Age-related macular degeneration (AMD) is caused by a problem with the macula in your eye. The macula is the spot at the centre of your retina (the nerve tissue lining the back of your eye).
The macula
The macula is a small spot at the centre of the retina. It is the part of your eye where incoming rays of light are focused. The macula plays an essential role in helping you see things directly in front of you, and is used for close, detailed activities, such as reading and writing.
Dry age-related macular degeneration
As you get older, the layer of tissue that covers your retina can start to break down and become thinner. This means your retina can no longer exchange nutrients and waste products as efficiently as it used to.
Waste products start to build up in your retina and form small deposits, known as drusens. A build-up of drusens, combined with a lack of nutrients, causes the light cells in your macula to become damaged and stop working.
If the light cells in your macula are damaged, your central vision will become blurry and less well-defined.
Wet age-related macular degeneration
In cases of wet AMD, tiny new blood vessels begin to grow underneath the macula.
It is thought these blood vessels form due to a misguided attempt by the body to clear away the waste products from the retina.
Unfortunately the blood vessels form in the wrong place and actually cause more harm than good. They can leak blood and fluid into the eye, which can cause scarring and damage to your macula.
This then causes the more serious symptoms of wet AMD to develop, such as visual distortion and blind spots.
Increased risk
Exactly what triggers the processes that lead to AMD is unclear, but a number things are known to increase the risk factors of developing it. These are described below.
Age
The older a person gets, the more likely they are to develop at least some degree of AMD.
Most cases start developing in people age 55 or over and then rise sharply with age. It is estimated that in people aged 85 or over around 1 in 8 people has AMD.
Family history
Cases of AMD have been known to run in families. If your brother or sister develops AMD, it is estimated your risk of getting it is increased five-fold.
This would suggest certain genes you inherit from your parents may increase your risk of AMD. But exactly what genes are involved and how they are passed through families is unclear.
Smokers
Smoking is a significant risk factor for AMD. In general smokers are 2-3 times more likely to develop AMD than non-smokers.
The longer you have been smoking the greater the risk. Smokers who also have a family history of AMD have an even greater risk.
Gender
Women are more likely to develop AMD than men. This could simply be because women tend to live longer than men.
Ethnicity
Studies have found rates of AMD are highest in white and Chinese people, while lower in black people. This again could be the results of genetics.
Possible risk factors
Alcohol
It is possible that drinking more than four units of alcohol a day over the course of many years may increase your risk of having early AMD. One unit of alcohol is approximately half a pint of standard beer or lager, or one 25ml serving of spirits.
Sunlight
If you are exposed to lots of sunlight during your lifetime, your risk of developing macular degeneration may be increased. To protect yourself, you should wear sunglasses in bright sunlight.
Obesity
Some studies have reported that being obese (very overweight with a body mass index (BMI) of 30 or greater) may double your chance of developing AMD.
High blood pressure and heart disease
There is some limited evidence that having a history of high blood pressure and/or coronary heart disease may increase your risk of developing AMD.
