Types of Glaucoma
Glaucoma is broadly categorized as open angle or closed angle. Within these categories, there are many subtypes of glaucoma. Since childhood glaucoma behaves differently, it is discussed separately. Click any topic for more details.
Open Angle Glaucoma
This is the most common type of glaucoma diagnosed in the United States. It is associated with high pressure and is thought to be due to poor drainage through the trabecular meshwork. There are typically no early symptoms and it is often diagnosed on routine examination.
Normal Tension Glaucoma
In this disease, typical glaucomatous nerve changes occur in the absence of high pressure (>21 mm Hg). It is more common is those of Japanese ancestry and may be associated with migraines and low blood pressure. A large study called the Collaborative Normal Tension Glaucoma Study looked at 145 eyes with this disease. About half of the eyes were treated (with a goal of a 30% reduction in highest measured pressure) and half were simply followed. At 5 years, 80% of the treated eyes were stable while only 40% of untreated eyes remained unchanged. This study showed that lowering the pressure, even if it was never high, can slow or stop the worsening of glaucoma.
Pigment Dispersion Syndrome/Pigmentary Glaucoma
This is a disease typically seen in young, near-sighted people.Men are more affected than women and usually affected in the third decade of life. While there are few symptoms, some patients may experience blurry vision or haloes after jarring exercise (like basketball or racquetball). One eye may be more affected than the other. In this disease, pigment is released from the back of the iris and deposits on the cornea and in the trabecular meshwork. This pigment essentially "clogs the drain" and can lead to high pressures. Not everyone with evidence of pigment dispersion develops glaucoma. However, those that do may develop very high pressures that need to be aggressively treated to prevent vision loss.
This is a disease that was once thought to be associated with Scandinavian ancestry. While this disease is commonly found in Iceland and Sweden, it is found all over the world. In pseudoexfoliation syndrome, a white material is made by the eye and deposits on the lens, iris and trabecular meshwork. This material "clogs the drain" and can lead to very high pressures. In addition, it weakens the support of the lens and can make removing a cataract more difficult. The appearance can be quite asymmetric, with one eye affected much more than the other. Close monitoring and aggressive treatment are important to preventing vision loss.
In a group of people, treatment with steroids can cause elevated eye pressure. While it is most common with topical steroid drops or steroid injections around the eye, it has been reported with oral steroids and less commonly, inhaled steroids (nasal sprays and asthma inhalers). Studies have shown that about 1/3 of people treated with steroid drops will have a moderate rise in eye pressure. However, in 5% of people the pressure will rise >30 mm Hg. The people at highest risk are those with glaucoma or a family history of glaucoma. Most of the time, the pressure will normalize if the steroid can be stopped or switched to a weaker formula. However, in a small group of people, the pressure remains chronically elevated.
Patients with inflammation can develop glaucoma. During a flare, inflammatory cells in the eye can block the trabecular meshwork and cause a transient rise in pressure that may subside when the inflammation resolves. Chronic inflammation or repeated attacks can also permanently damage the trabecular meshwork. In these cases, eye pressure remains elevated even after the inflammation resolves.
Acute Angle Closure Glaucoma
Unlike open angle glaucoma, acute angle closure is accompanied by symptoms including eye pain, headache, blurry vision, tearing and even nausea. People who are far-sighted are at higher risk, as well as women and those of East Asian heritage.
In this disease, fluid cannot get around the lens to the front part of the eye. As a result, pressure builds behind the iris, bowing the iris forward and closing the drain. If this happens, the eye pressure will rise very quickly, reaching the 60s or 70s in a matter of hours. This is an ophthalmologic emergency, requiring urgent treatment to lower the pressure and prevent permanent vision loss.
Chronic Angle Closure Glaucoma
Unlike acute angle closure glaucoma, in this disease the drain closes slowly causing a gradual rise in eye pressure. This commonly occurs in people who have narrow angles, where the iris is in close contact with the trabecular meshwork. Over time, the iris will scar to the meshwork causing angle closure. Chronic angle closure can lead to high eye pressures without pain and can be difficult to control with medications alone.
In this disease, new blood vessels grow over the trabecular meshwork. This problem occurs most commonly in diabetics, patients with a central retinal vein occlusion or ocular ischemic syndrome. In these diseases, the eye senses a poor blood flow and releases a chemical signal to stimulate new blood vessel growth. Unfortunately, the new blood vessels are fragile and if they grow unchecked, they will lead to scarring and closure of the drain. Once the drain has scarred, this type of glaucoma is very difficult to control medically.
While chronic inflammation can damage the drain of the eye leading to open angle glaucoma, it can also leading to scarring and closure of the drain. If the angle has scarred closed, the pressure is less likely to be controlled medically.
In this disease, glaucoma develops shortly after birth. The hallmarks of congenital glaucoma are enlarging eyes, tearing and light sensitivity. Diagnosis often requires an exam under anesthesia in the operating room. Medications have many side effects in infants and so this is primary a surgically treated disease which requires prompt intervention to prevent long term sequelae. Follow up will include serial exams under anesthesia to assess the pressure and rate of growth of the eye. Caring for infants with congenital glaucoma requires the assistance of a pediatric ophthalmologist who can assess the development of vision and the need for glasses or patching.