AMD: Prevention is key

"Age-related macular degeneration (AMD) is the most common cause of legal blindness in patients over 55," according to Dr Mina Chung, University of Rochester, New York, USA. "If you look at all people over 65 at least 1 in 10 will have some sign of macular degeneration and 1 in 100 will have severe vision loss and again by some estimates this population is expected to double over the next 25 years."¹

AMD: A variety of forms

The wet form of AMD involves choroidal neovascularization (CNV) and can cause severe vision loss in a very short timeframe, a matter of weeks in some cases. "This form is responsible for about 10% of patients with AMD but causes about 90% of severe vision loss," added Dr Chung.

As a result of the damaging effects of the wet form of AMD a lot of research has been performed in this area and nowadays there are treatments available (e.g., Avastin and Lucentis) that enable specialists to manage patients effectively. However, Prof. Bernstein iterated, "Even with these treatments patients still require monthly injections that are costly so prevention of this disease is still vital."

Nutrients, the macular pigment and current treatments

Epidemiology and animal studies present some evidence that several nutrients can be considered as important for eye health.^2,3 These include antioxidant minerals, vitamins such as A, C and E, which were incorporated into the age-related eye disease study (AREDS), and polyunsaturated fatty acids. There have also been studies describing the importance of the carotenoids, Prof. Bernstein said, "These are thought to be very important because lutein and zeaxanthin are present in high concentrations in the tissues of the eye, in fact, higher than in any other part of the body."

In general, carotenoids enter our systems through our diets. These are then selectively absorbed through our digestion system into the blood stream. After this further specification occurs and in fact only two that are absorbed through diet are found in the eye, lutein and zeaxanthin. "Within the retina itself there is a hundred fold gradient of carotenoid concentrations, which is why you see a yellowish spot, the macular pigment" added Prof. Bernstein. "This appears to protect the retina against some damage from blue light sources."

Work published in 1994, which was a case, controlled study examined lutein and zeaxanthin intake through dietary surveys.⁴ In this work a comparison was made between the amount of lutein and zeaxanthin had been received through diets against the risk of developing AMD. "It was possible to see that the patients who had received the most, at 6 mg per day, had about a 43% reduction in the risk of developing AMD," Prof. Bernstein continued, "This caused a lot of attention and has been driving a lot of further research in the US."

Currently, the treatment of AMD involves intravitreal injections. These are administered monthly until CNV regresses, which can be lengthy, and it is an expensive form of treatment. In addition to this, there are risks associated with injections so nutritional supplements have sparked an interest in the fact that they are inexpensive and safe. Dr Chung added, "Nutritional supplements are extremely safe, the cost is low, they are available in foods that are healthy and they have the potential to approach the population in a preventive way."

So from the work published in 1994 and a further study that was released in 2001 on autopsy eyes, a relationship between levels of lutein and zeaxanthin and AMD has been indicated. According to Prof. Bernstein, "Our current recommendation for management of AMD is the AREDS formulation."