Coffee is thought to increase intraocular pressure (IOP) in patients with open angle glaucoma (OAG) and ocular hypertension. The likely culprit: caffeine, right?

Whoa, Joe. Not so fast.

Researchers in Maryland and India tested the pressure-raising effect of caffeine by applying it several times a day directly to the eyes of five patients with OAG and ocular hypertension.

Their conclusion: Caffeine did not have any effect on IOP. “Any effects reported in coffee drinkers may therefore be related to other constituents in coffee ... combined with the osmotic effects imposed by adequate fluid intake, known to be common in glaucoma patients,” the researchers wrote in November’s Clinical Ophthalmology.