Could Caffeine Help Dry Eye?
Scientists Find Caffeine May Boost Tear Production
Caffeine for Dry Eye: Study Details continued...
Arita also knew caffeine was likely to stimulate tear glands, since it also increases saliva, digestive juices, and other secretions.
It's also known that people differ in their response to caffeine, depending on their DNA. Arita's team analyzed the DNA of everyone in the study. They looked at two genetic variations that affect caffeine metabolism.
None of the men or women had dry eye, eye allergies, or other problems. They participated in two sessions, separated by six days or less. In one, they took either a caffeine capsule or a placebo, which looked the same.
The amount of caffeine given depended on a person's weight; those who weighed 127 to 165 pounds, for instance, got a 400 milligram caffeine capsule. One 8-ounce cup of brewed coffee contains about 100 milligrams of caffeine.
During the second session, they were given the other capsule.
Arita's team measured the total volume of tears. Everyone had more tears after taking the caffeine capsule than the placebo. Some participants reported caffeine side effects such as increased heart rate, sweating, trembling, palpitations, and wakefulness.
Those who had the genetic variations had higher tear production than those who didn't.
Arita can't explain yet exactly why caffeine appears to boost tear volume.
Caffeine for Dry Eye: Perspective
The idea could have merit but needs much more research, says Pedram Hamrah, MD, attending physician and surgeon at Massachusetts Eye and Ear and assistant professor of ophthalmology at Harvard Medical School.
He reviewed the findings but did not take part in the study.
"All they are showing is in a normal person who doesn't have dry eye, if you give them caffeine they have some increase in tear production right after," he says. It's not certain if the effect lasts, Hamrah says.
Most who have dry eye also have a high rate of tear evaporation, he says. The caffeine research doesn't address that.
Hamrah reports serving as a consultant for ReVision Optics, Allergan, Alcon, and Fovea Pharmaceuticals.
"It is logical that caffeine might stimulate tear production in many individuals," says Marguerite McDonald, MD, an ophthalmologist in Lynbrook, N.Y., and a clinical professor of ophthalmology at NYU Langone Medical Center. She also reviewed the findings.