Glaucoma is a common disorder of the optic nerve. It can be divided into two basic types. Open-angle glaucoma is the most common form, accounting for 90% of all cases. It is associated with aging. When a person ages, the eye's drainage apparatus may not work as effectively as it should. This causes the intraocular pressure to increase gradually, slowly damaging the optic nerve and impairing the visual field. In narrow-angle (or angle-closure) glaucoma, the eye pressure is normal until the drainage angle becomes suddenly blocked. The intraocular pressure rises abruptly to dangerous levels. When this occurs, immediate treatment is necessary to prevent blindness.
Open-angle glaucoma: asymptomatic until late in the disease process when poor peripheral vision becomes apparent; narrow angle (or angle-closure) glaucoma: headache or brow ache after being in a darkened room, blurred vision at night, colored haloes around light, severe eye pain, nausea and vomiting