What is Glaucoma?
Glaucoma is a disease caused by increased intraocular pressure (pressure inside the eye) resulting from a malfunction of the eye’s drainage system. If left untreated, an elevated eye pressure causes irreversible damage the optic nerve and retinal fibers resulting in a 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 (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 when measured will fall between 8 and 21mmHg. A pressure above 21 mm Hg may indicate the possibility of you developing Glaucoma.
Common types of glaucoma
- Open Angle
Open angle (also called chronic open angle or primary open angle) is the most common type of glaucoma. Left untreated, this may result in permanent damage of the optic nerve and retina. Eye drops are generally prescribed to lower the eye pressure. In some cases, surgery is performed if the eye pressure cannot be adequately controlled with medical therapy.
- Acute Angle Closure
Only about 10% of the population with glaucoma has this type. Acute angle closure 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, 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 will occur in 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, do cause symptoms. Angle Closure (emergency) symptoms are as follows:-
- Sudden decrease of vision
- Extreme eye pain
- 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 the 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 the 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 the peripheral vision, and examine the structures in the front of the eye with a special lens before making a diagnosis.
The progression of glaucoma is monitored by your optometrist by giving you a visual field test. This test maps the peripheral vision, allowing the optometrist or doctor to determine the extent of vision loss from glaucoma and a measure of the effectiveness of the treatment. These Visual Field tests are carried out periodically to verify that the eye pressure is being adequately controlled. A typical Field Test takes about 5mins per eye.
Most patients with glaucoma require only medication (drops) to control their eye pressure. Sometimes several medications are combined to give the best reduction in pressure.
Surgery is indicated when medical treatment (drops) fails to lower the pressure satisfactorily. They are a few types of procedures, some involving laser that can be done in rooms under a local anaesthetic.