In this study, we also subdivided the POAG subjects into two subtypes based on the IOP level measurements in an attempt to discover subtype-specific variants, which would be useful for investigating the different mechanism of each pathogenesis. Since the clinical states of both subtypes overlap almost completely, they are usually categorized as a single disease. However, as a unique epidemiological distribution compared with other ethnic groups, ,92% of the Japanese POAG patients fall into the NPG category, as determined by the Tajimi study [4] , a robust epidemiology study. In fact, another Japanese group performed a GWAS focused on discovering NPG-specific variants [12] . They reported that the SNPs in SRBD1 on 7q31.1 and ELOVL5 on 6p12.1 were associated with NPG, although our group was unable to replicate those results ( Figure S5D, E) . On the contrary, we obtained an unexpected result that the variants associated with NPG were completely identical to those associated with POAG in CDKN2B-AS1 identified in this study (Table S1 ). In contrast, none of the variants were significant for HPG ( Figure 3B ). Although we cannot rule out that the significance could be due to the differences in sample size between HPG and NPG cases according to the heterogeneity test (P = 0.21-0.25; Table S3 ), the results suggested that the genetic loci identified are most likely components of the molecular mechanism specific for NPG. It has been reported that there are differences in vulnerability of the optic nerve to IOP between HPG and NPG [18] . It has also been theorized that CDKN2B-AS1 affects the susceptibility of the optic nerve [14, 28] . Since the variants identified in this study seemed to be shared among different ethnicities in functional aspects as well, the other variants should be contributing to the unique epidemiology of NPG in Japanese. By continuing to build upon the detailed investigation, such as obtaining in-depth sequencing data of the non-coding 9p21 locus, it might be possible to reveal not only the molecular mechanism of glaucoma pathogenesis but also the genetic diversity that resides within the locus among different ethnic backgrounds.