Surgery is typically the primary treatment for restoration of cataract-associated vision loss in dogs; however, a medical treatment to preserve vision in diabetic dogs would be beneficial. A randomized, prospective, double-masked, placebo-controlled pilot study was conducted in 40 dogs with newly diagnosed diabetes mellitus (DM) with minimal or no lens changes to assess whether topical administration of the aldose reductase inhibitor (ARI) Kinostat ameliorated the onset or progression of cataracts. All patients were managed with chronic insulin therapy under the guidance of the diagnosing veterinarian. Complete ophthalmic examinations were performed on dilated eyes at the time of enrollment and at 1, 2, 3, 6, and 12 months into treatment. Complete ophthalmic examination included a Schirmer’s tear test (STT), intraocular pressure (IOP) measurement, biomicroscopy, and indirect ophthalmoscopy. Lens changes were subjectively graded on a scale of 0 to 3, with 3 representing late-stage cataracts. Dogs with normal STT, normal IOP, no lens opacities, or only equatorial vacuoles were included in the study. Kinostat was administered to 28 dogs and placebo to 12 dogs; owners administered the agent into both eyes Q 8 H for 1 year. The cataract score in the placebo group significantly increased after 12 months of treatment; 7 dogs developed mature cataracts, 2 dogs developed cortical opacities, and 1 dog developed equatorial vacuoles with mild punctate cortical opacities. The cataract score in the Kinostat-treated dogs was significantly lower with 7 developing anterior equatorial vacuoles, 2 developing incipient anterior cortical cataracts, and 4 developing mature cataracts. Glycosylated hemoglobin concentration (HbA1C) values between both groups were similar after 12 months, and blood levels of Kinostat were not detected in any enrolled dog. The development and severity of cataracts were significantly less in Kinostat-treated dogs, suggesting that topical Kinostat is clinically beneficial in arresting the onset and/or progression of cataracts in dogs with DM. The use of Kinostat may be warranted in dogs with mild lens changes, but may not significantly impact more advanced lens changes.

Commentary: Data from this exciting study suggest that Kinostat may be clinically useful in diabetic dogs with early and mild lens changes and may delay onset or progression of associated cataracts. The potential preservation of vision is an attractive and superior alternative to surgical solutions in diabetic dogs. This is a pilot study with small sample sizes. Future trials should evaluate larger cohorts of diabetic dogs and cataract progression.—Indu Mani, DVM, DSc

Topical Kinostat ameliorates the clinical development and progression of cataracts in dogs with diabetes mellitus. Kador PF, Webb TR, Bras D, et al. VET OPHTHALMOL 13:363-368, 2010.