Thus, the current study extends the previous findings by: (a) comprehensively covering the gene by genotyping 33 SNPs for GABBR2, (b) increasing our sample size by ∼760 participants, (c) including an association analysis of GABBR1 with ND, and (d) examining the interaction between GABBR1 and GABBR2. Here, GABBR1 is linked to Norrie disease.