The effect of a topical antioxidant formulation including N-acetyl carnosine on canine cataract: a preliminary study

To determine the efficacy of a topical antioxidant formulation including N-acetyl carnosine in the treatment of canine cataract in a preliminary nonplacebo, controlled, unmasked study. Thirty dogs of varying breeds and ages with a spectrum of lens opacities ranging from nuclear sclerosis to total mature cataract. Dogs were treated three times daily with topical 2% N-acetyl carnosine in a buffered vehicle containing the antioxidants glutathione, cysteine ascorbate, [smallcapital l]-taurine and riboflavin (Ocluvet[trade mark sign], Practivet, Phoenix, AZ, USA). Dogs were examined prior to treatment and at 2, 4 and 8 weeks during treatment, by direct and indirect ophthalmoscopy and slit-lamp biomicroscopy after pharmacologic pupil dilation. Photographic documentation of lens opacity was achieved by retroillumination photography, with three photographs taken at each examination time-point. A lens opacification index (LOI), determined by integration of the grayscale level of each pixel across the image, was evaluated by computerized image analysis of digitized images. Alteration in mean LOI was determined for each animal, having normalized the initial LOI. Fifty-eight eyes of 30 dogs were evaluated, 22 with mature cataract, 13 with immature cataract, 9 with cataract associated with other intraocular disease such as uveitis and 14 with nuclear sclerosis alone. One dog was unilaterally anophthalmic after previous enucleation and one had a phthytic eye after previous uveitis-induced glaucoma. Image analysis showed a reduction in mean LOI in all cataract groups (mean resolution in opacity of 2.3 ± 0.33% for all cataracts), although this was only statistically significant in those eyes with immature cataract (mean resolution of opacity 4.5 ± 0.33%) or nuclear sclerosis (mean decrease in opacity 5 ± 0.37%). Reduction in lens opacity was seen in eyes with mature cataract (0.5 ± 0.4%) and in miscellaneous cataract associated with intraocular inflammation (1.3 ± 0.4%), but these changes were not statistically significant. Owner evaluation of visual capability, however, suggested improvement in vision in 80% of cases by the end of the study. This study demonstrates some marginal reduction in lens opacification in a substantial number of cases of canine cataract with the use of a topical nutritional antioxidant formulation including N-acetyl carnosine. Lens opacification was improved with treatment in eyes with immature cataract or nuclear sclerosis while in eyes with mature cataract or cataract with associated intraocular inflammatory pathology less reduction was seen.