Eyes

The macula is the central portion of the retina that is responsible for transforming light entering the eye into electrical neural impulses. The macula mediates central vision as well as the ability to see colour and fine detail. Macular degeneration results in improper processing of images. Age-Related Macular Degeneration (AMD) is the leading cause of blindness in people over 60 in the western world. It is estimated that 1.6% of the population in the 50 to 65 year-old age group is affected, rising to 30% in the over 75 year-old age group.

Heredity and aging appear to represent the primary risk factors; however, long-term exposure to blue and ultraviolet light may also contribute. Women and individuals with lighter coloured eyes may be at greater risk. Low circulating levels of antioxidants such as Vitamins A, C and E may be associated with a higher risk and thus oxidative damage may play a role. Hyperlipidaemia (high cholesterol levels), high consumption of saturated fat and cigarette smoking have also been implicated. The disease generally takes one of two forms. In both forms, central vision is primarily affected, while peripheral vision is preserved. The “dry” form results from thinning of the macula tissue.

Symptoms include greyness, haziness or a blind spot in the centre of the visual field. Blurring of words and dimming of colours are often reported. The “wet” form results from abnormal blood vessel growth beneath the retina, resulting in distortion of the macula. Vascular leakage may also result in retinal damage. Visual distortions, such as a wavering of straight lines and a central blind spot are characteristic symptoms. The “dry” form is generally less severe, developing more slowly than its counterpart. It accounts for up to 90% of cases. Treatment does not appear to reverse damage; however, vision loss may be slowed. The wet form may respond to laser treatment in about 50% of the people treated; however, the effects may be temporary. The dry form does not respond to surgical correction.

Appropriate nutrition, smoking cessation, and protective measures such as wearing sunglasses that block out ultraviolet light, are important adjunctive measures. Nutrients associated with improving the integrity of collagen tissues may also be beneficial. Carotenoids are antioxidant substances found in high levels in many green and coloured vegetables. There is increasing evidence in the literature to suggest that the carotenoids lutein and zeaxanthin may play a role in modulating the course of age-related macular degeneration.