Dry eye syndrome is not fatal and only rarely leads to blindness.
But for people with the problem, dry eyes can be anything from annoying to life-wrecking. Their eyes feel gritty, scratchy, parched, as if they are being slowly sanded away. Perhaps because eyes have so many more nerves than other parts of the body, they can hurt so much that all a sufferer wants to do is to crawl off in a corner and close them. Sunlight can make things even worse. So can wind.
Dry eye syndrome "is often pooh-poohed because it doesn't usually cause blindness," says Dr. Janine Smith, deputy clinical director of the National Eye Institute in Bethesda, Md. But it can destroy quality of life. "You have to blink all the time. You can't keep your eyes open. If you have a job, it's hard to do it."
An estimated 4 million Americans, most of them women, have moderate to severe forms of the condition; 6 million more have milder forms.
"Dry eye doesn't kill anybody, but it can drive some people to want to kill themselves," says Dr. Anthony Aldave, director of cornea and refractive surgery at the Jules Stein Eye Institute at UCLA. It also can make wearing contact lenses impossible.
Psychologist Teri Rumpf, 55, of Newton, Mass., says sometimes her eyes become so dry that "you can't open your eye because the lid sticks to the cornea," she says. "You kind of pry it open."
More than just water
Scientists now have a much better handle on the causes of dry eye. And new drugs to treat the condition are either already approved by the Food and Drug Administration or are in the process, a potential boon not just to sufferers but to contact lens manufacturers who want to maintain their large market.
Dry eye is a condition in which there is a reduction in the quality or quantity of tears, says Debra Schaumberg, director of ophthalmic epidemiology in the division of preventive medicine at Brigham and Women's Hospital and an assistant clinical scientist at the Schepens Eye Research Institute, both in Boston: "The function of tears is to lubricate the ocular surface and keep it healthy," she says.
Tears are not just water but a complex fluid consisting of three layers. The bottom layer, closest to the eyeball, is called mucin, which is made in three types of cells on the surface of the eyeball. The watery middle layer is made in the lacrimal glands, which lie under the eyebrow. And the outermost layer, composed of lipids, is made in the meibomian glands behind the upper and lower eyelashes.
The two most common forms of dry eye are the "aqueous deficient" type, in which there's not enough production of the watery layer, and the "evaporative" type, in which there's not enough of the lipid (outer) layer to keep tears from evaporating.
Leading causes of the aqueous form are autoimmune diseases such as lupus, rheumatoid arthritis or Sjogren's syndrome, says David Sullivan, a senior scientist at Schepens. One reason women get almost three times the dry eye problems as men is that women are more prone to autoimmune disease.
In Sjogren's syndrome, for instance, which includes dry mouth as well as dry eyes, immune cells mistakenly attack the lacrimal and salivary glands, says Dr. Douglas Jabs, a professor of ophthalmology and medicine at Johns Hopkins University School of Medicine. This autoimmune disorder eventually leads to destruction of the lacrimal glands and thus decreased production of the watery portion of tears.
But other factors are at play as well, says Sullivan, most notably the hormone androgen, which is present in both men and women but at higher levels in men. Both the lipid-making meibomian glands and the water-making lacrimal glands respond to androgens. With aging, both sexes make less androgen, but this is particularly pronounced in women because they have less androgen to start with.
Androgen has another role as well, damping down the immune system, including the inflammatory response. Women who are androgen-deficient thus face a double whammy: They don't have enough androgen to make tears, and they don't have androgen's soothing effect on inflammation in the lacrimal glands.
"Curiously, estrogen replacement therapy does not help," says cell biologist Ilene Gipson, director of the Women's Eye Health Task Force at Schepens. In fact, it makes things worse, says Schaumberg of Brigham and Women's.
Her research shows that women taking hormone replacement therapy have an increased risk of dry eye, perhaps because estrogen may decrease the function of the meibomian glands.
Taking steps toward relief
In addition to over-the-counter "artificial tears" that provide temporary relief, other treatments that can ease dry eye symptoms include taking supplements of omega-3 fatty acids or eating fish rich in omega-3s, such as tuna.
In a procedure called punctal occlusion, a doctor inserts silicone plugs into the ducts near the corner of the eye by the nose to keep tears from escaping. Some people have their ducts cauterized (surgically scarred) for more permanent relief. Others turn to thick, swimming-type goggles that enclose the eyes to keep air out. In rare cases, people have their eyelids sewn partly shut to keep moisture in.
But the most exciting advances are in new prescription drugs. Restasis, already on the market, reduces inflammation on the eye surface. Another drug, not yet approved, is diquafosol, designed to increase fluid volume on the surface of the eyeball. Anti-inflammatory drugs for dry eye are in the works.
Finally, studies are underway on topical androgen eye drops made by Allergan Inc. of Irvine, designed to combat the androgen deficiency of many cases of dry eye.