Glaucoma is common eye disease in older patients in which the optic nerve of the eye is damaged, resulting in vision loss. There are two main forms of glaucoma: open angle glaucoma and angle closure glaucoma. Open angle glaucoma is the most common form of glaucoma and it often goes undetected in the early stages. The reason it goes undetected is that it is painless so a person does not realize that they are slowly losing the ability to see until it has become too severe. That is why it is important to have regular eye exams to check for disease such as glaucoma that can slowly become more damaging over time. The other main form of glaucoma is called angle closure glaucoma. This much less common than open angle glaucoma but it can also cause damage to the optic nerve, sometimes much more rapidly and in a painful fashion that is noticeable to the patient.