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Karine Duarte Bojikian, Mark A Slabaugh, Philip P Chen, Jay Neitz, Maureen Neitz; Relationship between cone opsin gene variants and the risk for glaucoma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3813.
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The human long-wavelength (L) and middle-wavelength (M) cone opsin genes (OPN1LW and OPN1MW, respectively) are highly variable. The variation has been shown to have deleterious consequences for photoreceptor function. The high degree of genetic variability in these genes make them candidate risk factors for common inherited blinding diseases such as glaucoma. Here we test the hypothesis that L and M cone photopigments are risk factors for glaucoma.
Two populations were prospectively collected: an unselected population was composed of 418 volunteer male subjects without a history of ocular disease, all of whom were confirmed to have normal color vision; the glaucoma population was composed of 99 subjects, males and females, followed at the University of Washington Eye Institute Glaucoma Clinics with a diagnosis of open angle glaucoma (OAG). Only females homozygous for opsin gene haplotypes were included for the final analysis. Each patient underwent: (1) measurements of the axial length and corneal curvature from which spherical equivalent refraction (SER) was calculated, and (2) collection of blood or saliva for genetic analysis. An opsin gene haplotype was determined for each subject by sequencing the OPN1LW and OPN1MW genes, which encode the long- and middle-wavelength sensitive cone opsins, respectively. For haplotypes found in at least 3% of the control subjects, we compared the fraction of subjects with each haplotype in the glaucoma versus control samples.
A chi-squared analysis revealed a significant difference in the distribution of haplotypes in the glaucoma versus control samples (p=0.0126) (Figure 1), suggesting a role for cone opsin haplotype in glaucoma.
The high degree of variability observed among the human L and M opsins make them excellent candidates for common complex diseases, such as glaucoma. These results suggest that the L and M opsin haplotypes are significantly associated with glaucoma. A possible mechanism is that chronic differences in response characteristics between adjacent cones expressing different opsin variants may stress the ganglion cells by increasing their average activity, contributing to loss in viability.
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