One of the primary risk factors for glaucoma is family history. Therefore, a genetic predisposition to glaucoma that runs in families is common. How glaucoma presents within a family, however, is quite variable among different individuals. How a particular trait or gene presents within different members of a family is called expression. The genetic predisposition to glaucoma can be expressed differently in different individuals. Generally, the younger the age at which glaucoma presents, the higher the eye pressure and the more difficult it is to treat compared to older individuals. If your family has a strong genetic predisposition to glaucoma, it is important for everyone to be sure they see an eye doctor early in life and then be checked regularly.