MD causes a hole in the center of vision

Macular degeneration gradually robs millions of older people of their vision. MD occurs when the macula - a highly sensitive light-catching spot in the retina of the eye - fails. Johanna Seddon, of the Massachusetts Eye and Ear Infirmary in Boston, surveyed 12,000 pairs of elderly twins to look at why some people get this incurable condition.

Research has already shown that more than half the cases of the disease are inherited. Seddon and her team wanted to understand what causes the rest. They looked at controllable behaviors, including tobacco use and diet.

"What we found was that both current and past smoking increased the risk for macular degeneration by almost twofold," Seddon reports. "On the other hand, increased intake of fish reduced risk for macular degeneration, particularly for two or more servings per week."

Seddon says the risk was the same even in smokers who'd quit years before. She points to many reasons why smoking might create pathological changes in the delicate architecture of the eye. "It increases oxidative stress in the body - and potentially in the eye, it increases inflammation, and it also affects the circulation and the blood vessels directly."

Johanna Seddon

In contrast, Seddon says, omega 3 fatty acids in oily fish such as salmon and tuna strengthen the eyes and help lower the risk of macular degeneration. She says there's a high concentration of these fatty acids in the retina - the region in the back of the eye where nerves collect and process light. "Another aspect of omega 3 fatty acids is that they can decrease inflammatory response, and they can also improve the endothelial or blood vessel lining function," Seddon notes.

Macular degeneration occurs most often in Caucasians and is the leading cause of blindness in people over the age of 60. Seddon says this research provides yet another reason to not smoke and to eat a healthy diet.