Association of SIX1/SIX6 locus polymorphisms with regional circumpapillary retinal nerve fibre layer thickness: The Nagahama study

SIX1 and SIX6 are glaucoma susceptibility genes. Previous reports indicate that the single nucleotide polymorphism (SNP) rs33912345 in SIX6 is associated with inferior circumpapillary retinal nerve fibre layer (cpRNFL) thickness (cpRNFLT). Although the region of visual field defect in glaucoma patients is directly related to cpRNFL thinning, a detailed sector analysis has not been performed in genetic association studies. In the present study, we evaluated 26 tagging SNPs in the SIX1/SIX6 locus ±50 kb region in a population of 2,306 Japanese subjects with 4- and 32-sector cpRNFLT analysis. While no SNPs showed a significant association with cpRNFLT in the 4-sectored analysis, the finer 32-sector assessment clearly showed a significant association between rs33912345 in the SIX1/SIX6 locus with inferior cpRNFL thinning at 292.5–303.8° (β = −4.55, P = 3.0 × 10(−5)). Furthermore, the fine-sectored cpRNFLT analysis indicated that SIX1/SIX6 polymorphisms would affect cpRNFL thinning at 281.3–303.8°, which corresponds to parafoveal scotoma in a visual field test of glaucoma patients.