The leading cause of blindness. Very important to have ones eyes tested regularly, especially from the age of 40. Early symptoms of glaucoma can be treated to prevent total loss of vision. Experience poor vision (one will think it is part of growing older). Glaucoma is where there is a lot of pressure within the eye. You have a protective fluid called "Aqueous Humour" the space between the front of the lens/clear fluid. This does not drain and causes pressure within the eyeball and is very painful. Glaucoma comes without warning.
Glaucoma Research Foundation