Stand at a mirror and pull your lower lid down slightly at the inner corner, near your nose. That faint pinprick opening on the lid margin is a punctum, and you have four of them, one on each lid.
They are the beginning of your eye's plumbing. Tears spread across the eye, do their work, and leave through these openings. When a punctum narrows or closes, tears back up and run down your face, and when your eyes are too dry, a doctor may deliberately block one to keep tears in.
For a structure smaller than a printed period, it causes a surprising amount of trouble.
What a punctum is and where to find it
Each punctum is a small round opening on the edge of the eyelid, positioned close to the nose rather than in the middle of the lid. Both the upper and lower lid have one, and they sit almost facing each other so that a closed eye brings them together.
The opening is not just a hole in skin. It sits on a slightly raised bump with a ring of tissue around it that helps hold it open, and it leads into a narrow channel called a canaliculus. Healthy puncta point slightly back toward the eye, which is what lets them pick up tears from the pool that collects at the inner corner.
How a tear leaves the eye
Tears are produced above and to the outside of the eye, get swept across the surface by blinking, and gather at the inner corner. From there the path is short.
- Into the upper and lower punctum
- Along the canaliculi, the two small channels behind them
- Into the lacrimal sac, a small reservoir beside the bridge of the nose
- Down the nasolacrimal duct and out into the nose
Blinking is what powers this. Each blink squeezes the sac and channels in a way that pulls tears in and pushes them along, so drainage is active rather than passive. It also explains a familiar thing: when you cry, your nose runs, because the overflow is landing exactly where the duct empties.
A small share of your tears simply evaporates. The rest goes down this route, all day, without you noticing.
When the drain narrows or closes
Punctal stenosis means the opening has become too narrow to carry tears at a normal rate. The classic complaint is watery eyes, sometimes with tears spilling over the lid and irritating the skin below, and blurring that clears when you blink or dab.
It is easy to misread. Watering eyes feel like a tear production problem, but they are often a drainage problem, and dry eye itself can trigger reflex watering that overwhelms a narrow drain. Sorting that out is exactly what an exam is for.
Common contributors include:
- Chronic lid margin inflammation. Long-running irritation and crusting around the lash line can scar the opening down.
- Age-related change. Tissues around the opening stiffen and narrow over time.
- Lid position problems. If the lid turns outward, the punctum no longer sits against the eye and cannot collect tears, even when it is open.
- Infection, injury, or surgery. Scarring anywhere along the path can obstruct it.
- Certain medications. Some systemic and topical drugs are associated with narrowing.
- Conditions present at birth. Rarely, a punctum is absent, sealed over, or duplicated.
A blockage further along the system, in the sac or duct, produces similar watering. Swelling, redness, or tenderness beside the nose along with discharge suggests the sac itself is infected, and that warrants prompt care rather than watchful waiting.
Punctal plugs, and why anyone would block a drain
In dry eye, the problem is often not too little drainage but too little tear volume or tears that evaporate too fast. Closing off some of the outflow keeps what you have on the surface longer.
That is what a punctal plug does. It is a tiny insert placed into the opening during an office visit, usually without more than a numbing drop. Some are made to dissolve over days or months, which makes them a useful trial. Others are designed to stay until removed.
Plugs are one option among several, not a first move for everyone, and they are sometimes considered after refractive surgery when dryness lingers. They can also work loose and fall out, cause awareness or irritation, or overcorrect into watery eyes. Whether they fit your situation is a judgment your eye doctor makes after examining your tear film and lids, and there is nothing to buy or attempt yourself.
What an eye doctor looks at
Evaluation is straightforward. Your doctor inspects the puncta and lid position under magnification, checks the lid margins for inflammation, and assesses your tear film. Drainage can be tested by placing a dye and watching how quickly it clears, or by gently irrigating the channel. Depending on findings, treatment might address lid inflammation, correct lid position, dilate a narrowed opening, or open the passage surgically.
Common questions
Why does one eye water all the time?
Often drainage rather than overproduction: a narrowed punctum, a lid sitting away from the eye, or a blockage further down. Chronic dryness can also cause reflex tearing, so a look is worth more than a guess.
Can I unclog a punctum myself?
No. It is delicate tissue, and probing it risks real damage. Warm compresses and lid hygiene may help the inflammation around it, but the opening itself is a job for a clinician.
Are punctal plugs permanent?
Not usually. Dissolvable types disappear on their own, and longer-lasting ones can generally be removed if they cause trouble.
Persistent watering, gritty eyes, or crusty lids are worth investigating rather than living with, especially since the fix is often simple once the cause is identified. If either of these has been bothering you, it is a good reason to book with an eye doctor who accepts your vision coverage.