A 20-year study of women in the Nurses’ Health Study has shown that Type 2 diabetes is associated with primary open angle glaucoma (POAG), the most common form of glaucoma, accounting for about 60 to 70% of all glaucomas.

The study is published in the July issue of the journal Ophthalmology.

Researchers at the Massachusetts Eye and Ear Infirmary, Brigham and Women’s Hospital, Harvard School of Public Health and Harvard Medical School observed 76,3128 women who were enrolled in the Nurses’ Health Study from 1980 to 2000.

Eligible participants were at least 40 years old, did not have POAG at the beginning of the study, and reported receiving eye exams during follow-up. After controlling for age, race, hypertension, body mass index, physical activity, alcohol intake, smoking and family history of glaucoma, they found that type 2 diabetes was positively associated with POAG. However, the relation between type 2 diabetes and POAG did not increase with longer durations of type 2 diabetes.

“The study supports the notion that type 2 diabetes is associated with an increased risk of glaucoma,” said Louis Pasquale, M.D., lead author of the study and co-director of the Glaucoma Service at the Massachusetts Eye and Ear Infirmary (MEEI) and an Assistant Professor of Ophthalmology at Harvard Medical School. “While obesity fuels the type 2 diabetes epidemic, it appears that factors unrelated to obesity contribute to the positive association between type 2 diabetes and glaucoma. We were surprised to find this. Our study had a large enough sample to allow us to focus on type 2 diabetes only and to study its relation to newly diagnosed POAG cases. We were also able to correct for other factors that could contribute to glaucoma. Our work suggests, but in now way proves, that factors other than lifestyle behavior contributing to insulin resistance could lead to elevated intraocular pressure and glaucoma.”

According to the National Eye Institute, POAG affects more than 2 million individuals in the United States and is one of the leading causes of blindness. With the rapid aging of the U.S. population, the number of individuals affected by the disease will increase to more than 3 million by 2020.

The study suggests that people with type 2 diabetes should be screened for glaucoma. As of 2002, Medicare provides coverage for glaucoma screenings in beneficiaries with diabetes, helping to enhance access for this group who may be at risk for visual loss from POAG.

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