Ask the Doctors: Basal tears are crucial to eye health

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Q: I've got a blocked tear duct that I'm told requires surgery. My eye weeps, but it isn't painful. However, it has become infected once. What can you tell me about this condition, and what are my treatment options?

A: We're all aware of the tears we produce in abundance — such as when we cry in times of emotion, or when our eyes fill with reflex tears in response to an irritant. However, our eyes are continuously producing a third type of tear, known as basal tears.

As with most tears, basal tears come from the lacrimal glands, which are located above the outer third of each eye. Although basal tears aren't nearly as abundant as emotional or reflex tears — we secrete less than a gram of them per day — they are essential to the health and optimal functioning of the eye. With each blink, the eyelid spreads the basal tears, which coat the eye with a complex film of water mixed with mucus, fatty oils and more than a thousand different proteins. Basal tears lubricate and nourish the surface of the eye, most specifically the cornea. This is the clear, colorless dome that covers the front of the eye and forms its outermost layer. Basal tears also play an important role in focusing light.

After basal tears complete their journey down and across the eye, they drain into structures known as puncta. These are tiny openings in the corners of the upper and lower eyelid. The spent basal tears, along with whatever debris they may have cleared from the surface of the eye, then move through a series of ducts and canals that empty into the nose.

When any part of the tear drainage system becomes blocked, the constant flow of basal tears has nowhere to go. This causes them to back up onto the surface of the eye, which becomes watery, red and irritated. Other symptoms of a blocked tear duct can include swelling in the inner corner of the eyelid, blurred vision, mucous discharge and crusty lids or eyelashes. As you have already experienced, a blocked tear duct can also increase the risk of infection.

Blocked tear ducts in adults are most commonly caused by eye infections, swelling, injury to the nose or eye, polyps or a tumor. Age-related changes to the structures of the eye, such as narrowing of the punctal openings, can also play a role. Diagnosis entails a complete eye exam, as well as specific tests to assess the degree of blockage.

Treatment is based on the results of those tests. Infection is typically treated with a course of antibiotics. The blockage itself may respond to a special massage technique, or may require one of several different types of surgical intervention. These can include the use of a series of instruments to clear the blockage, opening a narrowed duct with a balloon catheter, implanting a temporary stent into the duct, or creating a new route for tears to drain from the eyes and through the nose.

As with any medical procedure, be sure to understand all of the available treatment options, and discuss them with your doctor.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.

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