Q: As I have gotten older, I notice that my eyes are almost constantly dry. I use over-the-counter eye drops, but I also have itching and redness. What causes dry eyes?

A: Dry eye disease is a common condition that can cause uncomfortable side effects. Symptoms often include blurry vision; eye redness; sensitivity to light; and a burning, gritty or scratchy feeling in your eyes. Dry eyes occur because the eyes do not produce enough tears or the tears are not adequate to keep the eyes properly lubricated.

To keep your vision clear and your eyes comfortable, you need a smooth layer of tears consistently covering the surface of your eyes. The tear film has three components: oil, water and mucus. Problems with any of these can cause dry eyes.

Many people may experience dry eyes during their lifetime. Aging, environment, hormones, air travel, the outdoors — many factors contribute to the lubrication of the eye. Medications, age, eyelid problems and excessive eye strain all can result in dry eyes. Certain medical conditions also may increase risk for dry eyes, including rheumatoid arthritis, lupus, scleroderma, sarcoidosis and thyroid disorders.

Dry eyes can affect vision. It is important to be evaluated, especially if you have redness, itching or pain.

For some people with chronic dry eyes, the problem stems from glands in the eyelids, called the meibomian glands. Normally, these glands make oil that slows the evaporation of tears. If the glands become blocked, tears do not contain enough oil. The tears evaporate too quickly, and eyes become dry. This type of dry eye condition is known as evaporative dry eye. Inflammation of the eyelid skin — a disorder called ocular rosacea — often can result in blocked meibomian glands.

The first line of treatment is over-the-counter lubricating eye drops. Many brands contain preservatives that help minimize the risk of infection. But over time, the preservative can become toxic to the surface of the eye. For chronic dry eye sufferers — those who use lubricating eye drops more than four times a day — preservative- free eye drops are best. Consider single-use vials since they can be discarded after use, minimizing the risk of contamination. Do not touch the eye when using drops, as it could lead to infection.

If you have symptoms of dry eyes that do not respond to drops or other standard therapies, speak to an eye specialist, as other treatments could help if the problem is blocked tear ducts, including anti-inflammatory medications, neurostimulators that can trigger or increase tear production, and steroids to reduce inflammatory conditions.

If you have dry eyes, pay attention to these situations that are most likely to increase your symptoms.

Consider wraparound sunglasses: Safety shields can be added to the tops and sides of eyeglasses to block wind and dry air.

Take breaks during long tasks: If you’re reading or doing other tasks that require visual concentration, take periodic eye breaks. Close your eyes for a few minutes. Or repeatedly blink for a few seconds to spread your tears evenly over your eyes.

Check the environment: The air at high altitudes, in desert areas and in airplanes can be arid. When in these spaces, frequently close your eyes for a few minutes to minimize tears’ evaporation.

Position your computer screen below eye level: If your computer screen is above eye level, you’ll open your eyes wider to view the screen. Position the screen below eye level so that you won’t open your eyes as wide. This may help slow the evaporation of your tears.

— Dave Patel, M.D., Ophthalmology, Mayo Clinic, Scottsdale, Arizona

Mayo Clinic Q&A is an educational resource and doesn’t replace regular medical care. Email a question to MayoClinicQ&A@mayo.edu.