Types of Glaucoma
Glaucoma is group of diseases which result in damage to the nerves that connect the eye to the visual centers of the brain (optic nerve). The type of glaucoma influences how quickly damage occurs, which symptoms may be associated and what treatment options are available. The two main types of glaucoma are open angle and closed angle glaucoma. The “angle” refers to the angle formed between the iris and cornea inside the eye. The space between these two structures is important as the drainage system of the eye (trabecular meshwork) is located where the iris and cornea meet.
Open Angle Glaucoma
Open angle glaucoma is a collection of diseases affecting about 3 million Americans. The most common form is Primary Open Angle Glaucoma. The disease is chronic and the majority of cases respond well to medication, especially if detected early. Early detection and appropriate follow up are vital since the majority of patients with early to moderate glaucoma do not have symptoms from the disease.
Other forms of Open Angle Glaucoma
Low Tension/Normal Tension – Individuals with this form of glaucoma do not have an elevated intraocular pressure yet still have damage occurring in their eye. Treatment is similar to other forms of open angle glaucoma where medication and laser surgery is offered as first line therapy but many patients require surgery to achieve the low intraocular pressure needed to minimize future damage.
Pigmentary Glaucoma- In pigmentary glaucoma, the iris rubs against the cables (zonules) that support the lens behind the iris. The contact between these two structures causes pigment to be released inside the eye. The pigment then clogs the drainage system of the eye (trabecular meshwork). Patients are often younger (20-40 years old) and near sighted. Patients with this form of glaucoma may have visual symptoms (halos, blurred vision) after exercising. Medications and laser surgery (laser trabeculoplasty) work well for this condition but sometimes surgery is required. Patients with pigmentary dispersion syndrome have similar findings (iris-zonule contact, pigment released inside the eye) but without elevated pressure or signs of damage to their nerves.
Closed Angle Glaucoma
Angle closure glaucoma can develop quickly (acute angle closure) or slowly (chronic angle closure glaucoma). Angle closure can result in sudden, dramatic symptoms including blurred vision, severe headache, nausea and vomiting. Initial therapy is directed at improving the position of the iris in relation to the cornea. This may be achieved by laser peripheral iridotomy, reshaping the iris using a laser (laser iridoplasty) or in some cases removal of a cataract to increase the space inside the eye. Patients may require medication or further glaucoma surgeries depending on the degree of damage to the nerves and drainage system.
Other Forms of Glaucoma:
Individuals with a history of uveitis (inflammation in the eye) are at risk of developing glaucoma damage. This can be from inflammatory debris clogging the trabecular meshwork, inflammation causing the iris to adhear to the cornea causing blockage of the trabecular meshwork, or due to prolonged steroid use which can result in elevated intraocular pressure. These conditions are often manageable with topical medications. However some cases patients may require surgery. Any surgical interventions are coordinated closely with the doctor managing the uveitis.
In neovascular glaucoma, abnormal blood vessels grow across the trabecular meshwork (neovascularization of the angle) causing the drainage system to be clogged and pressure inside the eye to elevate. The sudden elevation in pressure can result in blurred vision, eye pain, headaches and halos. The abnormal blood vessels most commonly form in individuals with advanced diabetic damage in the eye but can also form if there was a prior occlusion of the vessels in the eye such as a central retinal vein occlusion, branch retinal vein occlusion or retinal artery occlusion. Treatment is initially directed at causing regression of the abnormal blood vessels. This may require laser surgery or injections of medications into the eye. Patients may ultimately require surgery if pressures remain elevated despite medication to lower pressure in the eye.
Patients with risk factors for developing glaucoma are referred to as glaucoma suspects. The risk factors may include a family history, elevated intraocular pressure, narrow angles, abnormal shaped optic nerves or systemic conditions such as diabetes. Your doctor can tell you if you are low risk or high risk. The level of risk will dictate how frequently you are seen and whether or not treatment is started to minimize the risk of developing glaucoma.