It’s easy to imagine that dry eyes have a simple cause, like allergies, dry air, or worn-out contact lenses. And sometimes that's true. But if your eyes feel dry, irritated, or sore for a long time, there might be more going on.
There’s a complicated link between your body’s immune system and your eyes. Inflammation, your body’s response to wounds and germs, can contribute to dry eyes. In turn, dry eyes can make eye inflammation worse.
That’s why doctors sometimes say dry eye disease is a “vicious cycle of inflammation.”
What Is Inflammation?
When cells in your body are damaged -- by a wound, bacteria, or a toxic chemical -- your immune system sends lots of white blood cells to the injured area. These cells launch an inflammatory response to repair the damaged tissue.
During this process, blood vessels leak fluid into the area. This can make it red, hot, swollen, and sore. And cells there might not work the right way while the inflammation is going on.
What's the Link Between Inflammation and Dry Eye?
When there’s inflammation in your tear glands, cornea, or conjunctiva (outermost layers of your eyes), your body may not make enough tears. Or your tears won't be made of the right mixture of water, oils, and salts. These changes make your eyes dry.
When your eyes aren't well-lubricated, they're not as good at washing away dirt, dust, and germs. This makes you more likely to get small cuts on the outer surface of your eye (called corneal abrasions) or infections.
Stress to your eyes, whether it’s an infection or a scratch on your cornea, then triggers your body to start an immune response there. This inflammation is your body’s attempt to heal your eye. But it can make dry eye worse.
Research has shown that over time, eye inflammation can lead not only to temporary changes in your tears, but long-term changes to nerves in your eyes. Long-term inflammation can also cause other cells in your eyes to die, leading to long-lasting eye conditions.
Treating the Inflammation
For years, the most common treatment for dry eye was artificial tears and other ointments that keep the surface of your eyes moist. These, and other remedies like avoiding smoke and wearing protective glasses, still work for some people with milder cases of dry eyes. Doctors can also prescribe tear-making drugs, eye inserts that lubricate your eyes, or special contacts to keep your eyes moist.
But with scientists' understanding of dry eye as an inflammatory disease, researchers have increasingly focused on drugs that target your immune system.
Many of the drugs your doctor might prescribe for dry eye work by blocking the immune activity that makes your eye inflamed. When the inflammation stops, normal tear production can begin again. Some of the anti-inflammatory drugs used to treat dry eye include: