MYOC and glaucoma: As only the coding region of CYP1B1 was sequenced, we thought that it might be due to mutations in (1) the CYP1B1 promoter or other non-coding regions; (2) genes linked to other PCG loci, such as GLC3B and GLC3C; (3) other glaucoma genes such as MYOC, resulting in digenic inheritance; or (4) some other unknown genes causing glaucoma.