Dry eye is a potentially debilitating condition that affects millions of Americans. It can cause burning, scratching or stinging sensations in the eye due to lack of tears, which are needed to lubricate your eyes and wash away particles and foreign bodies.
In addition to burning or stinging sensations, dry eye may also cause you to have strained or tired eyes after even short periods of reading. Prolonged bouts of dry eye can eventually lead to tiny abrasions on the eye surface.
“For many years, dry eye has been neglected by ophthalmologists,” says Samuel Yiu, M.D., Ph.D., assistant professor of ophthalmology at the Keck School of Medicine of USC. “Only recently have we made strides in research for treatment of dry eye. It is still mostly a management issue as no cure exists, but I am hopeful for the future.”
Traditional treatments for dry eye include using artificial tears in the form of drops or ointment, or simply prevention by avoiding triggers such as smoke and dry air. Restasis®, approved by the Food and Drug Administration in 2002, is the only prescription eye drop available to help increase tear production.
According to Yiu, part of the problem in treating dry eyes is that the cause is not always easy to pinpoint. Dry eye can be caused by a variety of factors including aging, sun exposure, smoking, eye injuries and Sjögren’s syndrome, an autoimmune disease in which the body mistakenly attacks its own moisture producing glands. Dry eye is a hallmark symptom of Sjögren’s syndrome, which typically strikes women over age 40. Therefore, before treatment can be advised, a lengthy evaluation of both the physical and environmental history of the patient must be taken.
“A lot of women with dry eye have underlying autoimmune problems,” says Yiu, also a researcher at the Doheny Ocular Surface Center of USC’s Doheny Eye Institute. “This is something that needs to be addressed when dealing with dry eye.”
To that end, Yiu often implements a multi-team approach when working with women in his dry eye clinic, including gynecologists and rheumatologists.
In addition to a lack of information on the cause of dry eye, little is known about how the lacrimal gland—the part of the eye responsible for producing tears—actually works or why it stops working in patients with dry eye. However, scientists at the Doheny Eye Institute are providing a greater understanding of the inner workings of the tear producing glands and moving towards innovative treatments for dry eye.
Studies from Doheny researchers support an idea that the cells in the lacrimal gland, along with the cells that cover the surface of the eye, function as part of what scientists call the “mucosal immune system.” This immune system protects and defends moist fragile tissues—such as the linings of the respiratory, gastrointestinal, urinary and reproductive tracts, and the surface of the eye—from the external environment.
So while tears play an important role in keeping the eyes moist and comfortable, they also contain beneficial antibodies that immobilize germs and prevent them from invading the cornea or sclera (the whites of the eyes).
Knowing this, researchers have begun to study ways to trigger “normal” functioning of the immune response that causes tears. This means they may be able to treat dry eye from the inside out.
In addition, some researchers believe that the onset of dry eye may have something to do with hormones, especially in women. Yiu and his group recently analyzed a small number of female patients with dry eye who used an established hormone-replacement therapy. The results seem to explain why many more women than men experience dry eyes, particularly after events such as pregnancy when hormones fluctuate dramatically.
Yiu and his group have also made significant advancements toward development of a bioengineered artificial lacrimal gland, designed to be implanted above the eye and beneath the skin to produce tears. The device is geared towards people who have severe cases of dry eye as a result of advanced eye disease or facial burns or trauma.
“I believe that the lacrimal (tear producing) glands aren’t dead, they are just non-active,” says Yiu. “If we can find a way to wake them, I think the patient will produce healthy tears again.”