Tissue in a healthy eye produces a transparent fluid called aqueous humor that travels through the eye before exiting through tiny channels on the surface of the eye. The balancing act between the production and outflow of this fluid determines the pressure inside your eye – your intraocular pressure. Glaucoma occurs when the intraocular pressure increases because the drainage of aqueous humor is hindered.
With primary open-angle glaucoma (POAG), the fluid blockage occurs in the tiny drainage channels in the eye, creating gradually higher pressures (intraocular pressures, or IOP) that permanently reduce a patient’s peripheral vision. POAG often has no symptoms and is generally treated through medication. While POAG has no blatant symptoms, if left unchecked it can cause the gradual and permanent loss of peripheral vision. Open angle glaucoma affects approximately 2.2 million Americans over age 40; another two million may have the disease and not know it.
Primary angle-closure glaucoma (PACG) is a less common but more aggressive form of glaucoma. Due to structural abnormalities in some patients’ eyes, over time the iris may come into contact with the cornea and block the flow of aqueous humor. Once the blockage occurs, the impact and symptoms are immediate, causing eye pain and redness, blurred vision, halos, headaches, and sometimes nausea and vomiting. Untreated PACG can cause rapid and permanent vision loss, so emergency care is crucial.
Even people with “normal” eye pressure can experience vision loss from glaucoma. This condition is called ‘normal tension’ glaucoma. In this type of glaucoma, the optic nerve is damaged even though the eye pressure is considered normal. Normal tension glaucoma is not well understood, but we do know that lowering eye pressure has been shown to slow progression of this form of glaucoma.
Childhood glaucoma is rare, and starts in infancy, childhood or adolescence. Like primary open-angle glaucoma, there are few, if any, symptoms in the early stage. Blindness can result if it is left untreated. Like most types of glaucoma, this type of glaucoma may run in families.
Your ophthalmologist or optometrist may tell you that you are at risk for glaucoma if you have one or more risk factors, including elevated eye pressures, a family history of glaucoma, a particular ethnic background, advanced age, or certain optic nerve conditions.
The animation below provides an introduction to Glaucoma.
The following topics are covered in this section on glaucoma:
The animation below provides an introduction to glaucoma.