Glaucoma
What is Glaucoma?
Glaucoma is a disease caused by increased intraocular pressure, or pressure inside the eye, resulting from a malfunction of the eye’s drainage system. If left untreated, elevated eye pressure can cause irreversible damage to the optic nerve and retinal fibres, resulting in progressive, permanent loss of vision. However, early detection and treatment can slow, or even halt, the progression of the disease.
What causes glaucoma?
The eye constantly produces aqueous, the clear fluid that fills the anterior chamber, which is the space between the cornea and iris. The delicate balance between the production and drainage of aqueous determines the eye’s intraocular pressure. Most people’s eye pressure will fall between 8 and 21 mmHg when measured. A pressure above 21 mmHg may indicate the possibility of developing glaucoma.
Common types of glaucoma
Open-angle glaucoma
Open-angle glaucoma, also called chronic open-angle or primary open-angle glaucoma, is the most common type of glaucoma. Left untreated, this may result in permanent damage to the optic nerve and retina. Eye drops are generally prescribed to lower eye pressure. In some cases, surgery is performed if the eye pressure cannot be adequately controlled with medical therapy.
Acute angle-closure glaucoma
Only about 10% of the population with glaucoma has this type. Acute angle-closure glaucoma occurs because of an abnormality of the structures in the front of the eye. In most of these cases, the space between the iris and cornea is too narrow for the aqueous to pass through adequately. In the worst-case scenario, the flow of aqueous becomes completely blocked and the IOP rises sharply, causing a sudden angle-closure attack.
While patients with open-angle glaucoma don’t typically have symptoms, those with angle-closure glaucoma may experience severe eye pain accompanied by nausea, blurred vision, rainbows around lights and a red eye. This problem is an emergency and should be treated by an ophthalmologist immediately. If left untreated, severe and permanent loss of vision can occur within a matter of days.
Signs and Symptoms
Glaucoma is an insidious disease because it rarely causes symptoms. Detection and prevention are only possible with routine eye examinations. However, certain types, such as angle-closure and congenital glaucoma, do cause symptoms. Angle-closure glaucoma is an emergency, and symptoms may include:
- Sudden decrease in vision
- Extreme eye pain
- Headache
- Nausea and vomiting
- Glare and light sensitivity
Detection and Diagnosis
Because glaucoma does not cause symptoms in most cases, those who are 40 or older should have an eye examination, including a measurement of intraocular pressure, about every two years. Those who are glaucoma suspects may need additional testing.
The glaucoma evaluation has several components. In addition to measuring intraocular pressure, your optometrist or eye doctor will also evaluate the health of the optic nerve at the back of your eye. They will test your peripheral vision and examine the structures in the front of the eye with a special lens before making a diagnosis.
Glaucoma Follow-up
The progression of glaucoma is monitored by your optometrist by giving you a visual field test. This test maps your peripheral vision, allowing the optometrist or doctor to determine the extent of vision loss from glaucoma and measure the effectiveness of the treatment. These visual field tests are carried out periodically to verify that eye pressure is being adequately controlled. A typical field test takes about 5 minutes per eye.
Treatment for Glaucoma
Most patients with glaucoma require only medication, usually eye drops, to control their eye pressure. Sometimes several medications are combined to achieve the best reduction in pressure.
Surgery is indicated when medical treatment does not lower the pressure satisfactorily. There are a few types of procedures, some involving laser, that can be performed under local anaesthetic.
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