Glaucoma is an eye disease causing damage to the optic nerve. The optic nerve is the part of the eye that carries visual signals from the retina to the brain. The brain then interprets these signals into images that you see. In the healthy eye, a clear fluid called aqueous humor circulates inside the front portion of your eye. 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, over time, causes damage to the optic nerve fibers.
Glaucoma can lead to blindness if left untreated. Only about half of all people that have glaucoma are even aware that they have the disease. Patients with glaucoma do not have any symptoms until late in the disease, causing slow silent visual loss without any knowledge. Once vision loss occurs, it cannot be reversed. Fortunately, early detection and treatment can help preserve your vision.
Types of glaucoma:
The most common form of glaucoma is called primary open-angle glaucoma. It occurs when the drainage system of the eye called the trabecular meshwork gradually becomes less efficient at draining fluid. As this happens, your eye pressure, called intraocular pressure (IOP), rises. Raised eye pressure leads to damage of the optic nerve. Damage to the optic nerve can occur at different eye pressures among different patients. Your ophthalmologist 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.
Although normal eye pressure is considered a measurement less than 21 mm Hg, this can be misleading. Some people have a type of glaucoma called normal-tension, or low-tension glaucoma. Their eye pressure is consistently below 21mm Hg, but optic nerve damage and visual field loss still occur. People with normal-tension glaucoma typically receive the same methods of treatment used for open-angle glaucoma.
A less common form of glaucoma is closed angle (or narrow-angle glaucoma or angle-closure glaucoma). Closed-angle glaucoma occurs when the drainage angle of the eye becomes blocked. Unlike open-angle glaucoma, eye pressure usually goes up very fast. The pressure rises because the iris — the colored part of the eye — partially or completely blocks off the drainage angle. People of Asian descent and those with hyperopia (farsightedness) tend to be more at risk for developing this form of glaucoma. If the drainage angle becomes completely blocked, eye pressure rises quickly resulting in a closed-angle glaucoma attack.
Symptoms of an attack include:
Severe eye or brow pain
Redness of the eye
Decreased or blurred vision
Seeing colored rainbows or halos
A closed-angle glaucoma attack is a medical emergency and must be treated immediately. Unfortunately, people at risk for developing closed-angle glaucoma often have few or no symptoms before the attack.People at risk for closed-angle glaucoma should avoid over-the-counter decongestants and other medications where the packaging states not to use these products if you have glaucoma
Secondary glaucoma is glaucoma that results from another eye condition or disease. For example, someone who has had an eye injury, someone who is on long-term steroid therapy or someone who has a tumor may develop secondary glaucoma.
Ocular hypertension is a condition where someone has higher eye pressure than normal, but does not have other signs of glaucoma, such as optic nerve damage or blank spots that show up in their peripheral (side) vision when tested. Individuals with ocular hypertension are at higher risk for developing glaucoma later relative to those with lower, or average eye pressure. Just like people with glaucoma, people with ocular hypertension need to be closely monitored by an ophthalmologist to ensure they receive appropriate treatment.