Treating yourself to three cups of coffee a day could increase your risk of vision loss and blindness, according to US research.
Regular coffee consumption specifically increases our likelihood of developing psuedoexfoliation glaucoma, a type of glaucoma that effects between 25 and 30 percent of glaucoma patients.
Glaucoma is usually caused by a blockage of the circulation or drainage of the fluid that circulates in the eye, which causes pressure to build in the eyeball and damages the optic nerve. In psuedoexfoliation glaucoma, material rubs into the iris and lens, which clogs the eye's drainage system.
Researchers from the Brigham and Women's Hospital in Boston believe compounds found in coffee could increase pressure in the eyeball to cause psuedoexfoliation glaucoma.
The study surveyed 120,000 people aged over 40 from the UK and US about how much coffee they drank. None of their medical records showed a history of glaucoma.
The researchers found people who drank more than three cups of coffee a day had a greater risk of developing psuedoexfoliation glaucoma. However other caffeinated products, such as tea and chocolate (which has small amounts), did not appear to have an impact.
Professor Jonathan Crowston, managing director of the Centre for Eye Research Australia, told ninemsn the risk was only slight, so there is no need for coffee lovers to abstain altogether.
"It's a fairly weak association and only pertains to a small subset of glaucoma," he said.
"As with all things in life, in moderation it is probably safe."
The best way to prevent glaucoma causing blindness is to get regularly checked if you are at risk.
"The key message would be that if you have a family history of glaucoma or a known risk factor for glaucoma, such as high eye pressure, you get your eyes examined on a yearly or every other year basis," Professor Crowston said.
"The strongest risk factor for going blind from glaucoma is getting it picked up late."
Glaucoma is the leading cause of irreversible blindness in the world. One in 10 Australians over the age of 80 will develop glaucoma.
The study was published in the journal Investigative Ophthalmology & Visual Science.