It is true that some of the mutations in the CYP1B1 gene - the gene most implicated in PCG - are responsible for JOAG,9 and PCG is reported to have variable expressivity and penetrance.10, 11 This may explain the difference between the fellow eyes and the controls, hypothesizing that these fellow eyes represent arrested or abortive forms of PCG. This evidence concerns the gene CYP1B1 and juvenile open angle glaucoma.