Glaucoma is a group of disorders that affects the eye, leading to damage to the ganglion cells and their axons. This results in irreversible damage to the optic nerve. Glaucoma represents one of the leading causes of irreversible blindness in the USA and world-wide. There are a variety of glaucomas, most of which are asymptomatic until the late stages. The most common form of glaucoma is primary open angle glaucoma (POAG). Early detection is the key to limiting damage from this insidious painless cause of vision loss. While there are a number of risk factors for vision loss from glaucoma, the primary one is elevated intraocular pressure (IOP). Whether elevated IOP is the direct cause of damage or an inciting factor for neurotoxicity, ischemic damage, or other events, progressive changes occur without intervention. Elevated IOP occurs when aqueous humor (clear fluid inside the eye) that is necessary for intraocular nutrition, fails to drain properly. When this situation is sustained, damage to the optic nerve occurs. In some individuals, what is generally thought to be normal pressure (IOP) can result in damage to the optic nerve. This situation may be related to abnormal blood flow or other factors (see: Normal-tension glaucoma below). Primary open-angle glaucoma is generally a disorder seen in patents over the age of 40 years. Some instances of glaucoma secondary to developmental disorders may manifest themselves in infants, children or even young adults. There are other, less common, forms of glaucoma. Additionally, there are groups of patients classified as Ocular hypertensive and Glaucoma suspect.

Ocular Hypertension - Individuals with elevated IOP who have no signs of disease. The appearance of the optic nerve (structure) as well as visual fields (function) is considered healthy and normal.

Glaucoma Suspects - Individuals classified a glaucoma suspects have risk factors for developing glaucoma but show no clinical signs (healthy appearing optic nerves) or deficit in function (subjectively normal visual fields). The IOP is also in the normal range.

Open-angle Glaucoma - In this most common form of the disorder, the drainage pathway for aqueous leaving the eye is open. This determination is made with a contact lens placed on the eye, called a gonioscope. Open angle may be classified as primary (no obvious damage or reason for obstructed drainage) or secondary. In the secondary open-angle glaucomas, there is elevated IOP caused by pigmentary disorders in the eye, deposition of material on the drainage meshwork (exfoliation), damage from trauma to the eye, or abnormal drainage secondary to chronic topical steroid use.

Closed-angle Glaucoma - Closed angle glaucoma is the result of anatomical forces that physically block the drainage angle. Factors that predispose patients to this form of glaucoma are significant far-sightedness (hyperopia), small eyes, and older age. In particular, Asians tend to be predisposed to this form of glaucoma. Closure of the angle may be insidious but is often acute. The resulting spike of IOP causes painful, red eyes that represent an emergency to be managed expediently.

Normal Tension Glaucoma - Normal-tension glaucoma occurs in patients with IOP in the statistically normal range and is managed in a similar manner as other open angle forms of glaucoma.

Congenital Glaucoma - Congenital glaucoma occurs when a child is born with defects in the drainage system of the eye that slow the fluid drainage out of the eye.