Toward a Cure for Dry Eye
Dry eye syndrome, a condition that is especially prevalent in women as they age, happens when the quantity of tears is no longer sufficient to lubricate the eyes. A burning sensation is typical and impaired vision including damage to the cornea may result. In search of a cure, researchers led by Kara Maki Ph.D. at the Rochester Institute of Technology’s School of Mathematical Sciences in New York are testing computer simulations that map the way tears move across the surface of the eye. The study was published on May 6th 2014 in the journal Physics of Fluids.
A release from the university written by Susan Gawlowicz quotes Dr. Maki as saying, “We’re hoping if we can understand better the basic dynamics of the tear film, then we can start to understand what goes wrong if you have dry eye and start to think about potential cures by studying simulations.”
The release notes that dry eye is a common condition without a cure. Many causes, including the aging process, contribute to discomfort resulting from either a lack of tears or tears that evaporate too quickly. In the United States alone, nearly 5 million people age 50 and older suffer from dry eye, according to the National Eye Institute, part of the National Institutes of Health. Women are predominantly afflicted with the condition, with more than 3 million diagnosed with dry eye due to hormonal changes associated with menopause. Treatment to alleviate symptoms includes eye drops and temporary or surgical plugs to stopper tear ducts at the inner corners of the eyes and retain fluid.
“One thing we were able to find is that when your eyes are open, the tears get thin right along the edge of the eye, and that is referred to as the ‘black line,’” Maki said. “That has been seen clinically and can be reproduced in our simulations.”
The tears, Maki explains, climb up the eyelid and join a column of fluid that travels along the lids. Lower pressure sucks the fluid into the meniscus and away from the center, creating the black line and dry spots in the tear film that can compromise vision and irritate the cornea.
Maki saturated the eye with liquid to penetrate the black line. She wanted to know if the fluid would travel down the front of the eye and relieve the thinning of the tear film.
“We found that we had to really flood the eye in our simulations. The fluid would rather travel in the meniscus,” Maki said. “It splits traveling along the upper lid and the lower lid. We confirmed that blinking is necessary to stop this thinning from happening. Every time you blink, the tear film gets repainted on the front of your eye. It’s important to have smooth tear film for optical quality.”
The next step for Maki and colleagues is to simulate the dynamics of tear films in a blinking eye.
“The nice thing about having a model is that you can make unrealistic things happen,” Maki said. “For example, we can flood the eye and see where the tears go. Or we can look at what happens when the drainage holes are plugged. Where does the fluid go? You can start to explore these things in a safe way.”
In addition to Maki and Braun, the dry-eye team includes Longfei Li, William Henshaw and P.E. King-Smith.