Glaucoma is not just one eye disease, but a group of eye conditions resulting in optic nerve damage, which may cause loss of vision. Abnormally high pressure inside your eye (intraocular pressure) usually, but not always, causes this damage.
Glaucoma is one of the leading causes of blindness in the United States. Glaucoma can damage your vision so gradually you may not notice any loss of vision until the disease is at an advanced stage. The most common type of glaucoma, primary open-angle glaucoma, has no noticeable signs or symptoms except gradual vision loss.
Early diagnosis and treatment can minimize or prevent optic nerve damage and limit glaucoma-related vision loss. It’s important to get your eyes examined regularly, and make sure your eye doctor measures your intraocular pressure.
For reasons that doctors don’t fully understand, increased pressure within the eye (intraocular pressure) is usually, but not always, associated with the optic nerve damage that characterizes glaucoma. This pressure is due to a buildup of a fluid (aqueous humor) that flows in and out of your eye.
This fluid normally exits your eye through a drainage system at the angle where the iris and the cornea meet. When the drainage system doesn’t work properly, the fluid can’t filter out of the eye at its normal rate, and pressure builds within your eye.
Primary open-angle glaucoma
In primary open-angle glaucoma, the drainage angle formed by the cornea and the iris remains open, but the drainage channels (trabecular meshwork) in the angle are partially blocked, causing the fluid to drain out of the eye too slowly. This causes fluid to back up in your eye, and pressure gradually increases within your eye.
Damage to the optic nerve doesn’t cause symptoms or pain, and it happens so slowly that you may lose an extensive amount of vision before you’re even aware of a problem. The exact cause of primary open-angle glaucoma remains unknown.
Angle-closure glaucoma, also called closed-angle glaucoma, occurs when the iris bulges forward to narrow or block the drainage angle formed by the cornea and the iris. As a result, fluid can’t adequately flow through and exit your eye, and your eye pressure may increase abruptly. Angle-closure glaucoma usually occurs suddenly (acute angle-closure glaucoma), but it can also occur gradually (chronic angle-closure glaucoma).
Some people with an abnormally narrow drainage angle may be at risk of developing angle-closure glaucoma.
If you have a narrow drainage angle, sudden dilation of your pupils may trigger acute angle-closure glaucoma.
In normal-tension glaucoma, your optic nerve becomes damaged. However, your eye pressure remains within the normal range. Doctors don’t understand why this occurs. You may have a sensitive optic nerve, or you may have less blood being supplied to your optic nerve. This lack of blood supply could be caused by atherosclerosis — an accumulation of fatty deposits (plaques) in the arteries — or another condition limiting your blood circulation.
Some infants or children may be diagnosed with glaucoma. Rarely, some children may be born with glaucoma (congenital glaucoma), develop glaucoma in the first few years of life (infantile glaucoma) or develop glaucoma after age 4 or 5 (juvenile glaucoma). Children usually won’t have any symptoms. However, they have optic nerve damage, which may be caused by angle blockages or malformations (primary infantile glaucoma), or it could develop as the result of other conditions (secondary glaucoma).
In pigmentary glaucoma, pigment granules from your iris build up in the drainage channels (trabecular meshwork), slowing or blocking fluid exiting your eye. Physical activities, such as jogging, sometimes stir up the pigment granules, depositing them on the trabecular meshwork and causing intermittent pressure elevations.
The most common types of glaucoma — primary open-angle glaucoma and angle-closure glaucoma — have completely different symptoms.
Primary open-angle glaucoma signs and symptoms include:
- Gradual loss of peripheral vision, usually in both eyes
- Tunnel vision in the advanced stages
Acute angle-closure glaucoma signs and symptoms include:
- Eye pain
- Nausea and vomiting (accompanying the severe eye pain)
- Sudden onset of visual disturbance, often in low light
- Blurred vision
- Halos around lights
- Reddening of the eye
Both open-angle and angle-closure glaucoma can be primary or secondary conditions. They’re called primary when the cause is unknown and secondary when the condition can be traced to a known cause, such as eye injury, medications, certain eye conditions, inflammation, tumor, advanced cataract or diabetes. In secondary glaucoma, the signs and symptoms can include those of the primary condition as well as typical glaucoma symptoms.
When to see a doctor
Don’t wait for noticeable eye problems. Primary open-angle glaucoma gives few warning signs until permanent damage has already occurred. Regular eye exams are the key to detecting glaucoma early enough to successfully treat your condition and prevent further progression of your condition.
The American Academy of Ophthalmology recommends a comprehensive eye exam for all adults starting at age 40, and every three to five years after that if you don’t have any glaucoma risk factors. If you have other risk factors or you’re older than age 60, you should be screened every one to two years. If you’re African-American, your doctor likely will recommend periodic eye exams starting between ages 20 and 39.
In addition, be aware that a severe headache or pain in your eye, nausea, blurred vision, or halos around lights may be the symptoms of an acute angle-closure glaucoma attack. If you experience some or several of these symptoms together, seek immediate care at an emergency room or at an eye doctor’s (ophthalmologist’s) office right away.