The small opening near the inner corner of your eyelid is a normal and necessary part of your eye’s architecture. This tiny feature is integral to maintaining eye health by managing the constant flow of tears. It serves as the entry point to an elaborate plumbing system designed to drain excess fluid from the eye’s surface. Understanding this structure helps explain why your eyes stay clear and why they sometimes feel watery or irritated.
The Anatomy of the Lacrimal Punctum
This opening is scientifically known as the lacrimal punctum (puncta, plural). There are typically four puncta: one on the margin of the upper eyelid and one on the lower eyelid for each eye. They are strategically placed on a slight elevation called the lacrimal papilla, located near the inner corner closest to the nose (the medial canthus).
The punctum is a minute opening, often measuring between 0.2 and 0.3 millimeters in diameter. This small hole leads directly into a tiny tube called the canaliculus, a delicate passageway within the eyelid. The upper and lower canaliculi generally merge to form a common canal that then empties into the lacrimal sac.
The puncta are angled to dip into the tear meniscus, the pool of tears that collects along the lower eyelid margin. This precise positioning allows them to efficiently collect tear fluid from the eye’s surface. This structure is part of the larger lacrimal apparatus, which includes glands for tear production and drainage.
The Essential Function of Tear Drainage
The primary role of the lacrimal punctum is to act as the initial drainage port for the eye’s tear film. Tears are continuously produced by the lacrimal glands to lubricate, nourish, and protect the eye surface. The tear film, which includes water, oil, and mucus, spreads across the eye with every blink.
After the tears have cleansed the eye, they collect at the inner corner and are drawn into the puncta. Fluid movement through the canaliculi is driven by capillary action and the mechanical force of blinking. When the eyelids close, muscles surrounding the lacrimal sac contract, creating negative pressure that actively draws tears into the system.
The tears flow from the canaliculi into the lacrimal sac, a small reservoir nestled near the nose. From the sac, the fluid continues downward through the nasolacrimal duct (tear duct), which runs through the bone and ultimately empties into the nasal cavity. This explains why excessive tearing often causes a runny nose, as the fluid drains directly into the nasal passages. This system prevents tears from spilling over the eyelid margin, a condition known as epiphora.
When the Punctum Causes Problems
While the punctum is usually functional, its small size makes it vulnerable to issues that disrupt drainage. The most common problem is punctal stenosis, a narrowing or complete blockage of the opening. This condition prevents tears from draining efficiently, leading to persistent, watery eyes and tear overflow.
Blockages can be caused by chronic inflammation, such as long-term eye infections or blepharitis, or from side effects of certain topical eye medications. If the blockage occurs further down the drainage system, such as in the lacrimal sac, it can lead to an infection called dacryocystitis. Symptoms include redness, swelling, and tenderness near the inner corner of the eye.
Other issues involve the punctum’s position, such as when the eyelid turns outward (ectropion). This pulls the punctum away from the eye’s surface, preventing it from collecting tears. In rare cases, individuals may be born with an absent or malformed punctum. Persistent watering, a painful lump, or discharge near the inner corner of the eye indicates a potential problem. Consulting an eye care specialist is the next step to diagnose the issue and restore normal tear flow.