Myopia and refractive error in dogs.

The refractive error of 240 phakic dogs of various breeds was measured using streak retinoscopy and averaged (-0.27 +/- 1.41 D relative to infinity). Analysis by breed showed that the German Shepherd, Rottweiler, and Miniature Schnauzer breeds had an increased prevalence of myopia with an average refractive error of -0.86 +/- 1.31 D, -1.77 +/- 1.84 D, and -0.66 +/- 1.05 D, respectively. Myopia also was found in older dogs with marked nuclear sclerosis of the crystalline lens. Fifty-three percent of all German Shepherd dogs in a veterinary clinic population (n = 58 eyes) had a myopic refraction of greater than or equal to -0.50 D; 64% of all Rottweiler dogs (n = 28 eyes) were myopic. An in-depth investigation of German Shepherd dogs, using A-scan ultrasonography, photokeratoscopy, and streak retinoscopy, was done at Guide Dogs for the Blind (San Rafael, CA). By contrast with the results obtained in the veterinary clinic population, the overall average refractive error of guide dog German Shepherd dogs (n = 106 eyes) was +0.19 +/- 0.81 D, and only 15% of these dogs were myopic. The axial length and corneal curvature of myopic eyes did not differ significantly from nonmyopic eyes.