CYP1B1 and juvenile open angle glaucoma: Homozygous mutations in CYP1B1 were assessed to be the cause of JOAG in 4 of the 23 probands (17.4%) screened, the same number as those whose disease was caused by MYOC. Mutations in MYOC were not observed in any of these four patients, and none of the individuals in our cohort were observed to carry only a single mutated CYP1B1 allele.