Age-related macular degeneration (AMD)

Age-related macular degeneration (AMD)

Age-related macular degeneration (AMD) is the leading cause of adult vision loss in developed countries and accounts for more than 50% of blindness in the United States.

AMD gradually destroys the macula which is a tiny part of retina responsible for sharp and central vision. The rest of the retina is called peripheral retina, and is used to see general shapes and gives you side vision or peripheral vision. Macular degeneration is painless and therefore detection of the disease may occur long after its initial development.

In patients affected by Age-related macular degeneration (AMD), macular cells slowly break down by progression of the disease, gradually blurring central vision that is needed for tasks such as reading, watching TV, writing, driving, doing close work or recognising faces.

It is estimated that there are over 20 million cases of AMD in the US and Europe, and up to 17 million elderly in the US have at least early signs of AMD called Age Related Maculopathy (ARM). About 10 million individuals in the United States are affected with age-related macular degeneration (AMD) disease, with more than 1.8 million of them suffering from the more advanced stages of the disease, and this figure is expected to increase by more than 50% to almost 3 million in 2020.

Across the world about one in ten people over the age of 60 years is affected with AMD. The worldwide incidence increases to more than 1 in 4 in people over the age of 75 years.

In the UK, for example, AMD affects a quarter of population over the age of 60 years, and more than half of people at age 75 years or older. The total number of estimated UK AMD cases stands at around 500,000, with 26,000 new cases of the disease confirmed every year. However, 26,000 may represent only a fraction of cases diagnosed.

However, general awareness of AMD and risk factors involved is alarmingly low in the UK. In a national survey, only 16% of respondents were familiar with the debilitating eye condition. This is despite the fact that AMD is the leading cause of vision loss in the UK among elderly population, and it is likely that it contributes significantly to the total cost of vision loss which stands at over £4.9 billion per year.

According to recent estimated the number of people with vision loss from age-related macular degeneration (AMD) will increase by about 31% from 2010 to 2020. The total estimated UK cost for AMD for the decade from 2010 to 2020 stands at £16.4 billion.

In other parts of the world age-related macular degeneration (AMD) has high prevalence. It is estimated that between 17,000 and 24,000 new patients are diagnosed in Canada with age-related macular degeneration (AMD) each year. In Australia one in seven people over the age of 50 are affected by the disease.

AMD is becoming a major public health concern because the population is aging and an increase in incidence is expected. The resulting visual impairment affects patients’ quality of life, emotional and social health, as well as independence. Individuals affected become increasingly dependant on care-providers for daily activities, and some patients may also experience depression.

Although vision loss is becoming a major public health problem, current therapy options for age-related macular degeneration (AMD) are limited. There is no cure or treatment for  age-related macular degeneration (AMD) but depending on the stage and type of the disease (wet or dry) treatment options are available that can help slow down disease progression. For people at risk of developing age-related macular degeneration (AMD) regular eye test is important because the earlier the disease is detected, the more vision you are likely to retain.

Symptoms of age-related macular degeneration (AMD) :
Symptoms vary from person to person, but usually the first problems people notice is with their visual performance, specifically with the ability to see fine details.
– you may have problems reading small prints, even after wearing your regular reading glasses, or
– you may find that there is a slight fog or smudge in your sight
– you may find that there is a small blurred area in the center of your vision.
– straight lines may look distorted or wavy or as if there’s a little bump in them.
– your eyes may become sensitive to bright light or that you see shadows and lights that aren’t actually there.
These changes in some people may only happen in one eye.
It is important to visit your eye doctor, optometrist (optician) if :
– you notice any difficulty reading small prints with your usual reading glasses
– straight lines start to appear wavy or distorted
– your vision isn’t as clear as it used to be

Pathology of age-related macular degeneration (AMD):   

Vision loss in patients with age-related macular degeneration (AMD) is attributable to photoreceptors death in central retina. Current research suggests a role for damage to retinal pigment epithelial (RPE) cells, a layer of cells underneath the retina, caused by oxidative stress and possibly inflammation, leading to photoreceptor death. The main function of RPE is to nourish retinal cells, and remove waste products and deliver them to the choroid, which is the network of blood vessels underneath. RPE separates retina from the choroid.

By progression of age-related macular degeneration (AMD) , a build up of these cellular wastes occur underneath the RPE. Your eye doctor upon examining the retina can see these waste products which appear as yellow spots called ‘drusen’. Presence of drusen is an early sign of developing AMD, while this may not affect your vision at the early stages. This is why it is important to have your eyes and particularly macula of the eye examined by an eye doctor. Small amounts of drusen increase the chance of developing age-related macular degeneration (AMD) over the years.

Normal metabolism in our body produces unstable molecules called free radicals which can damage cellular components including those in retinal cells. Antioxidants are useful nutrients found in a healthy and varied diet hat help our body fight the damaging effects of free radicals. We might not obtain sufficient levels of antioxidants from diet, and this may increase the risk of developing AMD.

Consumption of saturated fats, and particularly smoking which reduces the protective effect of antioxidants, increase the risk of developing age-related macular degeneration (AMD) .

Additionally, the cells in the retina are highly sensitive to light because of its high consumption of oxygen, the transparency of the cornea, aqueous humour and lens that allow continuous exposure of retina to light. This creates an intrinsic vulnerability of the retina to damage via photo-oxidative stress, which can lead to macular degeneration. This is why people with light-coloured eyes may be more sensitive to damage from sunlight.

Over the years retina become particularly vulnerable to damage from oxidative stress from different sources, and our body’s ability to repair the damages declines as we age. This leads to degeneration of RPE cells and loss of their function, resulting in photoreceptor death and visual impairment.

Age-related macular degeneration is classified as dry  Age-related macular degeneration (dry AMD) , and wet AMD:

Dry AMD: 

Dry AMD is the most prevalent form (90%) among the patients afflicted with the disease.

When RPE cells die, the retinal calls above them also die, leading to patches of retinal ‘scar’, commonly known as geographic dystrophy or dry AMD, which is the slow form of the disease. Dry AMD causes gradual loss of vision, but it could develop to more aggressive wet form.

Wet AMD:

In wet AMD the RPE cells lose their ability for separating choroidal blood vessels from retinal cells, and as a consequence the blood vessels grow into retina, which then leak blood and fluid into the retina. Wet AMD affects 10% of patients, and is the most severe form of the disease leading to rapid loss of vision. Fortunately treatment options are available for wet AMD, but early diagnosis and early start of treatment are essential to help slow down the progression of vision loss. In Australia, 17,000 new cases of wet AMD are diagnosed each year.

It is therefore, important to consult with your eye doctor if you notice any sudden change in your vision or any visual symptom. With an early detection of the disease and early treatment you will have a better chance of avoiding vision loss from age-related macular degeneration (AMD) .

The Amsler grid test is a useful tool to use regularly to test for possible symptoms of age-related macular degeneration (AMD) or sudden changes in vision.

isk factors involved in developing age-related macular degeneration:

Risk factors affecting development of age-related macular degeneration (AMD) include:
– Age greater than 50 is the number one risk factor in AMD

The graph below shows the prevalence of age-related macular degeneration (AMD) among adults 40 years and older in the United States, indicating that age is a main risk factor for developing AMD.

Data from http://www.nei.nih.gov/eyedata/pbd_tables.asp

Other risk factors:
– Caucasian race
– Genes: some genes have been identified which seem to be linked to a higher risk of developing age-related macular degeneration (AMD) in some people. This has been discovered by looking at families with more than one member who has AMD. However not all cases of AMD is thought to be inherited.
– Gender: more women have age-related macular degeneration (AMD) than men, and this is perhaps because women tend to live longer than men.
– Family history of age-related macular degeneration (AMD) ; it is very important to know if your family has history of eye diseases and let your eye doctor know, so that they are aware of the condition. People who have a parent or sibling with AMD are at a higher risk of developing it themselves. But that doesn’t mean that you shouldn’t take precautions and have regular eye exams to manage your own risk.
– Smoking, Research has confirmed the harmful effects of smoking on eyesight, and consequently stopping smoking can reduce the risk of developing age-related macular degeneration (AMD) . Smoking can reduce the protective effect of antioxidants in the eye, and almost triples the risk of developing AMD. According to reports from AMD Alliance, in the UK an estimated 54,000 people have AMD as a result of smoking.

– People with fairer skin and blue or green eyes have a higher risk of developing AMD and cataracts as a result of repeated exposure to ultra violet (UV) light from the sun. Take precautions to limit your exposure to the sun by wearing sunglasses with at least 99% UVA/UVB protection.

Further risk factors include:
– Extended exposure to blue light, either from sunlight or long-term exposure to computer monitors. Protecting your eyes from sun exposure by wearing sunglasses is important any time of year, even in winter and on overcast days. Research indicates that there may be a link between sun exposure and the development of both age-related macular degeneration (AMD) and cataracts. Wear sunglasses with at least 99% UVA/UVB protection.
– Atherosclerotic vascular disease, and consumption of saturated fats and high blood cholesterol, and high blood pressure.

– Nutritional deficiency and lifestyle factors such as lack of daily exercising. Your risk of both age-related macular degeneration (AMD) and diabetic retinopathy can be reduced through good nutrition. Fresh fruits and dark leafy green vegetables may also help prevent AMD. Good nutrition can also help to control your blood sugar and thereby decrease the risk of diabetic retinopathy.

– Obesity may increase the risk of developing dry  age-related macular degeneration (dry AMD) .  The increase in the risk of developing dry AMD, associated with being overweight or obese, varies between a 1.5 times increased risk (for people with a BMI of over 25) and doubling of the risk (for people with a BMI of over 30) compared with that of a person who is not overweight. More significantly still is the fact that obesity appears to increase the rate of progression of wet AMD, the type of AMD that can lead to severe sight loss and legal blindness within as little as three months.

People with a BMI of over 25 double their risk of experiencing a rapid progression of
the disease.

Furthermore, there is evidence that people who have a genetic predisposition for developing AMD (ie who have a gene defect that has been linked with AMD) need to be particularly careful to avoid weight gain since their risk increases from a four fold risk with normal weight to an eleven fold risk if they are obese.

Age-related macular degeneration (AMD) is a disease of aging, but it should not be considered a natural and inevitable consequence of it. Intervention by nutritional supplementation is available for dry AMD, and adoption of a healthy lifestyle and varied diet can help reduce the risk of developing AMD.

Role of nutrition in age-related macular degeneration (AMD) & effect of vitamins in macular degeneration

Because  age-related macular degeneration (AMD) is primarily a disease of the elderly, interventions that prevent or delay disease onset would have significant effect on reducing the social and economical burden of this debilitating disease.

The role of nutritional supplementation in delaying the onset or progression of ocular disease, and particularly  age-related macular degeneration (AMD) is of utmost interest to healthcare professionals and patients. There is a large body of scientific evidence for eye health benefits of nutritional supplements for reducing the risk of vision loss in AMD.

A leading clinical study called the Age-Related Eye Disease Study (AREDS) found that combination of antioxidant vitamins and minerals (vitamins C and E, beta-carotene (pro-vitamin A), zinc, and copper) can slow the progression of AMD in some people. Nutritional supplementation reduced the risk of progression to advanced AMD.  In United States nutritional supplementation with the combination of antioxidative vitamins and mineral could save more than 300,000 people from vision loss over the five year period between 2006 to 2011.

Evidence from many clinical studies for eye health benefits of nutritional supplements has created a hope and constant need for development of novel remedies and therapeutics to ameliorate dry AMD and decelerate its progress by aging.

The following recommendations promote a healthy living lifestyle, and may have an impact on development and/or progression of AMD:
– Avoid smoking
– Daily exercising
– Maintaining normal blood pressure and cholesterol levels
– Protect eye from intense light, e.g., midday sun
– Adopt a healthy lifestyle and varied diet rich in fish, green and leafy vegetables
– Adjust alcohol intake to recommended daily levels.

It is important to note that early and intermediate stages of   age-related macular degeneration (AMD)  are usually without symptoms. Therefore, a comprehensive dilated eye exam by an eye care professional is needed for diagnosis of early AMD. The eye examination may include tests for measuring visual acuity, dilated eye exam to assess the health of retina, Amsler grid test, and fluorescein angiogram to identify wet AMD. Blurred vision and difficulty recognising faces are most common symptoms of dry AMD.

We recommend regular eye exams at least every two years, and following a healthy lifestyle and varied diet.  Engage family and friends, or seek professional counselling if you are affected by   age-related macular degeneration (AMD) or known to be at high risk of developing AMD.

Also a note that people who take certain vitamins may experience a reduced risk of developing the advanced stage of macular degeneration. High-dose formulas can contain antioxidants, carotenoids lutein, zeaxanthin, antioxidant minerals such as zinc.
Vitamins for macular degeneration may help people who are at high risk for developing advanced macular degeneration keep their vision.
References:
– Huang et al. (2008). Oral supplementation of lutein/zeaxanthin and omega-3 long chain polyunsaturated fatty acids in persons aged 60 years or older, with or without AMD. Invest. Ophthalmol. Vis. Sci. 49:3864-69.
– http://www.rnib.org.uk
– http://www.amdalliance.or g
– http://www.ahpo.org
– http://www.nutrition.org.uk
– Brown et al. (2005). Age-related macular degeneration: economic burden and value-based medicine analysis.  Can Jour Ophthalmol 2005; 40: 277–87.
– Bartlett H, Eperjesi F. (2004). Dietary analysis and patterns of nutritional supplement use in normal and age-related macular disease affected subjects: a prospective cross-sectional study. Nutrition Journal 3:16. doi: 10.1186/1475-2891-3-16.

– Chakravarthy et al. (2010). Clinical risk factors for age-related macular degeneration: a systematic review and meta-analysis. doi:10.1186/1471-2415-10-31
– DeBlack SS. (2003). Cigarette smoking as a risk factor for cataract and age-related macular degeneration: a review of the literature. Optometry 74:99-110.
Barker FM 2nd. (2010). Dietary supplementation: effects on visual performance and occurrence of AMD and cataracts. Current Medical Research & Opinion 26:2011–2023.
– Connell et al. (2009). Risk Factors for Age-Related Maculopathy. doi:10.1155/2009/360764

– Schaumberg, DA et al., Multiplicative relationship between risk factors for AMD reported at 2006 Annual ARVO meeting
– http://www.nei.nih.gov
– http://www.mdfoundation.com.au