PURPOSE: To determine whether the distribution of naturally occurring myopia in Labrador Retrievers has a genetic component. METHODS: Pedigree records of a large canine family were analyzed. Pure Labrador Retrievers, 1 to 8 years of age, free of ocular disease, and available for testing were studied. Refractive error was measured by cycloplegic retinoscopy in both eyes. The family included mating loops, and so an expectation maximization (EM) algorithm (multivar program, MORGAN software; University of Washington, Seattle) was used to calculate log likelihoods of refractive error with environmental and additive genetic models. The fixed effects of coat color, sex, and litter size were also tested. RESULTS: In our sample of 116 dogs from this one family, the average spherical equivalent refraction (SER) was -0.41 D (range, -5.38 to +1.65 D, mean of both eyes, n = 116): 31% were myopic (SER <or= -0.50 D), 60% were emmetropic (SER = -0.49 to +0.99 D), and 9% were hyperopic (SER >or= +1.00 D). 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), whereas sex 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. CONCLUSIONS: 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.
PURPOSE: To determine whether the distribution of naturally occurring myopia in Labrador Retrievers has a genetic component. METHODS: Pedigree records of a large canine family were analyzed. Pure Labrador Retrievers, 1 to 8 years of age, free of ocular disease, and available for testing were studied. Refractive error was measured by cycloplegic retinoscopy in both eyes. The family included mating loops, and so an expectation maximization (EM) algorithm (multivar program, MORGAN software; University of Washington, Seattle) was used to calculate log likelihoods of refractive error with environmental and additive genetic models. The fixed effects of coat color, sex, and litter size were also tested. RESULTS: In our sample of 116 dogs from this one family, the average spherical equivalent refraction (SER) was -0.41 D (range, -5.38 to +1.65 D, mean of both eyes, n = 116): 31% were myopic (SER <or= -0.50 D), 60% were emmetropic (SER = -0.49 to +0.99 D), and 9% were hyperopic (SER >or= +1.00 D). 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), whereas sex 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. CONCLUSIONS: 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.
Authors: David Troilo; Earl L Smith; Debora L Nickla; Regan Ashby; Andrei V Tkatchenko; Lisa A Ostrin; Timothy J Gawne; Machelle T Pardue; Jody A Summers; Chea-Su Kee; Falk Schroedl; Siegfried Wahl; Lyndon Jones Journal: Invest Ophthalmol Vis Sci Date: 2019-02-28 Impact factor: 4.799
Authors: Allyson D Groth; Steven R Hollingsworth; Ron Ofri; Philip H Kass; Zoe Reed; Christopher J Murphy Journal: Vet Ophthalmol Date: 2012-11-22 Impact factor: 1.644
Authors: Emiliano Bruner; José Manuel de la Cuétara; Michael Masters; Hideki Amano; Naomichi Ogihara Journal: Front Neuroanat Date: 2014-04-02 Impact factor: 3.856