Corneal Pachymetry: Measuring Corneal Thickness for Glaucoma and LASIK
Updated: 2 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026 · How we review
Quick Answer
A corneal pachymetry test is a quick, painless test that measures the thickness of the cornea, the clear dome at the front of the eye. It's important for glaucoma care, because corneal thickness affects eye pressure readings and a thinner cornea is linked to higher glaucoma risk. It's also required before LASIK. Results are available right away.
What the research says
A thin cornea predicts glaucoma: in the large Ocular Hypertension Treatment Study, a thinner central cornea was a powerful predictor of developing glaucoma, along with age, eye pressure and optic nerve findings (Gordon MO et al., Arch Ophthalmol, 2002) [2]
Thickness changes eye pressure readings: a review of 300 data sets found the average healthy central cornea was 534 microns thick, and a 10% difference in thickness changed measured eye pressure by about 3.4 mm Hg across all eyes studied, but only about 1.1 mm Hg in healthy eyes (Doughty MJ et al., Surv Ophthalmol, 2000) [3]
Key takeaways
Pachymetry measures how thick your cornea is.
Typical central thickness is about 540 to 550 microns.
A thin cornea can make eye pressure read falsely low and is linked to glaucoma risk.
It's required before LASIK to make sure the cornea is thick enough.
The test takes seconds and results are immediate.
What is pachymetry?
The cornea focuses light into the eye. Its thickness matters for several reasons. Eye pressure tests such as tonometry press on the cornea, so a thick cornea can make pressure look higher than it is, and a thin cornea can make it look lower. Refractive surgery removes corneal tissue, so surgeons need enough thickness to do it safely. Swelling or thinning can also signal corneal disease. Sources: [1]
Why it's done
Corneal thickness guides several eye care decisions.
Diagnosing and treating glaucoma.
Planning LASIK or other refractive surgery.
Monitoring corneal diseases such as keratoconus, Fuchs' dystrophy and corneal hydrops.
Assessing eye injuries.
Interpreting eye pressure readings. Sources: [1]
Types of pachymetry
Both take several readings and report the average.
Type | How it works | Touches the eye? |
Optical | Light or optical coherence tomography (OCT) images the cornea | No |
Ultrasonic | A small probe uses sound waves after numbing drops | Yes, for a few seconds |
Sources: [1]
How the test is done
No preparation is needed.
Optical: you rest your chin and forehead on a machine while it captures images.
Ultrasonic: numbing drops are placed, and a sterile probe gently touches the center of your cornea for a few seconds.
The device takes several measurements and reports the average. Sources: [1]
Risks
Optical pachymetry has no known risks. Ultrasonic pachymetry may rarely cause eye irritation, infection, a reaction to the numbing drops or a temporary scratch on the cornea. Avoid rubbing your eyes until the numbing wears off. Sources: [1]
What the results mean
Your eye doctor interprets results with your other tests.
Result | What it may mean |
About 540 to 550 microns | Typical central thickness |
Thinner than average | Eye pressure may read falsely low; higher glaucoma risk; may limit refractive surgery |
Thicker than average | Eye pressure may read falsely high; can occur with corneal swelling |
Results are available right away. A thickness outside the typical range doesn't necessarily mean your eye is unhealthy. Surgeons check that the cornea is thick enough to lower the risk of corneal ectasia, when the cornea bulges forward after surgery. Sources: [1, 2, 3]
Conclusion
Corneal pachymetry is a fast, painless measurement with big implications. It helps your eye doctor interpret eye pressure, judge glaucoma risk and decide whether refractive surgery is safe for you.
Keep learning: read about glaucoma tests and corneal topography.
Frequently asked questions
What is pachymetry?
A test that measures how thick your cornea is.
What is a normal corneal thickness?
About 540 to 550 microns in the center.
Why does corneal thickness matter for glaucoma?
It affects eye pressure readings, and a thin cornea is linked to higher risk.
Is pachymetry needed before LASIK?
Yes. Surgeons check that the cornea is thick enough.
Does pachymetry hurt?
No. Ultrasonic testing uses numbing drops.
How long does it take?
Just seconds to a few minutes.
Does the probe touch my eye?
Only with ultrasonic pachymetry, for a few seconds.
Do I need to prepare?
No preparation is needed.
When will I get results?
Right away.
What is corneal ectasia?
A bulging of the cornea that can happen if it's too thin after surgery.
Related Reading
Glaucoma Tests: Types, What to Expect and What Results Mean tests used to diagnose glaucoma.
Corneal Topography: Mapping the Cornea and Reading the Results mapping of the cornea's shape.
Keratometry: Measuring Corneal Curve for Astigmatism and Cataract Surgery a measurement of corneal curvature.
Eye Exam: What Happens, Tests Included and How Often to Go a full check of your eye health.
Glaucoma: The Silent Threat to Vision, and How Early Treatment Can Protect Your Sight the eye disease pachymetry helps assess.
References
Cleveland Clinic. Corneal Pachymetry Test: What It Is, Normal Range & FAQs. Cleveland Clinic. Last updated February 21, 2024. https://my.clevelandclinic.org/health/diagnostics/pachymetry-test
Gordon MO, Beiser JA, Brandt JD, et al. The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120(6):714-720. PMID 12049575. https://doi.org/10.1001/archopht.120.6.714
Doughty MJ, Zaman ML. Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach. Surv Ophthalmol. 2000;44(5):367-408. PMID 10734239. https://doi.org/10.1016/s0039-6257(00)00110-7
Medical disclaimer
This article is for general education only and does not replace advice from a qualified healthcare professional. Talk to your doctor about your own diagnosis and treatment, and seek emergency care right away for severe or sudden symptoms.
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