A canine model of inherited myopia: Familial aggregation of refractive error in Labra

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A canine model of inherited myopia: Familial aggregation of refractive error in Labrador Retrievers. Invest Ophthalmol Vis Sci. 2008 Jun 19; Authors: Black JM, Browning SR, Collins AV, Phillips JR Purpose: To determine whether the distribution of naturally occurring myopia in Labrador Retrievers has a genetic component. Methods: Pedigree records were analyzed for a large canine family. Pure Labrador Retrievers, 1-8 years of age, free of ocular pathology and available for testing, were studied. Refractive error was measured by cycloplegic retinoscopy in both eyes. The family included mating loops, so an expectation maximization (EM) algorithm (multivar program, MORGAN software) was used to calculate log-likelihoods of refractive error with environmental and additive genetic models. The fixed effects of coat color, gender and litter size were also tested. Results: In our sample of 116 dogs from this one family, the average spherical equivalent refraction (SER) was -0.41D (range -5.38D to +1.65D, mean of both eyes, n = 116): 31% were myopic (SER /= +1.00D). The significance of fixed and genetic effects was tested by comparing the full model (including genetic and all fixed effects) to models with one effect removed. Litter size and additive genetic effects were significant (p = 0.0013 and p = 0.000093 respectively), while gender and coat color were not. The overall variance in SER was accounted for approximately equally by additive genetic variance and residual/environmental variance. Narrow sense heritability of SER was 0.506. Conclusion: The distribution of refractive error within this family of Labrador Retrievers had a significant genetic component, but was also influenced by other factors (litter size, and undefined residual/environmental effects). The dog represents a unique model for the study of naturally occurring, heritable, high prevalence, low degree myopia. PMID: 18566472 [PubMed - as supplied by publisher]

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