Macular degeneration (AMD) is an age-related disease that affects central vision. It is a gradual death of patches of the central retina responsible for your detail vision. There is currently no effective treatment in the majority of cases, so prevention is critical in order to limit vision loss.
What causes AMD and how can I prevent it?
AMD has 2 forms, dry (90% of cases) and wet (10% of cases). The dry form occurs due to accumulation of metabolic waste products under the central retina. These plaques or “drusen” cause oxidative damage to the surrounding tissue and lead to patchy central vision loss or distortion. Large plaques can weaken the underlying tissue to the point where blood from underneath the retina starts to leak into the retina and cause rapid vision loss (wet macular degeneration).
The dry form increases in incidence with age, with a number of genetic as well as modifiable risk factors. Non-modifiable risk factors include being female, having fair skin and light eye color, moderate to high myopia (near-sightedness), and having an immediate family history. Smoking, lifetime UV exposure and poor diet can contribute to progression because they lead to further oxidation. Based on your risk profile, your optometrist can discuss appropriate preventative strategies. If you have AMD, you may be sent home with a nutrition or supplement plan, along with an “Amsler Grid” to monitor for any changes at home. Advanced or “wet” macular degeneration will cause rapid loss of vision if untreated.
Will vitamins help prevent macular degeneration and is there any harm in taking them?
The largest study ever conducted on the efficacy of vitamin supplements was the AREDS (Age-related eye disease study). It was started when we knew very little about the disease and the protocols and supplements were changed at various points along the way, leading to complex statistical analysis, controversy, and confusion which still exists today. Regardless, this is one of the only evidence based long-term studies we have to draw from. The combination of nutrients used in the study came to be known as the AREDS2 formulation and can be found in numerous commercially available eye vitamins by various manufacturers. There is still much debate on this formulation, especially surrounding the use of zinc (more below).
There have been other smaller studies since, but few concrete recommendations have stemmed from the results. What we do know is that nutrition also plays a large role. Antioxidant and anti-inflammatory nutrients such as Vitamins A, C, E, Zinc and Omega 3 fatty acids play a role in sequestering “free-radicals” which cause oxidative damage. In addition, lutein, zeaxanthin and other carotenoids play a protective role by preventing free-radical formation and oxidative damage. It is important to take any carotenoid supplements in the proper ratio, as they compete with each other for absorption. We have an in-office nutritional survey you can fill out to see if you are getting adequate intake of these nutrients, and if supplementation may be of benefit.
I have heard about genetic testing for AMD, is this something I should consider?
During statistical analysis of the AREDS data, it was noted that AMD progressed faster in some patients who were supplementing with zinc. This lead to speculation that certain people were genetically predisposed to this type of progression and should NOT be taking added Zinc. There is now in-office genetic testing (MaculaRisk® and VitaRisk®) designed to assess both the risk of disease progression, and what combination of supplements would work best. There are conflicting viewpoints on both the validity and implication of these tests, and many leading experts advise against such testing for this reason.
At any rate, the Canadian RDI for Zinc is 9mg/day, and the AREDS study confirmed no difference in efficacy between 25mg and 80mg/day of supplementation. Yet most commercially available AREDS supplements contain 80mg of Zinc per daily dose! Zinc has been implicated in some studies as contributory to heavy metal toxicity and may be associated with a number of diseases, including Alzheimer’s. For this reason, we rarely advise taking supplements higher than 25mg/day.