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LASIK and Corneal Thickness

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Johnny Khoury, M.D.

Medically Reviewed by Johnny Khoury, M.D.

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If you no longer want to wear glasses or contact lenses to treat your nearsightedness, farsightedness or astigmatism, LASIK surgery is a great alternative. Rather than simply compensating for the corneal aberrations that cause these lower-order refractive errors, LASIK actually corrects the corneal aberrations, thereby providing patients with clear vision.

To correct the corneal irregularities that cause nearsightedness, farsightedness and astigmatism, a surgical procedure is required. At Teplick Custom Vision, an NVISION Company, I perform LASIK surgery to help patients achieve clear, unaided vision.

To be considered a good candidate for LASIK, patients must meet several requirements, including meeting the corneal thickness guidelines. In this blog post, I’ll discuss LASIK and corneal thickness so you understand why this requirement is so important.

The LASIK Procedure

Nearsightedness, farsightedness, and astigmatism happen when the shape of the cornea is too flat, too steep or irregular. When eyes process images, these defects can result in light being directed in front of or behind the retina, rather than directly on it.

During LASIK surgery, we’ll numb your eyes with drops and put an eyelid holder in place so you don’t blink.

We then make an incision to create a flap in the outer layer of the cornea and roll it away to expose the remaining cornea.

With the flap open, we’ll use a laser to reshape the stromal layers of your cornea—achieving the precise shape upon which light can directly reflect off the retina and produce clear vision. During this process, you’ll hear clicking sounds. That’s the sound of the laser doing its work.

Once we achieve the ideal cornea shape, we fold the flap back into place. The flap will set on its own in a couple minutes, and healing will start.

Why Is Corneal Thickness Important?

Because LASIK surgery requires the creation of a LASIK flap, patients must have a sufficiently thick cornea. If the patient does not have enough corneal thickness to support the flap, they are more likely to experience post-surgery complications such as corneal ectasia, a bulging of the cornea that can actually worsen vision.

Because patient safety is a priority, we do not perform LASIK on patients who have thin or weak corneas.

Corneal Thickness Guidelines

After LASIK surgery, the patient should have a minimum of 250 microns of corneal thickness remaining (flap thickness not included. However, most surgeons are leaving a minimum of 300 microns. The surgery involves:

  • About 90-120 microns of tissue for the corneal flap, using femtosecond laser technology (Zeimer/Z LASIK)
  • The removal of 12 to 15 microns per diopter of vision corrected

To calculate how much corneal tissue you will have left after your LASIK surgery, I’ll measure your corneal thickness with the corneal pachymetry test. Patients stare straight ahead while the device is placed next to the eye and ultrasonic technology measures the cornea.

In addition, I’ll measure the degree of your refractive error and the amount of prescription power needed to correct it. Then I’ll determine how much tissue will need to be removed to achieve improved vision.

For example, if you have a -6.00-diopter prescription power, 72 to 90 microns of corneal tissue would be removed during your LASIK surgery. Add this to the 120 microns for the corneal flap, plus the 300 microns that must be remaining after surgery, and you would need at least 492 to 510 microns of corneal tissue before LASIK to be considered a good candidate for surgery with a -6.00-diopter prescription power. In addition, most surgeons will avoid doing LASIK for corneas less than 470 microns and will consider going PRK instead.

For most patients, the cornea is 540 to 550 microns thick.

LASIK Success Rates

It might surprise you to learn that LASIK surgery is not only the most successful eye surgery in the United States—but it is also the most successful elective surgery among all surgeries! The success rate for LASIK is 96%. And about 9 out of 10 people who have LASIK end up with vision between 20/20 and 20/40—without glasses or contact lenses.

After surgery, you probably will experience a bit of discomfort, but unless you develop complications, you should be back to normal within a few days.

If Corneas Are Too Thin

Patients with natural thin corneas, and those with high prescription powers may not have sufficient corneal thickness for LASIK surgery. However, these patients may be good candidates for PRK surgery. Contact us today at
877-455-9942.

to learn more about your vision correction options and to book a free LASIK consultation.

References

  1. LASIK success rates. (October 23, 2017). American Refractive Surgery Council.
  2. Dry eye syndrome. (September 24, 2020). Mayo Clinic.
  3. What are Cataracts. (July 7, 2021). American Academy of Ophthalmology.
  4. Good candidates for LASIK. (April 2018). American Refractive Surgery Council.
  5. When is LASIK not for me? (July 2018). Food and Drug Administration.
  6. LASIK – Laser Eye Surgery. (October 21, 2020). American Academy of Ophthalmology.
Johnny Khoury, M.D.
Medically Reviewed by Johnny Khoury, M.D.

Dr. Johnny Khoury, a Johns Hopkins and Washington University double fellowship trained surgeon, is among the world’s most experienced refractive surgeons. His experience in excimer laser refractive surgery dates back to 1994.

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