Dry eye is diagnosed through a combination of symptom questionnaires, tear film measurements, and close examination of the eye’s surface. There’s no single test that confirms it on its own. Instead, eye doctors use a sequence of assessments, starting with your reported symptoms and then layering in objective tests to confirm the diagnosis and identify what type of dry eye you have.
Symptom Screening Comes First
Before any physical tests, your doctor will ask structured questions about your symptoms. Two standardized questionnaires are commonly used: the Ocular Surface Disease Index (OSDI) and the Dry Eye Questionnaire (DEQ-5). These aren’t just conversation starters. They produce a numerical score that helps classify severity.
The OSDI, for example, scores your symptoms on a scale of 0 to 100. A score of 0 to 12 is considered normal. Scores of 13 to 22 indicate mild dry eye, 23 to 32 suggest moderate disease, and anything from 33 to 100 points to severe dry eye. These scores also help track whether your condition improves over time with treatment. Before moving to diagnostic tests, your doctor will also ask screening questions to rule out other conditions that can mimic dry eye, such as allergies or infections.
Measuring Tear Film Stability
One of the most widely used tests is tear break-up time, or TBUT. Your doctor places a tiny amount of fluorescein dye on your eye, then watches through a microscope as you hold your eyes open without blinking. They’re timing how many seconds it takes for dry spots to appear in the thin layer of tears coating your eye.
In healthy eyes, the tear film stays intact for an average of about 27 seconds. A break-up time under 10 seconds suggests an unstable tear film. Values between 5 and 10 seconds are considered borderline, and anything under 5 seconds is a strong indicator of dry eye. Newer, non-invasive versions of this test use specialized instruments to measure stability without adding dye, which avoids the problem of the dye itself disrupting the tear film.
Testing Tear Production
The Schirmer test measures how much moisture your eyes actually produce. A small paper strip is hooked over your lower eyelid, and you close your eyes for five minutes. The strip wicks up tears, and the wet length in millimeters tells your doctor where you fall:
- Over 15 mm: normal tear production
- 10 to 15 mm: possibly dry
- 5 to 10 mm: moderately dry
- Under 5 mm: severely dry
This test is particularly useful for identifying aqueous-deficient dry eye, the type caused by your tear glands not producing enough of the watery component of tears. It can be done with or without numbing drops, and the version without anesthesia measures both your baseline tear production and the reflex tears triggered by the mild irritation of the strip.
Slit Lamp Examination
Your doctor will examine your eyes under a slit lamp, which is the microscope with a bright, narrow beam of light you’ve likely seen at eye appointments. They’re looking for several specific signs: superficial erosions on the cornea, redness of the white part of the eye, irregularities on the eye’s surface, and the overall health of the eyelid margins.
One key measurement taken during this exam is the tear meniscus height, which is the thin ribbon of tears sitting along the edge of your lower lid. A reduced tear meniscus suggests your eyes aren’t holding enough moisture. Your doctor will also examine the tiny oil glands lining your eyelid margins, checking for plugged openings, visible blood vessels along the lid edge, and crusty debris at the base of your lashes.
Staining the Eye’s Surface for Damage
Dyes applied to the eye reveal damage that’s invisible to the naked eye. Two dyes serve different purposes. Fluorescein highlights damage on the cornea (the clear front surface of your eye) by pooling in spots where the protective cell layer has broken down. It doesn’t stain healthy tissue, so any visible color indicates a problem. Lissamine green stains dead or damaged cells on the conjunctiva, the clear membrane covering the white of the eye and lining the eyelids. It’s better tolerated than older alternatives and gives a clearer picture of how much surface damage has occurred.
Doctors grade the staining patterns using standardized scales. The most common systems divide the cornea and surrounding tissue into zones and score each zone based on the density of stained dots. Higher scores, where individual dots merge into patches, indicate more advanced disease. These scores help your doctor gauge severity and monitor changes over time.
Tear Osmolarity Testing
Tear osmolarity measures the salt concentration in your tears. When your eyes are dry, tears become more concentrated, which itself causes irritation and further surface damage. A small sample of tears is collected from the lower lid margin using a handheld device, and the reading comes back in seconds.
A reading at or above 308 mOsm/L suggests mild dry eye. Some researchers have proposed that 316 mOsm/L is a more accurate cutoff. One useful feature of this test is that a large difference between your two eyes (greater than 8 mOsm/L) can itself be a sign of tear film instability, though this measurement is more useful alongside other tests than on its own.
Testing for Inflammation
A point-of-care test can detect whether inflammation is driving your dry eye. The test measures levels of a specific inflammatory protein in your tears. A small sample is collected from inside your lower lid, placed on a test strip, and results appear within minutes. A positive result means protein levels exceed 40 ng/mL, shown as two colored lines on the strip (similar to a pregnancy test).
This matters because inflammation is a core part of the dry eye cycle for many people, and a positive result may help your doctor decide whether anti-inflammatory treatments should be part of your plan. The protein measured becomes elevated within two hours of an inflammatory trigger, making it a useful early marker. Not every dry eye patient tests positive. Some people have dry eye driven more by nerve sensitivity than by active inflammation, and distinguishing between the two helps guide treatment choices.
Identifying the Type of Dry Eye
Once the basic diagnosis is confirmed, your doctor works to classify your dry eye as predominantly evaporative (the more common type, caused by oil gland problems in the eyelids) or aqueous-deficient (caused by insufficient tear production). Many people have a combination of both.
Evaporative dry eye is closely linked to meibomian gland dysfunction, a condition where the oil-producing glands in your eyelids become clogged or deteriorate. To evaluate this, your doctor may press gently on your eyelids to see whether the glands express clear, healthy oil or thick, toothpaste-like secretions. They may also perform meibography, an imaging technique that uses infrared light to photograph the glands through the eyelid. Healthy glands appear as long, parallel structures. Gland loss of more than 30% is a key diagnostic marker for evaporative dry eye caused by gland dysfunction.
The distinction matters because the two types respond to different treatments. Someone with primarily evaporative dry eye benefits most from therapies targeting the oil glands, while someone with aqueous deficiency needs approaches that increase or preserve the watery tear layer. A normal Schirmer test combined with poor gland function, reduced tear stability, and significant gland loss on imaging points clearly toward the evaporative subtype.