Glaucoma is caused by high liquid pressure inside the eye that causes damage to the optic nerve. A blocked drainage canal in the cornea near the front of the eye can cause too much fluid to stay in the eye, putting pressure on the back of the eye where the optic nerve connects. The most common form, open-angle glaucoma, generally appears in middle age and seems to have a genetic component. Those with a family history of glaucoma, with African or Hispanic ancestry, or with diabetes are at a higher risk. Vision loss occurs very gradually and is often worse in one eye than the other. Regular eye exams can catch the early symptoms of glaucoma and with treatment can drastically slow the progression of glaucoma.