Glaucoma is known as the “silent thief of sight,” because in the most common form, there are typically no early symptoms as the disease sneaks up on its victims, robbing them of side vision first and then, over time, zeroing in until it’s like looking through a narrow tunnel. Finally, glaucoma takes away vision altogether.
Glaucoma is a major cause of vision loss in the U.S. Today, it affects about three million Americans; but according to the National Eye Institute, that number could more than double by 2050. And according to the World Health Organization, it’s the second leading cause of blindness in the world.
In the most common form of glaucoma, called primary open angle glaucoma, nerve damage results from increased pressure inside the eye. This pressure happens when the fluid that circulates in the eye drains too slowly. To maintain a constant healthy eye pressure, your eye continually produces a small amount of aqueous humor while an equal amount of this fluid flows out of your eye. If you have glaucoma, the aqueous humor does not flow out of the eye properly. Fluid pressure in the eye builds up and causes damage to the optic nerve fibers.
The optic nerve acts like a data cable with over a million wires and is responsible for carrying images from the eye to the brain. When the nerve cells or “wires” in the cable are damaged, the flow of visual information is disrupted. Unlike a TV, which might be fixed with a new cable, there is no way to reverse damage to the optic nerve.
Over time, raised intraocular pressure (IOP) causes damage to the nerve fibers. If the drainage angle becomes completely blocked, eye pressure rises quickly, resulting in a narrow-angle glaucoma attack, with severe eye and brow pain, nausea and vomiting. This kind of glaucoma attack is a medical emergency and must be treated immediately. This is unlike the open angle glaucoma which has no symptons until visual loss is experienced. People of Asian descent and those with hyperopia (farsightedness) tend to be more at risk for narrow-angle glaucoma (also known as angle-closure glaucoma or closed-angle glaucoma).
Damage to the optic nerve can occur at different eye pressures among different patients. Your eye doctor establishes a target eye pressure for you that he or she predicts will protect your optic nerve from further damage. Different patients have different target pressures. Some patients have an eye pressure that is consistently below 21 mm Hg, but optic nerve damage and visual field loss still occur. Adults with no symptoms of, or risk factors for, eye disease should have a complete eye disease screening by age 40 — the time when early signs of disease and changes in vision may start to happen. Populations tending to have a higher risk factor for developing glaucoma include those who: are age 40 and up; have a family history of glaucoma; are of African or Hispanic ancestry; have farsightedness or nearsightedness; have elevated eye pressure or past eye injury; have a thinner central cornea; do not have eye examinations when they are recommended; have low blood pressure; or have conditions that affect blood flow, such as migraines, diabetes and low blood pressure.
Based on the results of the initial screening, your eye care provider will let you know how often to return for follow-up exams. Adults 65 or older should have an eye exam every year or as recommended by your provider. If you do not have an eye care provider, our Summit Eye Care staff welcomes you to make an appointment for an examination.