Why Is Corneal Thickness Important for LASIK?

Why Is Corneal Thickness Important for LASIK?

May 30, 2022

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Laser-assisted in situ keratomileuses (LASIK) is the best known and most commonly performed refractive surgery. LASIK is an FDA-approved laser procedure used to correct refractive errors, like myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.

In order to have LASIK, you’ll need a consultation to assess your candidacy. As part of this, your corneal thickness will be measured. Corneal thickness for LASIK must be sufficient to proceed with surgery. In LASIK eye surgery, a thin cornea is not safe.

Why Is Corneal Thickness Important?

The cornea is the clear tissue at the front of the eye. It’s sometimes called the window into the eye, as you can see the iris through it. The shape of the cornea affects refractive error; therefore, by modifying the shape of the cornea, a refractive error can be treated. This is done using laser ablation, which means tissue removal.

The reason there is a specific corneal thickness required for LASIK is to ensure there will be sufficient tissue remaining after part of it is removed. In other words, in laser eye surgery corneal thickness is decreased. It must be thick enough initially to withstand this decline. The thin cornea LASIK risk is simply not worth it.

Corneal Thickness Requirements for LASIK

Corneal thickness is measured in micrometers, or microns. Normal corneal thickness in microns is approximately 555. The flap that is created by the femtosecond laser in LASIK is approximately 110 microns. After the flap is created and lifted, tissue is removed by the laser ablation. There must be sufficient tissue remaining after the creation of the flap and the removal of tissue for the correction of refractive error.

The remaining tissue is often referred to as the residual stromal bed and should measure 250 microns at a minimum. This tissue serves to maintain the stability of the cornea. The higher the refractive error, the more tissue needs to be removed by the laser ablation. Therefore, for LASIK to be safe, a patient with a pre-treatment refractive error of -8.00 will need a thicker cornea than someone with refraction of -3.00.

In your preoperative evaluation, you’ll get a corneal thickness test for LASIK called pachymetry. This will help to determine if you have thinner or thicker than the average corneal thickness and whether you meet the LASIK minimum corneal thickness. Put simply, a thin cornea and LASIK don’t mix.

What If My Cornea Is Too Thin for LASIK?

What If My Cornea Is Too Thin for LASIK?

If you have a cornea too thin for LASIK, you’ll be advised that it is not safe to proceed with the surgery. Although it may not be what you want to hear, your doctor is advising you on what’s best for your safety. There are substantial risks of LASIK with thin corneas. Thin cornea LASIK is unsafe and could lead to worsening of vision.

Alternatives To LASIK For Thin Cornea

If you don’t meet the requirements for LASIK eye surgery corneal thickness, there are alternative options that you may consider.

Instead of removing tissue from the cornea, a biocompatible synthetic lens is inserted through the cornea. The lens sits between the iris (the colored part of the eye) and the crystalline lens. The prescription of the ICL will be calculated beforehand and will be specific to the patient’s visual needs.

This laser refractive surgery is similar to LASIK but doesn’t require the creation of a flap. This spares tissue, and therefore PRK can often be performed on thinner corneas than LASIK. PRK is a quicker procedure than LASIK but can take a little longer to heal. Unlike LASIK, PRK is done one eye at a time.


Cornea thickness measurement is a very important part of screening for LASIK. To avoid complications, your doctor will need to make sure that your preoperative corneal thickness is sufficient.

Contact Kraff Eye Institute of Chicago today to see if you’re a good candidate for the procedure. And if you’re advised that LASIK isn’t the best option for you, ask about PRK and ICL.

With decades of experience and a commitment to using the latest technological advances, Dr. Kraff can make a trusted recommendation on which refractive procedure is best for you.

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