Free Radicals Can Damage Retinal Cells

By Mahmood Piraee –

Free Radical Damage to Retinal Cells Can Increase the Risk of Developing 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. Progression of AMD causes gradual blurring of central vision that is needed for tasks such as reading, watching TV, writing, driving, doing close work or recognising faces.

Macular degeneration is painless and therefore detection of the disease may occur long after its initial development.

AMD hits people aged 50 upwards and it is estimated that there are over 20 million cases of AMD in the US and Europe.

In the UK more than 500,000 people are affected by AMD, and 26,000 new cases are diagnosed every year, with annual cost estimated at £1.7 billion in 2010. In Canada is estimated that between 17,000 and 24,000 new cases are diagnosed each year. In Australia one in seven people over the age of 50 are affected by the disease.

However, general awareness of AMD and risk factors involved is alarmingly low, and the disease 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.

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

Over the years retina become particularly vulnerable to damage from oxidative stress, and our body’s ability to repair the damages declines as we age.

Vision loss in patients with AMD is attributable to oxidative damage and possibly inflammation resulting in photoreceptors’ death in central retina. By progression of AMD, a build up of cellular wastes occur underneath the retinal cells, which your eye doctor can detect them as yellow spots called ‘drusen’. Presence of drusen is an early sign of developing AMD, while it may not affect your vision at the early stage it increases the chance of developing AMD over the years.

Consumption of saturated fats, and particularly smoking which reduces the protective effect of antioxidants, increase the risk of developing AMD.

Retinal cells are highly sensitive to oxidative damage from sunlight because of high consumption of oxygen, the transparency of the cornea and lens that allow continuous exposure of retina to light. Light damage can lead to macular degeneration, and that is why people with light-coloured eyes need to be more vigilant in protecting their eyes from direct sunlight.

AMD 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, which results in gradual loss of central vision, but it could also develop to more aggressive wet form.

Wet AMD:
In wet AMD the blood vessels grow into retina, which then leak 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.

It is therefore, important to consult with your eye doctor if you notice any sudden change in your vision or any visual symptom.

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

 

 

 

 

 

 

 

 

Directions
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.

 

 

 

 

Normal vision

 

 

 

 

Consult your eye doctor immediately

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

Risk factors:
Risk factors affecting development of AMD include:
– Age greater than 50 is the number one risk factor in AMD
– Caucasian race
– Family history; Consult your eye doctor if you have family history of AMD.
– Smoking can reduce the protective effect of antioxidants in the eye and almost triples the risk of developing AMD. Stopping smoking can reduce the risk of developing AMD.
– Extended exposure to light.
– Atherosclerotic vascular disease, and consumption of saturated fats, high blood cholesterol, and high blood pressure.
– Low level of daily exercise.
– Nutritional deficiency and lifestyle factors. There is a large body of scientific evidence for eye health benefits of nutritional supplements containing plant extracts, antioxidant vitamins and minerals for reducing the risk of vision loss in AMD.

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
– Consume a handful of nuts at least once a week.
– Adjust alcohol intake to recommended daily levels.

It is important to note that early stages of AMD are usually without symptoms. Therefore, a comprehensive eye exam by an eye doctor is needed for diagnosis of early AMD. Blurred vision and difficulty recognising faces are most common symptoms of dry AMD.

We recommend regular eye exams at least every two years. Engage family and friends, or seek professional counselling if you are affected by AMD or known to be at high risk of developing AMD.

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 risks involved in developing AMD, in later life.

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/

Mahmood Pieree is a qualified pharmacist (Shahid Beheshti University of Medical Sciences, Tehran) and subsequently completed his PhD in molecular and cellular biology (Dalhousie University, Halifax, Canada) and was then engaged in research management and business development in leading international biotech companies in natural products drug discovery and development (Ecopia Biosciences (now Thallion Pharma), Montreal, Canada, and Biotica Technology Ltd., Cambridge, UK) prior to co-founding Persavita Ltd. At Persavita he works on developing and commercializing science-based nutritional supplements for age-related health changes. He is also co-inventor on several patents/patent applications, and is also co-author on several peer-reviewed publications. He lives in Cambridge, United Kingdom.