How can I have glaucoma; is it age-related or is it hereditary?

Any one can develop. glaucoma. Though there is a hereditary component to it, it is not 100% dominant, meaning it can skip generations. Also it can also start randomly with you. Since glaucoma is so asymptomatic in its early stages, many people can die without knowing that they ever had the disease and family members will never know. Also some may have, but haven't spoken out. Best thing to do is keep up with treatment.
It's in the genes. Glaucoma is an inherited disease. You inherit a gene from each parent. Glaucoma, while more common in older people, can begin at any age. This is why the test for glaucoma is part of a routine eye examination. The overall chance of having glaucoma is about 3% in the general population and has nothing to do with diet or weight.