SIX1 and open-angle glaucoma: Given 1) the observed association signal pattern; 2) the lack of coding changes identified in SIX1; 3) the presence of rare missense variants and a common, associated missense SNP in SIX6; 4) retinal nerve fiber layer thickness changes observed in POAG cases homozygous for the SIX6 risk allele; and 5) the localized expression of SIX6 in ocular tissues, we concluded SIX6 is a likely candidate gene in this region.