More than eight million people in the U.S., predominantly women, suffer from dry eye syndrome, a painful and debilitating eye disease. In the first study of its kind to examine modifiable risk factors, researchers from Brigham and Women's Hospital (BWH) and Schepens Eye Research Institute (SERI) found that the amount, type and ratio of essential fatty acids in the diet may play a key role in dry eye prevention in women. The study is published in the October 2005 issue of the American Journal of Clinical Nutrition.

According to lead author Biljana Miljanovic, MD, of the Divisions of Preventive Medicine and Aging at BWH, "Dry eye syndrome impacts quality of life, productivity and safety for millions of people. Unfortunately, there is little advice clinicians can offer about its prevention. Our study set out to examine how changing dietary habits in America, primarily a shift in the balance of essential fatty acids we are consuming, may be associated with onset of this eye disease. We found that a high intake of omega-3 fatty acids, often referred to as a 'good' fat, commonly found in fish and walnuts, is associated with a protective effect. Conversely, a higher ratio of omega-6, a fat found in many cooking and salad oils and animal meats, compared to omega-3 in the diet, may increase the risk of dry eye syndrome."

Dry eye syndrome is characterized by a decline in the quality or quantity of tears that normally bathe the eye to keep it moist and functioning well. The condition causes symptoms such as pain, irritation, dryness and/or a sandy or gritty sensation. If untreated, severe dry eye syndrome can eventually lead to scarring or ulceration of the cornea, and loss of vision. Victims can experience symptoms so constant and severe that reading, driving, working and participating in other vision-related activities of daily life are difficult or impossible.

In this study, the researchers report the following specific findings:

- Women with the highest levels of omega-3 in their diets reduced their risk of dry eye syndrome by 20% compared to women with the lowest levels of this fat in their diet.

- A dietary ratio of omega-6 to omega-3 greater than 15:1 was associated with a 2.5-fold increased risk of dry eye syndrome in women. Currently, the average American diet consists of a similarly high ratio of omega-6 to omega-3 fatty acids.

- Tuna consumption reduced the risk of dry eye syndrome. Women who reported eating at least five servings of tuna per week had a 68% reduced risk of dry eye syndrome compared to women who consumed one serving per week.

- Other fish types that have lower levels of omega-3 fatty acids did not appear to protect against dry eye syndrome.

"We are accustomed to the mantra 'you are what you eat,' and our study suggests that this also applies to a person's vision," said Debra Schaumberg, ScD, OD, MPH, the senior author of the study, clinical associate scientist at SERI and associate epidemiologist at BWH. "Based on this report, preventing dry eye syndrome is another potential reason to follow a diet rich in tuna and other foods plentiful in omega-3 fatty acids."

These findings are based on surveys completed by more than 37,000 women enrolled in the landmark, BWH-based Women's Health Study. Survey questions were designed to elicit information about an individual's history of diagnosed dry eye syndrome and dietary habits.