The Picture of Health

One of the most common degenerative eye diseases is age-related macular degeneration (AMD). AMD affects approximately 1 million Canadians and is the leading cause of non-reversible vision loss in Canada. The exact cause of AMD is unknown, but risk factors include age, smoking, obesity, high blood pressure, and a diet low in omega-3s and plant-based antioxidants.

Clearly, agents that can modify the course of this disease are of high therapeutic importance and present the opportunity to improve the lives of many.

Antioxidants and zinc

In a landmark randomized controlled trial over six years, researchers studied the effect of antioxidants (vitamins C and E and beta carotene) plus zinc on the progression of AMD. Of the 3,640 participants, those who supplemented with both had a reduced risk of developing advanced AMD by almost 30 percent, with a similar reduction in the rates of moderate visual acuity loss. Patients who received either zinc alone or antioxidants alone did not experience this benefit, suggesting that these essential nutrients are effective synergistically when administered together.

Eye-specific antioxidants

Lutein and zeaxanthin are eye-specific antioxidants. They are naturally occurring constituents of the retinal pigment and play crucial roles in protecting the retina from the damaging effects of sunlight as well as metabolic and biochemical factors. Lutein supplementation has been shown to increase macular pigment density and prevent worsening of visual acuity in early AMD. A combination of lutein and zeaxanthin has also been shown to significantly improve several measures of visual function.

Fatty acids

Higher intake of fish and omega-3 fatty acids reduces risk of AMD. DHA is a structural component of photoreceptors in the retina, while EPA and DHA together increase levels of good cholesterol (HDL), which is a transporter of lutein into the retina. This beautiful mechanism underscores, once again, the importance of fish-derived omega-3 fatty acids.

Melatonin

Melatonin is a novel agent for AMD. Melatonin occurs naturally in the retina, where it exerts antioxidant effects. An early study of patients with AMD found that taking 3 mg of melatonin dramatically reduced the degenerative changes that could be seen on the retina itself and stabilized visual acuity. The authors concluded that melatonin may be useful in preventing or delaying AMD.

Natural agents including antioxidants, lutein, zeaxanthin, zinc, omega-3 fatty acids, and melatonin are among the few existing therapies for degenerative eye disease. These agents represent important interventions for preventing and limiting eye disease among those 50 years of age and older.