When patients are at the office for their eye exam, we measure the eye( or intraocular) pressure and the question frequently arises as to why we are doing this . The answer is that we are screening for glaucoma. Subsequently, this generates another question which is, “What exactly is glaucoma?”
Glaucoma is a disease of the optic nerve, the pathway connecting the eyeball and retina to the brain. Although the relationship is complex, patients with glaucoma generally have an elevated intraocular pressure. This high eye pressure, in turn, either by “pressing” on the microscopic fibers of the nerve or by reducing the blood flow to them, causes slow, but progressive damage. As suggested, the exact mechanism is complex, and there are even some patients who develop glaucoma despite relatively normal eye pressures.
Most glaucoma patients, approximately 90%, have what is known as open-angle glaucoma. Here, the fluid in the front of the eye, known as the aqueous humor, easily gets to the area in which it drains from the eye, but the “drain” (also known as the trabecular meshwork) is not as effective as it once was. The other 10% have what is known as narrow-angle glaucoma. In this case, the path to the drain is narrowed and the normal flow of aqueous humor is compromised. Whether open or narrow, both types of glaucoma typically result in elevated eye pressure and gradual loss of vision. In rare cases, the narrow type may be an acute event accompanied by severe pain and rapid loss of vision. Most glaucoma patients, however, have no symptoms until late in the course of the disease and have no idea of the subtle damage that is being done. This is why it is so important for patients to have their eye pressure checked and be screened for glaucoma!
How common is glaucoma? It is estimated that approximately 1-2% of the world’s population has some form of the disease. It is the second leading cause of blindness worldwide and the leading cause in African Americans. In addition to a screening of intraocular pressure, ophthalmologists and optometrists perform tests such as visual field testing, optic nerve fiber analysis and direct visualization of the nerve. These tests, all important pieces of the puzzle, give the doctor a sense of how the nerve appears(versus what is considered normal) as well as how the nerve is functioning. Thus, the eye doctor can confirm the diagnosis of glaucoma and initiate treatment. This will be the subject of my next blog.