Were you ever on the Pill…or has a woman you love ever taken oral contraceptives? If so, you need to know about worrisome new research that links a history of birth control pill use to an increased risk for glaucoma, a very serious eye disease.

Second only to cataracts, glaucoma is a leading cause of blindness. The condition, which is characterized by excessive pressure inside the eye, eventually can cause irreversible damage to the optic nerve. And it’s very common, affecting upwards of two million adults in the US. Women are more than 50% more likely than men to develop this disease…so for a new study, researchers went looking for factors related to gender that could affect glaucoma risk.

The researchers drew upon data from the ongoing National Health and Nutrition Examination Survey, extracting information on 3,406 women age 40 and up. All the women completed questionnaires about their reproductive health, including number of pregnancies, ages at which their periods started and stopped, history of oral contraceptive use and history of hormone replacement therapy use. They also answered questions about their vision, including whether they had ever been told that they had glaucoma. After adjusting for age, general health conditions, socioeconomic status and other factors known to affect glaucoma risk, the researchers analyzed the data.

Their disturbing finding: Women who had used birth control pills for a total of three or more years had more than double the risk for glaucoma compared with women who never used the Pill or who had stayed on it for less than three years. The increased risk was found with three or more years of cumulative use of the Pill, not just with continuous use.

There are still a lot of unanswered questions. For instance, the study did not look at whether the glaucoma risk associated with oral contraceptive use topped out at three years or whether women who used the Pill longer—say, for a total of five or 10 or 20 years—might be at even higher risk than those who used it for three years. Nor did the study analyze which type or which dose of birth control pills the women used—and given that birth control pills used to contain much higher doses of hormones than they do now, accounting for these variables might significantly affect the findings.

Former pill users, take note: This study does not prove that birth control pills cause glaucoma…and given the unanswered questions, more research clearly is needed. Still, the findings are disquieting enough that women with a history of using oral contraceptives for a total of three years or longer would be wise to mention this fact to their ophthalmologists and discuss whether they might need any extra glaucoma screening during their annual eye exams. This is particularly important for women who also have other glaucoma risk factors, such as African heritage, diabetes, heart disease, high blood pressure, hypothyroidism or retinal problems…a history of smoking, early menopause (prior to age 45) or long-term use of corticosteroids…a family history of glaucoma…and those who are age 60 or older.

Good news: If glaucoma is detected in time, treatment can reduce eye pressure before the optic nerve suffers permanent damage…safeguarding the precious ability to see. For more ways to protect your vision, see our Guide to Eye Health—How to Save Your Eyes.