What is AMD?
Age-related macular degeneration (AMD) is a disease of the macula, the central part of the retina in the eye, that results in loss of central vision. There are two types of AMD: early and late. Early AMD can be present in the eye without the sufferer being aware of it, as it has no symptoms that can be detected by the human eye.
Early AMD often progresses into late AMD, and this becomes visually consequential; in order words, it affects vision. The earlier AMD is diagnosed, the easier it is to intervene.
What happens if you have AMD?
AMD is particularly frustrating because (if untreated or untreatable) it results in a loss of central vision. In other words, someone with AMD can see everything except what he/she is directly looking at, and is therefore unable to read, watch TV, recognise faces or drive. Late AMD dramatically reduces an individual’s quality of life.
What causes AMD?
Although the exact cause of AMD remains uncertain, it is known that damage by free radicals within the eye plays a crucial role. Free radicals are unstable molecules, and are produced when we use oxygen, and when light enters the eye. Because we use oxygen when we breathe, and because we need light to see, damage caused by free radicals is unavoidable.
What are the symptoms of AMD?
The main symptom of visually consequential AMD (AMD which affects vision) is dim, fuzzy or distorted central vision, which can affect the ability to carry out fine detail visual tasks such as reading. With this disease, objects may appear distorted or smaller than they really are. Faces will become more difficult to recognise. As the disease progresses, central vision is totally lost. However, good peripheral (side) vision is retained.
Risk Factors of AMD
1. Genetic Status
Two genes in particular have been strongly identified with increased risk of developing AMD. These are complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) genes. These were identified in 2005 as being the major risk genes for AMD, which together have been estimated to account for over 50% of risk for developing AMD.
2. Family history of visually consequential AMD
Family history of late AMD is one of the most important and established risk factors for this condition. In fact, people with a first degree relative (i.e. a parent or sibling) with late AMD are believed to be three times more likely to develop late AMD than someone without a confirmed family history of disease.
3. Cigarette smoking
Cigarette smoking is one of the most important risk factors for late AMD. The risk of a current smoker developing late AMD is two to three times greater than someone who has never smoked.
4. Poor diet
Current research has shown that a healthy diet is an important for reducing risk of AMD. In particular, foods containing the macular carotenoids are believed to be important in helping to prevent the onset of late AMD.
5. Inadequate intake of anti-oxidant supplements
Anti-oxidant supplements have been shown to be beneficial in reducing the progression of AMD that has not yet affected vision from developing into AMD that does affect vision. There is also a growing body of evidence that anti-oxidant supplements containing the macular carotenoids may be beneficial in terms of preventing or delaying the onset or progression of AMD.
White race is associated with increased risk of late AMD, reflected in the fact that the prevalence of this disease is far greater in white populations when compared to non-white populations. However, the prevalence of late AMD is on the increase in non-white populations, probably due to the fact that western lifestyle habits (e.g. nutritionally-poor diet and sedentary lifestyle) are becoming more common worldwide.
Obesity is a suggested risk factor for late AMD. In fact, there appears to be a growing body of evidence in support of the view that obesity is an important determinant for the development of late AMD.
Females are believed to be at greater risk of AMD than males, and the link between female sex and development of late AMD is believed to be hormone-related (i.e. oestrogen-related). However, the evidence available is not conclusive, and the greater prevalence of late AMD in females may be due to the fact that females live longer.
9. Cumulative exposure to visible light
Cumulative exposure to visible light is a suggested risk factor for late AMD.
10. High cholesterol levels
High cholesterol is a suggested risk factor for late AMD. However, the results of various studies investigating a possible link between hypercholesterolaemia (i.e. an excess of cholesterol in the blood) and AMD are not conclusive.
Hypertension, or high blood pressure, is a suggested risk factor for late AMD. However, the results of studies to date remain inconclusive.
The condition of diabetes can increase the risk of developing late stage AMD. This risk is associated with angiogenesis (new vessel growth) in the diabetic retina.The risk is greatest in poorly controlled Type 2 diabetes (late onset, largely diet- and medication-controlled). Type 1 diabetics (young-age onset, insulin-controlled) are at less risk. However, control in these individuals is also important.