‘Age-related macular degeneration’ or AMD is a medical condition that causes blurred or reduced central vision in one or both eyes.. AMD is caused by damage to the back of the eye in an area called the macula. The macula is made up of millions of light-sensitive cells that give a person clear, central vision (when they look directly at something straight ahead) and helps them to see fine detail.
There are two forms of AMD depending on how the macula is damaged, ‘dry AMD’ and ‘neovascular AMD’ (also called ‘wet AMD’). Dry AMD is more common, and is found in around nine out of ten patients with AMD. Some signs of dry AMD are waste materials building up under the retina, and the layers of the macula slowly becoming thinner as old cells die and are not replaced by the body. The damage to the macula slowly gets worse and central vision is slowly lost.
Wet AMD is more rare and can cause a person to lose their eyesight much more quickly, sometimes within a few days. Wet AMD is a result of new, unhealthy blood vessels growing under the macula where they would not normally grow. This can often happen in patients who have had dry AMD before, as the body grows new blood vessels to try to fix the problem in dry AMD. The new unhealthy blood vessels can cause swelling and bleeding under the macula, which lead to scarring and loss of vision.
It is not known what causes AMD; however, there are some things that can increase a person’s chances of getting AMD, called ‘risk factors’. These do not mean that a person will definitely get AMD, but they could increase their risk of getting it at some point in their life. Some risk factors are:
People can live with dry AMD for a long time without any symptoms because visual side effects only happen when the AMD is very severe. The main symptom of both types of AMD is a blurred area in the centre of the person’s vision. AMD does not affect the vision around the centre of the eye (known as ‘peripheral vision’) and so it does not cause total blindness. However, the blurred area in the patient’s central vision can grow a lot, affecting everyday activities like seeing faces, reading and driving.
Other symptoms associated with AMD include:
If a person thinks that they have AMD, their eye care professional will examine the eye carefully to make a diagnosis, and will sometimes use photography or imaging of the back of the eye to look for signs of the condition.
When a patient is diagnosed with dry AMD, they might be sent to a specialist at another centre or hospital to get more help. People with dry AMD often need to have a regular test to see if their disease is getting worse. Sometimes, if the AMD is severe, a patient might need to be registered as visually impaired.
As wet AMD can get worse very quickly, patients diagnosed with wet AMD will be sent to see a retinal specialist straight away for further tests or treatment, if it is needed. The tests can include a scan that looks at a cross section of the retina (‘optical coherence tomography’) or a test where a dye is used to stain the blood vessels in the retina so that they can be checked to see if they are leaking fluid (‘fluorescein angiogram’). If the person has wet AMD, they will get treatment straight away.
There are currently no treatments for dry AMD. There is some evidence that not smoking, exercising regularly, eating nutritious food and taking certain supplements may lower the risk of getting AMD, or slow down its development.
The main treatment for wet AMD is a type of drug called ‘VEGF inhibitors’. VEGF is a protein that is involved in making new blood vessels and treatment with VEGF inhibitors stops this process. In wet AMD, VEGF inhibitors can stop new blood vessels growing, stopping more damage to the macula and loss of sight. VEGF inhibitors that are used to treat wet AMD are given as injections into the eye. In most cases of wet AMD, treatment with a VEGF inhibitor stops a person’s vision from getting worse and stops them from becoming blind. In most patients, VEGF inhibitors can improve vision if the person was diagnosed and treated early. However, VEGF inhibitors cannot repair any damage that has already happened.
Current research in AMD is looking at finding treatments for dry AMD as well as other options for wet AMD.