Glaucoma is the second-leading cause of blindness in the world, according to the World Health Organization. And like many of the most insidious diseases known today, it often goes unnoticed until it’s too late.
“Most of the time, it’s an asymptomatic disease, and only late in the disease process does central vision become affected and evident to the patient. You can lose a lot of (peripheral) vision before you even notice it,” says Dr. Michael Donahoe, an ophthalmologist with Ophthalmology Consultants Ltd.
Considered a disease of the optic nerve, the most common type of glaucoma affects about 3 million Americans. “Open angle glaucoma is caused by fluid building up inside the eye, even though the drainage area appears to be significantly wide. This is the most common type,” explains Dr. Karen Rosen of Rosen Optometry. “Closed or narrow angle glaucoma is caused because the drainage area is narrow or closed, causing the fluid pressure to rise, sometimes to a very high level.”
Although glaucoma falls into these major categories, Donahoe points out that some people who have high pressure in the eye never develop glaucoma. Likewise, some individuals may develop the telltale optic nerve damage although their eye pressure falls within a normal range. Heredity plays a role—people who have a parent or sibling with glaucoma are two to four times more likely to develop it themselves.
“During the eye examination, higher intraocular pressure (IOP) can be detected, alerting that the patient is at risk for developing glaucoma,” says Dr. Mujtaba Qazi, director of clinical studies at Pepose Vision Institute. “The IOP is measured similar to detecting the air pressure in a tire, by pushing on the wall of the eye and measuring how much resistance there is.”
Ophthalmologists also examine the optic nerve using specialized instruments that allow them to detect ‘cupping,’ which indicates potential nerve damage. If high intraocular pressure or nerve-cupping is present, patients will be examined with additional tests to determine if there is any loss of peripheral vision, the earliest symptom of vision loss.
The good news is that, when detected early, glaucoma is very treatable. Prescription eye drops can lower pressure and help prevent further nerve damage. For patients who do not respond well to drops, laser procedures can allow eye fluid to drain more easily, also decreasing eye pressure.
Donahoe is involved in clinical trials for new treatments, including an implantable device that would deliver pressure-lowering medication, similar to insulin pumps that deliver sustained medication to diabetic patients. Another new therapy involves placing tiny shunts in the eye during cataract surgery to help drain fluid.
“It is important to have periodic eye examinations from an optometrist or an ophthalmologist in order to diagnose or rule out glaucoma,” Rosen says. “And if treatment for glaucoma is required, it’s important to continue with treatment unless an eye doctor says that it can be discontinued.”