Glaucoma is a condition which can affect sight, usually due to build -up of pressure within the eye. Glaucoma often affects both eyes, usually to varying degrees. One eye may develop glaucoma quicker than the other. The eyeball contains a fluid called aqueous humour which is constantly produced by the eye, with any excess drained though tubes.
Glaucoma develops when the fluid cannot drain properly and pressure builds up, known as the intraocular pressure. This can damage the optic nerve (which connects the eye to the brain) and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).
Chronic open-angle glaucoma affects up to two in every 100 people over 40 years old and around five in every 100 people over 80 years old. Some types of glaucoma, such as acute angle-closure glaucoma, are much less common.
Symptoms of the different types of glaucoma are explained below.
In cases of chronic glaucoma, there are usually no noticeable symptoms because the condition develops very slowly. People don’t often realise their sight is being damaged because the first part of the eye to be affected is the outer field of vision (peripheral vision). Vision is lost from the outer rim of the eye, slowly working inwards towards the centre.
Changes in vision are often linked to getting older, which is why it is so important to have your eyes checked regularly. You should have an eye test at least every two years.
As a result of these symptoms, some people may also feel sick or be sick. Symptoms of acute glaucoma are not constant. They can last for one or two hours before disappearing again. But each time the symptoms occur, your vision is damaged a little more. It’s important to seek medical attention if you have any of the above symptoms.
It’s possible for the symptoms of glaucoma to be confused with the symptoms of the other condition. For example, uveitis often causes painful eyes and headaches.
Glaucoma is caused by a blockage in part of the eye. This prevents fluid draining out of the eye and increases pressure in the eye, called intraocular pressure.
The eyeball is filled with a watery substance called aqueous humour, which creates pressure in the eye to give it shape. In healthy eyes, this fluid constantly flows in and out of the eye. It drains back into the bloodstream at the same rate that it’s produced to maintain the correct pressure.
Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked, preventing the aqueous humour from draining properly. An obstruction within the eye, such as a blood vessel blocking the trabecular meshwork, can also prevent fluid from draining properly.
When the fluid cannot drain properly, the pressure in the eye builds up and can damage the optic nerve (the nerve that connects the eye to the brain) and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).
It’s often unclear why the drainage tubes become blocked or why other parts of the eye obstruct the tubes.
A relatively common cause of secondary glaucoma is known as pseudoexfoliation glaucoma. This type of glaucoma is caused by the body producing abnormal protein fibres, which can block the flow of fluid out of the eye, leading to glaucoma.
The causes of pseudoexfoliation glaucoma are unclear but most experts think that it is a genetic condition. Pseudoexfoliation glaucoma is treated in the same way as primary glaucoma.
It’s important to have regular eye tests so eye problems, such as glaucoma, can be diagnosed and treated as early as possible. If you have glaucoma, it can take a long time before you realise you have a problem with your eyesight. This is because glaucoma usually damages the outer edge of the eye and works slowly inwards. You may not notice a problem until the glaucoma is near the centre of your eye.
You should have an eye test at least every two years or more frequently if advised by your eye specialist. For example, it may be suggested to you to have more frequent eye tests if you have a close relative with glaucoma, such as a parent, brother or sister.
There are several glaucoma tests that can be carried out. They are painless and quite quick. The tests should be carried out during the same appointment to ensure results are as accurate as possible.
A small amount of anaesthetic (painkilling medication) and dye is placed onto the transparent layer of tissue that covers the front of the eye (your cornea). A blue light from the head of the tonometer is held against your eye to measure the intraocular pressure. Tonometry can diagnose ocular hypertension (OHT – raised pressure in the eye), which is a risk factor for chronic open-angle glaucoma.
Gonioscopy is an examination of the front outer edge of your eye, between the cornea and the iris (the coloured part of your eye). This is the area where the fluid should drain out of your eye. A gonioscopy can help to determine whether this angle is open or closed (blocked).
A visual field test, sometimes called perimetry, checks for missing areas of vision. You will be shown a sequence of light spots and asked which ones you can see. Some dots will appear in your peripheral vision (around the sides of your eyeball), which is where glaucoma begins. If you can’t see the spots in your peripheral vision, it may indicate the glaucoma has damaged your vision.
OCT is an indispensable tool for better eye examination. The OCT gives accurate information about the retina and the macula which are responsible for the delivery of sharp images. With this information your eye doctor can recommend the proper treatment, follow the progress of the disease if any, and assess the effectiveness of the treatment. The test is painless, and quick.
Your optic nerve connects your eye to your brain. Your specialist will use eye drops to enlarge your pupils. Then he / she will examine your eyes using a slit lamp (a microscope with a very bright light) and assess whether your optic nerve has been damaged by the glaucoma. The eye drops used to widen your pupils could affect your ability to drive. You should make alternative arrangements for getting home after your appointment.
Treatment aims to reduce the pressure in the affected eye, called intraocular pressure. Any damage to your vision caused by glaucoma can’t be repaired so it’s important to get an early diagnosis and treatment to prevent further damage.
Laser iridotomy uses a very focused beam of light to create a hole on the outer edge, or rim, of the iris, the coloured part of the eye. This opening allows fluid (aqueous humor) to flow between the anterior chamber, the front part of the eye, and the area behind the iris, the posterior chamber. This opening may decrease pressure in the eye and usually prevents sudden build -up of pressure within the eye, which occurs during an episode of acute closed-angle glaucoma. Some people feel a mild but sharp sensation in the eye during this procedure. But there usually is no pain after laser iridotomy.
A trabeculectomy is the most common type of glaucoma surgery. It involves removing part of the trabecular meshwork to allow fluid to flow through the eye’s drainage system. The procedure will be carried out under local anaesthetic (you are awake) or general anaesthetic (you are unconscious).
If you have been diagnosed with glaucoma your condition will be closely monitored to check for further damage to your vision. Depending on how your glaucoma is progressing, you may need further appointments every one to four months or up to 12-24 months apart.
The main complication of glaucoma is loss of vision that can’t be repaired. This is why early diagnosis and treatment is so important.
If you have surgery to treat glaucoma, there is always a risk of infection. Most infections can be treated with a course of antibiotics. You may also have a reaction to certain types of eye drops.