Dr. Carl Hartman, ophthalmologist, gives a brief overview of the two largest categories of glaucoma: Open angle and closed angle glaucoma. While there are many subtypes, these are the most common major groups. It is imperative that each patient with glaucoma be examined by a specialist in order to determine what type of glaucoma they have. Why is this important? Because each type is treated differently and good control may be dependent on the diagnosis being accurate.