About 1 person in every 50, over the age of 40, has glaucoma.  People with a family history of glaucoma are at greater risk of developing the condition, as are Afro-Caribeans and those who are very short sighted.  Just because your grandmother has glaucoma does not mean that you will also develop the condition, but it is important to have regular eye examinations, particularly as you get older, to identify any problems, should they occur, at an early stage.