cornea thickness by ultrasound pachymetry and anterior chamber (AC) depth by A–scan biometry. Within three days of the fluorophotometry study, all eyes were enucleated and the extent of lens opacity evaluated by densitometry measurements. Results: Previously, we have observed that aqueous flow is significantly reduced (p=.03) in dogs fed galactose for > 3 years (3.1±1.3 µl/min; mean ± S.D) compared to healthy, age–matched control dogs (5.1±1.6 µl/min). IOPs were normal in both groups (14.1±3.4 and 13.5±4.8 mmHg, respectively). Dogs fed galactose for 7 months had normal aqueous flow rates (5.6 ± 1.9 µl/min) and IOPs (15.8 ± 3.0 mmHg) and developed cataracts. Similarly, Kinostat–treated dogs did not differ in either aqueous flow (5.6±2.6 µl/min) or IOP (18.5±2.9 mmHg). However, all galactose–fed dogs topically treated with Kinostat showed less dense cataract formation than those treated with vehicle. By comparing cataract density with observed flow rates in each individual dog, a significant (p=0.03) correlation between aqueous flow rate and density of cataract was observed (r2=0.19, p=0.03). Conclusions: A significant reduction in aqueous flow in dogs requires longer than 7 months of galactose feeding. The observed relationship between decreased aqueous flow and increased cataract formation suggests that inhibition of aldose reductase may play a role. Further studies are required to substantiate this finding.
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