If your eyes burn, sting or feel gritty by mid-afternoon, an eye doctor will want to know whether you are actually making enough tears. Symptoms alone cannot answer that, because a dry eye and an overwatering eye can feel surprisingly similar.
One of the oldest and simplest ways to check is the Schirmer test. It uses a strip of paper, five quiet minutes, and a ruler printed along the edge.
Here is what the test measures, what the appointment feels like, and how much weight the number really carries.
What the strip is actually measuring
Tears are not just water. A healthy tear film has an oily outer layer from glands in the eyelid margins, a watery middle layer from the lacrimal glands, and a mucus layer that helps the whole thing stick evenly to the surface of the eye.
The Schirmer test looks at one part of that system: the watery portion. A narrow strip of filter paper is tucked into the lower lid, and tear fluid travels along it the way water climbs a paper towel.
How far the wetting front moves in a set amount of time gets read off in millimeters. That distance stands in for how much watery tear your eyes are producing during the test.
Because it looks at volume only, it says nothing about the oily layer. Plenty of people with real dry eye symptoms produce enough water but lose it too fast, and this test will not catch that on its own.
Why a doctor orders it
The usual trigger is a set of complaints that have not responded to over-the-counter tears: burning, sandiness, redness by evening, blurring that clears when you blink, trouble wearing contact lenses, or eyes that water constantly for no obvious reason.
Constant watering confuses people, and it is a common reason for testing. When the surface is irritated and undersupplied, the eye can respond with bursts of reflex tearing that spill over the lid and do nothing useful.
Tear testing also comes up in other situations, including:
- Before or after eye surgery, since a dry surface affects healing and comfort
- When a medication known to reduce tearing has been started
- When an autoimmune condition affecting glands is being investigated
- When symptoms are lopsided, with one eye far worse than the other
What the five minutes are like
Contact lenses come out first, and eye makeup around the lower lid is usually wiped away. Your doctor may use numbing drops beforehand, or may skip them, and the choice changes what the result means.
With numbing drops
Anesthetic quiets the reflex tearing that the paper itself would otherwise provoke. The idea is to capture what your eyes produce at rest, on their own, rather than a startled response to something touching them.
Without numbing drops
Skipping the drops measures baseline production plus whatever reflex the strip triggers. It can be useful, but it typically returns a higher number and is more variable from visit to visit.
Either way, the strip is folded at one end and rested inside the lower lid, off to the outer side so it is not sitting against the cornea.
Then you close your eyes, or sometimes look slightly up, and wait. Five minutes is the standard interval. The strips come out, and the wet portion is read against the printed scale.
How the number is read
Results are given in millimeters of wetting per eye. Higher numbers mean more watery tear reached the strip.
Broadly, a generous reading suggests production is not the problem, a middling reading suggests it may be part of the picture, and a very low reading points toward genuinely reduced output. Your doctor will tell you which band your eyes fell into and what the cutoff was, since practices differ slightly and the numbers shift depending on whether anesthetic was used.
Ask for your actual figures and write them down. They are far more useful next year as a comparison point than as a standalone verdict today.
Why one result is not a diagnosis
Tear testing is noisy. The same eyes can give different readings on different days, and several things can nudge the outcome:
- Room humidity, air conditioning and how long you spent on a screen beforehand
- How the strip was placed and whether you peeked or blinked hard
- Antihistamines, some blood pressure drugs, hormonal changes and other medications
- Age, since baseline production tends to drift down over the years
That is why a low number by itself does not name a condition, and a normal number does not dismiss your symptoms. The result is one input alongside your history and what the doctor sees at the microscope.
The tests that sit alongside it
Most dry eye workups combine several quick checks. A doctor may put a dye in the tear film and time how long the film holds together before it breaks up, which speaks to the oily layer rather than the watery one. Dyes also reveal dry patches on the surface that would otherwise be invisible.
Other options include measuring the small reservoir of tear that sits along the lower lid margin, testing the saltiness of the tear film, examining the lid glands directly, or using a fine thread instead of paper for a much shorter test.
None of these replace each other. Together they help sort out whether you are making too little tear, losing it too quickly, or dealing with lids and glands that need their own treatment.
Common questions
Does the Schirmer test hurt?
It is usually described as strange rather than painful. The strip feels like something in the eye, and mild watering or brief redness afterward is normal.
Can I drive home afterward?
Usually yes, though numbing drops leave the eye unprotected for a while and dye can blur things briefly. Ask before you leave, and do not rub your eyes until sensation is fully back.
Should I stop my eye drops before the test?
Ask when you book. Doctors often want lubricating drops paused for a set period beforehand so the reading reflects your own tears, but never stop a prescribed drop on your own.
A tear test is a snapshot, not a sentence. The value comes from pairing that number with an exam and a real conversation about your symptoms, your work environment and your medications. If your eyes have been uncomfortable for weeks and you have been managing it out of a bottle, it is worth getting looked at properly. You can search for an eye doctor in your plan's network and start there.