Objective - To assess the refractive state of eyes in various breeds of dogs to identify breeds susceptible to ametropias. Animals - 1,440 dogs representing 90 breeds. Procedures - In each dog, 1 drop of 1% cyclopentolate or 1% tropicamide was applied to each eye, and a Canine Eye Registration Foundation examination was performed. Approximately 30 minutes after drops were administered, the refractive state of each eye was assessed via streak retinoscopy. Dogs were considered ametropic (myopic or hyperopic) when the mean refractive state (the resting focus of the eye at rest relative to visual infinity) exceeded ± 0.5 diopter (D). Anisometropia was diagnosed when the refractive error of each eye in a pair differed by > 1 D. Results - Mean ± SD refractive state of all eyes examined was -0.05 ± 1.36 D (emmetropia). Breeds in which the mean refractive state was myopic (≤-0.5D) included Rottweiler, Collie, Miniature Schnauzer, and Toy Poodle. Degree of myopia increased with increasing age across all breeds. Breeds in which the mean refractive state was hyperopic (≥+0.5 D) included Australian Shepherd, Alaskan Malamute, and Bouvier des Flandres. Astigmatism was detected in 1% (14/1,440) of adult (≥ 1 year of age) dogs; prevalence of astigmatism among German Shepherd Dogs was 3.3% (3/90). Anisometropia was detected in 6% (87/ 1,440) of all dogs and in 8.9% (8/90) of German Shepherd Dogs. Conclusions and Clinical Relevance - Refractive states of canine eyes varied widely and were influenced by breed and age. In dogs expected to have high visual function (eg, performance dogs, determination of refractive state is recommended prior to intensive training.
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