Open-angle glaucoma is the most common form of the disease, accounting for about 90 percent of all glaucoma cases, according to the Glaucoma Research Foundation. Here is a breakdown of the different types of open-angle glaucoma:
Primary open-angle glaucoma (POAG) occurs when the eye’s drainage meshwork becomes clogged over time. As a result, fluid builds up and pressure inside the eye rises to a level that damages the optic nerve. POAG usually has no symptoms or warning signs. It develops slowly and visual loss may not be noticeable for years.
Secondary open-angle glaucoma develops as the result of other medical or ophthalmic conditions and can occur in one or both eyes. These secondary conditions may include high blood pressure, poorly controlled diabetes, traumatic eye injury, certain drugs like steroids, an advanced case of cataracts, and uveitis.
Secondary forms of open-angle glaucoma include:
- Uveitic glaucoma—Because uveitis causes swelling of the middle layer of the eye (the uvea), it can raise intraocular pressure when those inflammatory cells clog the eye’s drainage canals and prevent fluid outflow. Elevated pressure may also result from the corticosteroids that ophthalmologists typically use to treat uveitis.
- Pseudoexfoliative glaucoma—This form of glaucoma is triggered by a flaky material that peels off the outer layer of the lens and accumulates in the meshwork of the eye. This buildup of protein in the drainage system impedes normal drainage of fluids and causes eye pressure to rise. Patients with this aggressive disorder may experience more episodes of high pressure and more fluctuations in pressure than people with other types of glaucoma.
- Pigmentary glaucoma – This form occurs when pigment granules from the back surface of the iris (the colored part of the eye) dislodge and clog the eye’s drainage canal, causing eye pressure to rise.
- Neovascular glaucoma—Most often associated with diabetes, this form of glaucoma is the result of new blood vessels forming on the iris and over the eye’s drainage channels (the trabecular meshwork). This abnormality blocks fluids from leaving the eye, which causes intraocular pressure to rise.
Normal-tension glaucoma (also known as low-tension glaucoma) occurs when the optic nerve is damaged despite the fact eye pressure is within the statistically normal range (12-22 mm Hg). Risk factors include a family history of the disease, a history of systemic heart disease like irregular heart rhythm, low blood pressure, and Japanese ancestry.
Juvenile open-angle glaucoma is a form of primary open-angle glaucoma with an onset between 10 and 30 years of age. This is a rare and genetically predisposed form of glaucoma for which moderate to extreme nearsightedness is often an underlying factor.