University of Tokyo researchers have shown for the first time that caffeine intake can significantly increase the eye’s ability to produce tears.
This finding could improve the treatment of dry eye syndrome.
Dry eye syndrome is a common eye condition that affects about four million people age 50 and older in the United States.
For many, dry eye syndrome is simply uncomfortable, but for others it escalates into a vision-threatening disease. All of the 78 participants in the new study produced significantly more tears after consuming caffeine than after taking a placebo. The study appears in the journal Ophthalmology.
Dry eye syndrome involves malfunction of the rate of tear production, the quality of tears, and/or the rate of evaporate from the surface of the eye. Anyone can experience dry eye, though it is more common among women. Symptoms can include gritty, scratchy or burning sensations, excessive tearing, and/or production of stringy mucus.
Led by Reiko Arita, MD, PhD, the research team was motivated by an earlier study that had shown a reduced risk for dry eye in caffeine users: 13 percent of users had the syndrome compared with nearly 17 percent of non-users.
The team knew that caffeine was likely to stimulate tear glands, since it is known to increase other secretions, such as saliva and digestive juices.
They also knew that people respond differently to caffeine, so they analyzed study participants’ DNA samples for two genetic variations that play important roles in caffeine metabolism. Tear production proved to be higher in study subjects who had the two genetic variations.
“If confirmed by other studies, our findings on caffeine should be useful in treating dry eye syndrome,” said Dr. Arita.
Dry eye can be very uncomfortable and interfere with vision. It’s important to see an ophthalmologist if symptoms continue, since advanced cases can cause eye damage and permanent vision problems.
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Ophthalmology. the journal of the American Academy of Ophthalmology, 2012 Feb 14., Epub ahead of print, “Caffeine Increases Tear Volume Depending on Polymorphisms within the Adenosine A2a Receptor Gene and Cytochrome P450 1A2.”Arita R, Yanagi Y, Honda N, Maeda S, Maeda K, Kuchiba A, Yamaguchi T, Yanagihara Y, Suzuki H, Amano S. Itoh Clinic, Saitama, Japan; Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan.
Schaumberg DA, Sullivan DA, Buring JE, Dana MR. “Prevalence of dry eye syndrome among US women.” Am J Ophthalmol. 2003;136:318-26.
Schaumberg DA, Dana R, Buring JE, Sullivan DA. “Prevalence of dry eye disease among US men: estimates from the Physicians’ Health Studies.” Arch Ophthalmol. 2009;127:763-8