The human eye constantly produces tears to keep its surface clean, moist, and protected. This fluid is generated by the lacrimal glands and spreads across the eye with every blink. A precise drainage system, known as the lacrimal apparatus, collects and channels this fluid away to prevent a constant stream of tears down the face. A blocked tear duct, medically termed nasolacrimal duct obstruction, occurs when this drainage pathway becomes partially or completely obstructed. When blocked, tears cannot flow into the nasal cavity, causing them to back up and spill over the eyelid margin.
The Primary Visible Sign
The most noticeable sign of a blocked tear duct in an adult is continuous, excessive watering of the eye, a condition known as epiphora. This is characterized by clear, watery tears that perpetually sit on the lower eyelid, often overflowing and running down the cheek even when the person is not crying. The overflow results directly from tears having nowhere else to go once the capacity of the tear drainage system is exceeded.
The constant presence of tears on the skin can lead to chronic wetness, irritation, and sometimes minor chafing of the surrounding periorbital skin. The persistent moisture is generally localized to one eye, as blockages in adults are typically unilateral. This excessive tearing often becomes worse when exposed to environmental factors like cold air, wind, or bright sunlight. Additionally, simple actions like bending over can exacerbate the visible tearing, as the change in head position forces the stagnant fluid to spill out.
The pooling of tears on the eye surface can cause the vision to appear mildly blurred or smeared, a temporary effect of the excessive moisture. Unlike tear production caused by irritation, which often stops once the irritant is removed, the tearing from a blocked duct is constant because the underlying drainage problem remains. The tears themselves look normal, but their unremitting presence serves as the primary visible clue to the obstruction.
Associated Physical Changes and Complications
While simple overflow is the initial presentation, a blocked tear duct can progress to more serious physical changes if the stagnant tears become infected, a condition called dacryocystitis. This complication presents as a distinct, painful swelling located precisely at the inner corner of the eye, adjacent to the nose. The skin over this area, which corresponds to the lacrimal sac, will appear visibly red and tender.
The redness and swelling are highly localized, differentiating them from generalized eye inflammation, and may be accompanied by warmth. As the infection progresses, a visible discharge may be present, which can be thin mucus or thicker, yellowish-green pus. This material may spontaneously seep from the tiny openings on the eyelid margin (the puncta), or it may crust and mat the eyelashes together, especially upon waking.
In a chronic, low-grade infection, the swelling may be less pronounced, but the eye will still show persistent mucoid discharge and tearing. The presence of this discharge, often accompanied by crusting, signals that the blocked sac has become a breeding ground for bacteria. The visual appearance of a tense, inflamed lump at the medial canthus strongly indicates an active infection requiring immediate medical attention.
Distinguishing a Blocked Duct from Other Eye Conditions
When attempting to identify a blocked tear duct, it is useful to compare its appearance to other common conditions that cause watery or red eyes. Unlike allergic conjunctivitis, a blocked duct usually affects only one eye and does not cause the intense, generalized itching that characterizes an allergic reaction. Allergic responses tend to cause a diffuse, bilateral redness across the white of the eye and are often seasonal.
Pink eye, or infectious conjunctivitis, involves widespread redness across the entire conjunctiva, giving the eye a distinctly bloodshot look. While a blocked duct can cause some redness, it is often minimal or strictly localized to the inner corner near the swelling. Furthermore, the discharge from bacterial conjunctivitis is often copious and purulent, whereas a simple blockage primarily causes tear overflow until an infection sets in.
Paradoxically, severe dry eye syndrome can cause reflexive tearing as the eye attempts to compensate for surface dryness. However, dry eye is marked by a chronically irritated, bloodshot surface and a gritty sensation, without the specific, localized swelling at the inner corner seen with a blocked duct infection. The defining visual feature of the blocked tear duct remains the continuous overflow of tears combined with the potential for focal swelling at the nose-side of the eye.