Macular degeneration, also know as Age-related macular degeneration (AMD), is an eye condition that affects a tiny part of the retina at the back of your eye, which is called the macula. AMD causes problems with your central vision, but does not lead to total loss of sight and is not painful.
AMD affects the vision you use when you’re looking directly at something, for example when you’re reading, looking at photos or watching television. AMD may make this central vision distorted or blurry and, over a period of time, it may cause a blank patch in the centre of your vision.
At the moment, the exact cause for AMD is not known. Some things are thought to increase your chances of developing AMD:
Your age: AMD develops as people grow older and is most often seen in people over the age of 65, although it can develop in people who are in their 40s and 50s, but some think the AMD occuring before 50 is very unusual.
Your gender: more women have AMD than men, probably because women tend to live longer than men.
Your genes: some genes have been identified which seem to be linked to the development of AMD in some people. This has been discovered by looking at families with more than one member who has AMD, but not all AMD is thought to be inherited.
Smoking: smoking greatly increases your risk of developing AMD. Studies also show that stopping smoking can reduce your risk of developing AMD.
Sunlight: some studies suggest that exposure to high levels of sunlight (particularly the UV light contained in sunlight) throughout your life may increase your risk of developing AMD. Wearing sunglasses to protect your eyes from the UV light in sunlight is a good idea for everyone throughout their life.
What you eat: a number of studies have looked at diet as a risk factor for someone developing AMD. At the moment there isn’t agreement on how much of a risk factor diet is. There is some evidence that vitamins A, C and E and zinc may help to slow the progression of AMD in people who already have the condition.
Although you cannot change your age or genes, current thinking is that protecting your eyes from the sun, eating a balanced diet with plenty of fresh fruit and vegetables, and stopping smoking may all help to keep your eyes as healthy as possible.
Unfortunately, because the exact cause of AMD is not known you may develop this condition even if you don’t have any of these risk factors.
Symptoms vary from person to person, but usually the first problems people notice are with their ability to see detail. You may have problems reading small print, even if you wear your usual reading glasses, or you may find that there is a slight smudge in your sight or that your vision has a small blurred area in the centre. Straight lines may look distorted or wavy or as if there’s a little bump in them.
You may also find you become sensitive to bright light or that you see shapes and lights that aren’t actually there. Sometimes people may only notice these changes in one eye.
You should have your eyes tested by an optometrist (optician) if:
- you notice any difficulty with reading small print with your reading glasses
- straight lines start to look wavy or distorted
- your vision isn’t as clear as it used to be.
The optometrist will be able to measure any changes in your vision and examine the back of your eye. If they detect any changes to your macula or any cause for concern they will arrange an appointment with the ophthalmologist (hospital eye consultant) for further tests.
AMD affects the macula area of the retina. The macula is a tiny area of your retina which is very important for seeing detail, colour and things directly in front of you.
When the light enters your eye it is focused onto your retina at the back of your eye. The retina includes a number of layers but the most important for vision is a layer made up of cells called photoreceptors. Photoreceptors are cells which are sensitive to light.
The macula, which is about the size of a pinhead, is a specialised area of the retina that contains a few million specialised photoreceptor cells called cone cells. These cone cells function best in bright light levels and allow you to see fine detail for activities such as reading and writing and to recognise colours.
Away from the central macula is the peripheral retina, composed mostly of the other type of photoreceptor called rod cells. They enable us to see when light is dim and provide peripheral (side) vision outside of the main line of sight. Peripheral vision is the sight you have out of the corner of your eye when looking straight ahead.
When someone develops AMD, the cone cells in the macula area become damaged and stop working as well as they should.
Types of AMD
There are two main types of AMD – “wet” AMD and “dry” AMD. They are called “wet” and “dry” because of what happens inside your eye and what the ophthalmologist (hospital eye doctor) sees when examining the inside of your eye, not because of how the eye feels or whether you have a watery or dry eye.
Dry AMD is the more common type of AMD. It usually develops very slowly and causes a gradual change in your central vision. Dry AMD usually takes a long time, maybe a number of years to get to its final stage. At its worst, dry AMD causes a blank patch in the centre of your vision in both of your eyes. But it doesn’t affect your peripheral vision, so never leads to total blindness.
About 10-15 per cent of people who develop AMD have wet AMD. You develop wet AMD when the cells of the macula stop working correctly and the body starts growing new blood vessels to fix the problem. Unfortunately, these blood vessels grow in the wrong place and cause swelling and bleeding underneath the macula. This new blood vessel growth, medically known as neo-vascularisation, causes more damage to your macula and eventually leads to scarring. Both the new blood vessels and the scarring damages your central vision and may lead to a blank patch in the centre of your sight.
Wet AMD can develop very quickly, making serious changes to your central vision in a short period of time. Treatment is now available for wet AMD, which stops the new blood vessels from growing and damaging your macula. This treatment usually needs to be given quickly before the new blood vessels do too much damage to your macula. If the blood vessels are left to grow, the scarring and the sight loss it causes is usually permanent. Wet AMD doesn’t affect your peripheral vision, so it doesn’t lead to total blindness.
Both types of AMD
Wet and dry AMD have things in common. They usually affect both your eyes, though sometimes one eye may be affected long before the other. Both wet and dry AMD only affect your central vision and won’t affect your vision around the edge of your sight. So neither type of AMD will cause you to lose all your sight.
Some people diagnosed with dry AMD find that, with time, new blood vessels grow and they develop wet AMD. If you have dry AMD and your sight suddenly changes you should always have this checked by your ophthalmologist (hospital eye doctor).
Some people may have wet AMD in one eye and have dry AMD in the other which doesn’t develop into wet AMD. Most people, however, have the same type of AMD in both eyes.
Confusingly, people who have had wet AMD for a long time, causing bad scarring on their retina, may be told that their wet AMD has “dried up”. This usually means that there are no new blood vessels growing and that your macula has been badly scarred. At this stage of wet AMD, the treatments available wouldn’t help.
AMD is not painful and it never leads to a complete loss of vision. Most people with AMD keep their peripheral vision (everything around the edge). This peripheral vision will mean that you should still be able to get around on your own and make use of this vision everyday.