Glaucoma refers to a group of disorders that lead to damage to the optic nerve, the nerve that carries visual information from the eye to the brain.
Open-angle glaucoma; Chronic glaucoma; Closed-angle glaucoma; Congenital glaucoma
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:
- Angle-closure (acute) glaucoma
- Congenital glaucoma
- Open-angle (chronic) glaucoma
- Secondary glaucoma
All four types of glaucoma are characterized by increased pressure within the eyeball, and therefore all can cause progressive damage to the optic nerve. Open-angle (chronic) glaucoma is by far the most common type of glaucoma.
The front part of the eye is filled with a clear fluid called the aqueous humor. This fluid is constantly made in the back of the eye. It leaves the eye through channels in the front (anterior) chamber of the eye, and eventually drains into the bloodstream. The channels that drain the aqueous humor are in an area called the anterior chamber angle, or simply the angle.
Angle-closure (acute) glaucoma is caused by a shift in the position of the iris of the eye that suddenly blocks the exit of the aqueous humor fluid. 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 systemic medications may trigger an acute glaucoma attack if you are at risk.
Congenital glaucoma often runs in families (hereditary). It is present at birth, and is the result of the abnormal development of the fluid outflow channels in the eye.
In open-angle glaucoma, the cause is essentially unknown. An increase in eye pressure pushes on the junction of the optic nerve and the retina at the back of the eye, reducing the blood supply to the optic nerve.
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.
Secondary glaucoma is caused by:
- Drugs such as corticosteroids
- Eye diseases such as uveitis
- Systemic diseases
- Gradual loss of peripheral (side) vision
- Most people have no symptoms until they lose vision
- Decreased or cloudy vision
- Nausea and vomiting
- Pupil does not react to light
- Red eye
- Severe eye pain, facial pain
- Swelling of the eye
Cloudiness of the front of the eye
Enlargement of one eye or both eyes
Sensitivity to light
Signs and tests
An examination of the eye may be used to diagnose glaucoma. However, checking the intraocular pressure alone (tonometry) is not enough because eye pressure changes. The doctor will need to examine the inside of the eye by looking through the pupil, often while the pupil is dilated.
Usually the doctor will perform a complete examination of the eyes.
Tests may include:
- Gonioscopy (use of a special lens to see the outflow channels of the angle)
- Intraocular pressure measurement by tonometry
- Optic nerve imaging (photographs of the interior of the eye)
- Pupilary reflex response
- Retinal examination
- Slit lamp examination
- Visual acuity
- Visual field measurement
There are a number of treatments each specific to the various type of glaucoma that one has.