Glaucoma refers to a group of eye conditions that lead to damage to the optic nerve, the nerve that carries visual information from the eye to the brain.
In many cases, damage to the optic nerve is due to increased pressure in the eye, also known as intraocular pressure (IOP).
Causes, incidence, and risk factors
Glaucoma is the second most common cause of blindness in the United States. There are four major types of glaucoma:
- Open-angle (chronic) glaucoma
- Angle-closure (acute) glaucoma
- Congenital glaucoma
- Secondary glaucoma
The front chamber of the eye is filled with a clear fluid called aqueous humor. There is a flow of aqueous through the eye, it is constantly being produced and it exits the eye through channels in an area called the anterior chamber angle, or simply the angle.
Anything that slows or blocks the flow of this fluid out of the eye will cause pressure to build up in the eye. This pressure is called intraocular pressure (IOP). In most cases of glaucoma, this pressure is high and causes damage to the major nerve in the eye, called the optic nerve.
Open-angle (chronic) glaucoma is the most common type of glaucoma.
- The cause is unknown. An increase in eye pressure occurs slowly over time. The pressure pushes on the optic nerve and the retina at the back of the eye
- Open-angle glaucoma tends to run in families. Your risk is higher if you have a parent or grandparent with open-angle glaucoma. People of African descent are at particularly high risk for this disease
Angle-closure (acute) glaucoma occurs when the exit of the aqueous humor fluid is suddenly blocked. This causes a quick, severe, and painful rise in the pressure within the eye (intraocular pressure).
- Angle-closure glaucoma is an emergency. This is very different from open-angle glaucoma, which painlessly and slowly damages vision
- If you have had acute glaucoma in one eye, you are at risk for an attack in the second eye, and your doctor is likely to recommend preventive treatment
- Dilating eye drops and certain medications may trigger an acute glaucoma attack
Congenital glaucoma often runs in families (is hereditary).
- It is present at birth
- It results from the abnormal development of the fluid outflow channels in the eye
Secondary glaucoma is caused by:
- Drugs such as corticosteroids
- Eye diseases such as uveitis
- Systemic diseases
- Most people have NO symptoms until they begin to lose vision
- Gradual loss of peripheral (side) vision (also called tunnel vision)
- Symptoms may come and go at first, or steadily become worse
- Sudden, severe pain in one eye
- Decreased or cloudy vision
- Nausea and vomiting
- Rainbow-like halos around lights
- Red eye
- Eye feels swollen
- Symptoms are usually noticed when the child is a few months old
- Cloudiness of the front of the eye
- Enlargement of one eye or both eyes
- Red eye
- Sensitivity to light
Signs and tests
An eye exam may be used to diagnose glaucoma. The doctor will need to examine the inside of the eye by looking through the pupil, often while the pupil is dilated. The doctor will usually perform a complete eye exam.
Checking the intraocular pressure alone (tonometry) is not enough to diagnose glaucoma because eye pressure changes. Pressure in the eye is normal in about 25% of people with glaucoma. This is called normal-tension glaucoma. There are other problems that cause optic nerve damage.
Tests to diagnose glaucoma include:
- Gonioscopy (use of a special lens to see the outflow channels of the angle)
- Tonometry test to measure eye pressure
- Optic nerve imaging (photographs of the inside of the eye)
- Pupillary reflex response
- Retinal examination
- Slit lamp examination
- Visual acuity
- Visual field measurement
The goal of treatment is to reduce eye pressure. Depending on the type of glaucoma, this is done using medications or surgery.
Open-angle glaucoma treatment:
Most people with open-angle glaucoma can be treated successfully with eye drops. Most eye drops used today have fewer side effects than those used in the past. You may need more than one type of drop. Some patients may also be treated with pills to lower pressure in the eye. Newer drops and pills are being developed that may protect the optic nerve from glaucoma damage.
Some patients will need other forms of treatment, such as a laser treatment, to help open the fluid outflow channels. This procedure is usually painless. Others may need traditional surgery to open a new outflow channel.
Angle-closure glaucoma treatment:
Acute angle-closure attack is a medical emergency. Blindness will occur in a few days if it is not treated. Drops, pills, and medicine given through a vein (by IV) are used to lower pressure. Some people also need an emergency operation, called an iridotomy. This procedure uses a laser to open a new channel in the iris. The new channel relieves pressure and prevents another attack.
Congenital glaucoma treatment:
This form of glaucoma is almost always treated with surgery to open the outflow channels of the angle. This is done while the patient is asleep and feels no pain (with anesthesia).
With good care, most patients with open-angle glaucoma can manage their condition and will not lose vision, but the condition cannot be cured. It’s important to carefully follow up with your doctor.
Rapid diagnosis and treatment of an attack is key to saving your vision. Seek emergency care immediately if you have symptoms of an angle-closure attack.
Early diagnosis and treatment is important. If surgery is done early enough, many patients will have no future problems.
There is no way to prevent open-angle glaucoma, but you can prevent vision loss from the condition. Early diagnosis and careful management are the keys to preventing vision loss.
Most people with open-angle glaucoma have no symptoms. Everyone over age 50 should have a dilated eye examination once a year, and more often if in a high-risk group. Those in high-risk groups include people with a family history of open-angle glaucoma and people of African heritage.
People at high risk for acute glaucoma may opt to undergo laser iridotomy before having an attack. Patients who have had an acute episode in the past may have the procedure to prevent a recurrence.