Glaucoma is a group of diseases that can damage the eye’s optic nerve and result in vision loss and in some cases blindness. Glaucoma occurs when the normal fluid pressure inside the eyes slowly rises. However, with early treatment, in most cases, a regular eye examination can protect your eyes against serious vision loss.
The Optic Nerve
The optic nerve is a bundle of more than 1 million nerve fibers. It connects the retina to the brain. The retina is the light-sensitive tissue at the back of the eye. You need a healthy optic nerve for good vision.
Forms of Glaucoma
Open-angle glaucoma is the most common form of glaucoma. Some people have other types of the disease.
Low-tension or normal-tension glaucoma
Optic nerve damage and narrowed side vision occur in people with normal eye pressure. Lowering eye pressure at least 30 percent through medicines slows the disease in some people. Glaucoma may worsen in others despite low pressures. Comprehensive medical history is important in identifying other potential risk factors, such as low blood pressure, that contribute to low-tension glaucoma. If no risk factors are identified, the treatment options for low-tension glaucoma are the same as for open-angle glaucoma.
The fluid at the front of the eye cannot reach the angle and leave the eye. The angle gets blocked by part of the iris. People with this type of glaucoma have a sudden increase in eye pressure. Symptoms include severe pain and nausea, as well as redness of the eye and blurred vision. If you have these symptoms, you need to seek treatment immediately.
Children are born with a defect in the angle of the eye that slows the normal drainage of fluid. These children usually have obvious symptoms, such as cloudy eyes, sensitivity to light, and excessive tearing. This can usually be treated through surgery.
These can develop as complications of other medical conditions. These types of glaucomas are sometimes associated with eye surgery or advanced cataracts, eye injuries, certain eye tumors, or uveitis (eye inflammation). Pigmentary glaucoma occurs when pigment from the iris flakes off and blocks the meshwork, slowing fluid drainage. Treatment includes medicines, laser surgery, or conventional surgery.
How does open-angle glaucoma damage the optic nerve?
In the front of the eye is a space called the anterior chamber. A clear fluid flows continuously in and out of the chamber and nourishes nearby tissues. The fluid leaves the chamber at the open angle where the cornea and iris meet. When the fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye. Sometimes, when the fluid reaches the angle, it passes too slowly through the meshwork drain. As the fluid builds up, the pressure inside the eye rises to a level that may damage the optic nerve. When the optic nerve is damaged from increased pressure, open-angle glaucoma–and vision loss–may result. That’s why controlling pressure inside the eye is important.
Eye Pressure and Glaucoma
Increased eye pressure means you are at risk for glaucoma, but does not mean you have the disease. A person has glaucoma only if the optic nerve is damaged. If you have increased eye pressure but no damage to the optic nerve, you do not have glaucoma.
Whether you develop glaucoma depends on the level of pressure your optic nerve can tolerate without being damaged. This level is different for each person. That’s why a comprehensive dilated eye examination is very important. It can help your optometrist determine what level of eye pressure is normal for you.
Also, glaucoma can develop without increased eye pressure. This form of glaucoma is called low-tension or normal-tension glaucoma. It is not as common as open-angle glaucoma.
Who is at risk?
There are several risk factors which make the onset of glaucoma more likely.
Age – primary open angle glaucoma becomes much more common with increasing age. It is uncommon below the age of 40, but the number of people with the condition rises from about two per cent of people over the age of 40 to more than five per cent for those over the age of 80.
Blood pressure – people with low blood pressure, in relation to the eye pressure, are at greater risk.
Ethnicity – people of African-Caribbean origin are at four times greater risk of developing primary open angle glaucoma, when compared with those of a European origin. The condition also tends to come on at an earlier age and be more severe. People of Asian origin are at an increased risk of developing primary angle closure glaucoma.
Family history – there is an increased risk of developing glaucoma if you have a close blood relative with the condition. If you have glaucoma, don’t forget to tell your relatives about the condition and the need for them to be tested.
Short sight – people with short sight (myopia) are at increased risk of developing glaucoma, and should ensure that they are regularly tested.
Long sight – Long sighted people are known to be at increased risk of developing angle closure.
Diabetes – people with diabetes may be at increased risk of developing glaucoma, although it is not known whether there is a direct link between the two conditions. However, all people with diabetes should have regular routine eye examinations for diabetic eye diseases.
Symptoms and Detection
At first, there are no symptoms, your vision stays normal, and there is no pain. However, as the disease progresses, a person with glaucoma may notice his or her side vision gradually failing. That is, objects in front may still be seen clearly, but objects to the side may be missed.As glaucoma remains untreated, people may miss objects to the side and out of the corner of their eye. Without treatment, people with glaucoma will slowly lose their peripheral (side) vision. They seem to be looking through a tunnel. Over time, the straight-ahead vision may decrease until no vision remains. Glaucoma can develop in one or both eyes.
Glaucoma is detected through a comprehensive eye exam that includes:
Visual acuity test – this eye chart test measures how well you see at various distances. A tonometer measures pressure inside the eye to detect glaucoma.
Visual field test – this test measures your side (peripheral) vision. It helps your eye care professional tell if you have lost side vision, a sign of glaucoma.
Dilated eye exam – drops are placed in your eyes to widen, or dilate, the pupils. Your eye care professional uses a special magnifying lens to examine your retina and optic nerve for signs of damage and other eye problems. After the exam, your close-up vision may remain blurred for several hours.
Tonometry – an instrument measures the pressure inside the eye.
Protecting you vision
Studies have shown that the early detection and treatment of glaucoma, before it causes major vision loss, is the best way to control the disease. So, if you fall into one of the high-risk groups for the disease, make sure to have your eyes examined regularly by one of our optometrists.
If you are being treated for glaucoma, be sure to take your glaucoma medicine every day and visit your optometrist regularly. You can book an appointment with one of our qualified optometrists by clicking here.