WATERY EYES

The eyelids play a key role in protecting the eyes. They help spread moisture (tears) over the surface of the eyes when they close (for example, while blinking); thus, they help prevent the eyes from becoming dry. The eyelids also provide a mechanical barrier against injury, closing reflexively when an object comes too close to the eye. The reflex is triggered by the sight of an approaching object, the touch of an object on the surface of the eye, or the eyelashes being exposed to wind or small particles such as dust or sand.

Tears are a salty fluid that continuously bathes the surface of the eye to keep it moist. This fluid also contains antibodies that help protect the eye from infection. Tears are produced by the lacrimal (tear) glands, located near the outer corner of the eye. The fluid flows over the eye and exits through two small openings in the eyelids (lacrimal ducts); these openings lead to the nasolacrimal duct, a channel that empties into the nose.

If the lacrimal glands don't produce enough tears, the eyes can become painfully dry and can be damaged. A rare cause of inadequate tear production is Sjögren's syndrome. (see page 234 in Chapter 51, Disorders of Joints and Connective Tissue) The eyes can also become dry when evaporation causes an excessive loss of tears, for example, if the eyelids don't close properly.

NASOLACRIMAL DUCT BLOCKAGE

Blockage of the nasolacrimal duct (dacryostenosis) can result from inadequate development of the nasolacrimal system at birth, a chronic nasal infection, severe or recurring eye infections, or fractures of the nasal or facial bones. Blockage can be partial or complete.

Blockage caused by an immature nasolacrimal system usually results in an overflow of tears that runs down the cheek (epiphora) from one eye or, rarely, from both eyes in 3- to 12-week-old infants. This type of blockage usually disappears without treatment by the age of 6 months, as the nasolacrimal system develops. Sometimes the blockage resolves faster when parents are taught to milk the duct by gently massaging the area above it with a fingertip.

Regardless of the cause of the blockage, if inflammation of the conjunctiva (conjunctivitis) develops, antibiotic eyedrops may be needed. If the blockage doesn't clear up, an ear, nose, and throat specialist (otorhinolaryngologist) or an eye specialist (ophthalmologist) may have to open the duct with a small probe, usually inserted through the duct opening at the corner of the eyelid. Children are given general anesthesia for this procedure, but adults need only local anesthesia. If the duct is completely blocked, more extensive surgery may be needed.

LACRIMAL SAC INFECTION

Usually, infection of the lacrimal sac (dacryocystitis) results from a blockage of the nasolacrimal duct. The infection makes the area around the sac painful, red, and swollen. The eye becomes red and watery and oozes pus. Slight pressure applied to the sac may push pus through the opening at the inner corner of the eye, near the nose. The person also has a fever.

If a mild or recurring infection continues for a long time, most of the symptoms may disappear, with only slight swelling of the area remaining. Sometimes, an infection causes fluid to be retained in the lacrimal sac, and a large fluid-filled sac (mucocele) forms under the skin. Recurring infections may produce a thickened, red area over the sac. An abscess may form and rupture through the skin, creating a passage for drainage.

The infection is treated with oral or intravenous antibiotics. Applying frequent warm compresses to the area also helps. If an abscess develops, surgery is performed to open and drain it. For chronic infections, the blocked nasolacrimal duct may be opened with a probe or by surgery. In rare instances, surgical removal of the entire lacrimal sac may be necessary.

(Extracts in this section compiled from: The Merck Manual of Medical Information.)