Age‐Related Pupillary Margin Atrophy in Dogs: Quantification, Topographic Distribution, and Possible Pathophysiologic Implications

PURPOSE: To characterize changes to the pupillary margin in dogs of different ages. METHODS: The pupillary margin was scored for morphologic changes in normal eyes of dogs < 3.5 years and of dogs > 9.5 years of age. The pupillary margin was divided in eight sectors, with each sector scored qualitatively and quantitatively in four grades, from normal to entropion uveae. RESULTS: Four-hundred and nine eyes from 243 dogs were included. One-hundred forty-one eyes from 75 dogs < 3.5 years were scored. The averaged score was 0.07 OD and 0.09 OS. None of the dogs < 1.5 years had visible changes. Two-hundred and sixty-eight eyes from 168 dogs > 9.5 years were scored. All eyes were affected. The average score was 3.83 OD and 3.89 OS. The inferior-temporal quadrant was the most affected in both groups. Older dogs had significantly higher scores of iris atrophy (p < 0.001). CONCLUSIONS: Atrophic changes of the pupillary margin occur in all dogs with age, starting at 16 months in the population observed and are significantly more severe in older patients. This study provides an initial quantitative and qualitative scoring system to guide future work. Iridal changes likely result from biophysical interaction between the pupillary margin and the lens. The advanced changes may represent homeostatic responses to tissue damage. The missing tissue and its released molecules may constitute a chronic trigger for innate immunity. Pupillary margin changes may represent indicators of risk factors for the pathogenesis of age-related clinical conditions in breeds with genetic predispositions.