Glaucoma is a chronic eye disease that progresses slowly over time causing loss of eyesight. There is a buildup of pressure within the eye, because the eye’s drainage system is malfunctioning. A narrowing or complete blockage of the drainage system prevents fluid from flowing out of the eye in a normal fashion. This causes an excessive buildup of pressure within the eye that damages the optic nerve resulting in vision loss. It takes months to years before you notice eye problems, and the vision that has been lost cannot be restored.