- A 120,000-person study has tied drinking three cups per day to developing exfoliation glaucoma.
- About 2.2 million Americans age 40 and older have glaucoma, the second-most common cause of blindness worldwide after cataracts. Glaucoma is the name for a group of diseases in which fluid builds up inside one or both eyes, increasing the internal pressure and eventually damaging the optic nerve. If left untreated, people with glaucoma slowly lose their peripheral vision. Over time, central vision can also deteriorate.
This is what ophthalmologists see when they look in your eyes. The bright little circular part in the center is the optic nerve. They look for changes in its shape when diagnosing glaucoma
PROBLEM: A group at Harvard School of Public Health -- who'd previously conducted a smaller study that associated caffeine with a somewhat increased risk of primary glaucoma -- noted that people in Scandinavian countries have the highest rates of exfoliation glaucoma (EG) in the world, and that they also consume the most coffee. In an ongoing search for causes of EG, they suspected the two might be related. That was corroborated by knowledge that caffeine affects levels of homocysteine in our eyes, and that homocysteine levels are often high in people with EG.
A little on EG: The study's authors note it's "the leading cause of secondary open-angle glaucoma worldwide." It accounts for 7-12 percent of glaucoma. As we understand it, EG is due to pigments in your eye coming loose and blocking the flow of liquid out of your eyeball, which leads to increased pressure, changes in the optic nerve, and/or vision problems. A diagnosis of EG doesn't mean vision loss, though.
Lots of research on the causes of EG is happening. The stated purpose of this study was to look at risk factors for developing it.
They didn't report on an association with actual vision loss.
The trend "did not robustly extend to caffeinated product consumption generally."
CONCLUSION: Drinking a lot of coffee is associated with increased risk of developing exfoliation glaucoma, and thereby a risk of impaired vision and blindness.
IMPLICATION: This is a large, prospective study worth factoring into the increasingly expansive discussion on coffee's plusses and minuses. "Life without life's joys is living death." And then, buried in the paper was this little gem: "The highest caffeine consumers were somewhat less likely to have hypertension, diabetes, high cholesterol, and myocardial infarction."
Takeaway, get screened for glaucoma regularly, even if you've never had any coffee ever. There were 44.8 million people with open-angle glaucoma in the world in 2010, and by 2020 there will be 58.6 million. We can't jump to saying this glaucoma-coffee association is definitely causal and that no one should drink coffee. I'm actually drinking some very bad coffee right now. If, for the time, though, these findings promote glaucoma awareness and continued research on the tremendous amounts of coffee and caffeine we drink/eat/rub all over our bodies, it's useful and good.