Glaucoma is not contagious and cannot be transmitted from person to person by contact or any other mode of transmission, such as saliva, blood, or sexual transmission. If a family member or someone close to you has glaucoma, you can't get it at all.
Glaucoma may have an inherited component. If you have relatives with glaucoma, you are more likely to develop it than the general population because of the genetic component. Even if your parents have glaucoma, you don't have to develop it too, but it's a good idea to do some preventive screening.
Glaucoma causes damage to the optic nerve due to increased intraocular pressure that is often permanent if the disease is not treated early. Early treatments can stop the disease.