Overview of Tear Duct Obstruction
Dacryostenosis, also known as a blocked tear duct, is a fairly common condition that disrupts normal tear drainage. It occurs in infants, in older children, and adults. It is generally not a serious condition and rarely poses a threat to vision.
The outer layer of the eye is coated by a three-layered tear film. The tear film serves several purposes:
- Keeps the eyes moist
- Protects the eyes from infection and irritation
- Keeps the surface of the eyes smooth so light can pass through easily
The outermost surface of the tear film is oil produced by the meibomian gland. Its purpose is to keep the tear surface smooth and reduce evaporation of the watery layer beneath it. Tears (water, aqueous portion), which make up the middle layer, are produced by the lacrimal cells. Their job is to cleanse the eye and wash away foreign materials and irritants. The third layer is mucus produced by conjunctival goblet cells. Mucus helps keep the eye moist by allowing the tears to spread evenly over the eye.
Tears from the surface of the eye normally drain into the nose through a tube called the nasolacrimal duct. If this duct is obstructed or blocked, the tears are unable to properly drain and overflow onto the cheek. Blockage can be caused by different factors. In infants, the duct may be incompletely developed. In most cases, blocked tear ducts in babies resolve on their own, usually before the first birthday. Tears are essential to eye health and function; when disruption in their production or drainage is caused by a blockage, treatment is needed to open the obstruction. In adults and older children, obstruction may be due to infection, injury, or a tumor.
Incidence and Prevalence of Tear Duct Obstruction
About 500,000 people in the United States are affected by dacryostenosis every year. Most cases are children under the age of 2 and adults over the age of 50. About 6% of babies are born with a blocked tear duct (usually in one eye only). The condition resolves with little or no treatment by the infant's first birthday in more than 90% of cases.
Causes for Tear Duct Obstruction
Although dacryostenosis can occur at any age, it is most common in infants who have an inborn obstruction of the nasolacrimal duct. The valve of Hasner, which is located at the end of the duct, is the most common place for blockage to occur. Either the membrane covering the valve in utero did not dissolve, or the drainage channel is narrower than normal.
In adults, blockage can be caused by the following:
- Enlargement of facial bones near the nose, due to aging
- Idiopathic inflammation (i.e., inflammation with an unknown cause)
- Infection in the tear duct
- Nasal polyps
- Sinus disease
- Trauma to the eye or nose
Dacryocystitis is an infection of the tear sac that may result from a blocked duct. Because the tears do not drain normally, bacteria can collect in the ducts or the tear sac. Dacryocystitis can develop into a chronic condition and can spread to adjacent sinuses and into the bloodstream, if the infection is not treated effectively.
Signs and Symptoms of Tear Duct Obstruction
The primary symptom of a blocked tear duct is excessive tearing. The tears may overflow onto the face and run down the cheek. There is often a mucous discharge as well. This condition may occur in both eyes.
Infection is common and may even be the reason for the blockage. Symptoms of infection include redness or swelling of the inner corner of the lower lid, discharge, and tenderness.