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[09/12/2011] 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 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 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 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 AMD has high prevalence. It is estimated that between 17,000 and 24,000 new patients are diagnosed in Canada with 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 AMD are limited. There is no cure for 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 AMD regular eye test is important because the earlier the disease is detected, the more vision you are likely to retain.

Pathology of age-related macular degeneration:   

Vision loss in patients with 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 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 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 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 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 AMD.

The Amsler grid test is a useful tool to use regularly to test for possible symptoms of AMD or sudden changes in vision.

 
Amsler Grid test

 Amsler grid- Test for AMD symptoms
 
Directions fo using Amsler grid test:
1. Do not remove glasses or contact lenses you normally wear for reading.
2. Hold the grid approximately 40cm from your face in a well-lit room.                                                                                           

3. Cover one eye with your hand and focus on the centre dot with your uncovered eye. Repeat with the other eye.
4. If you see distorted or wavy lines, or blurred or missing areas of vision, you may be displaying symptoms of AMD and should contact your eye doctor immediately.

 

Amsler test- normal vision

 

 

 

 

 

Normal vision

 

Amsler grid- AMD symptom

 

 

Consult your eye doctor immediately

 

 

Note: DO NOT depend on this grid for any diagnosis.

Risk factors involved in developing age-related macular degeneration:

Risk factors affecting development of AMD include:
-          Age greater than 50 is the number one risk factor in AMD
 
The graph below shows the prevalence of AMD among adults 40 years and older in the United States, indicating that age is a main risk factor for developing AMD.
Age-related macular degeneration AMD prevalence -Statistics

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

Other risk factors:
-          Caucasian race
-          Family history of 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.
-          Smoking, Research has confirmed the harmful effects of smoking on eyesight, and consequently stopping smoking can reduce the risk of developing 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.

Further risk factors include:
-          Extended exposure to blue light, either from sunlight or long-term exposure to computer monitors.
-         Atherosclerotic vascular disease, and consumption of saturated fats and high blood cholesterol, and high blood pressure.
-         Nutritional deficiency and lifestyle factors such as daily exercise

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 & effect of vitamins in macular degeneration

Because 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 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 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 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.org
- 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
- http://www.nei.nih.gov
- http://www.mdfoundation.com.au
 



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[15/04/2011] Eye Health Recommendations

[09/12/2011] Healthy lifestyle is associated with lower risk of developing age-related macular degeneration

[09/12/2011] Lutein and Zeaxanthin for age-related macular degeneration (AMD)

[09/12/2011] Saffron for Age-related Macular Degeneration- Eye care & Eye Health

[15/02/2012] Mechanism of action of resveratrol, NIH study.

[16/08/2012] New clinical study confirms the eye health benefits of saffron in age-related macular degeneration (AMD)

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[23/06/2013] Saffron administration prevents selenite-induced cataractogenesis.

[23/06/2013] Eye health and food supplements

[23/06/2013] Smoking and risk of age-related macular degeneration (AMD)

[23/06/2013] Eye exam and prevention of vision loss

[17/10/2013] Clinical management of early AMD patients with saffron supplementation is easier now, as the effects are independent of CFH and ARMS2 genetic variations.

[18/10/2013] Scientific information behind the development of Saffron 2020

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[31/08/2014] Macular Society members are not eating enough lutein according to a new study.

[31/08/2014] CAN SMOKING REALLY MAKE YOU GO BLIND?


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