How Does Cornea Thickness Affect the Outcome of LASIK?

December 9, 2022 | LASIK, Vision Correction

LASIK is the most widely known and used procedure for vision correction in the United States. Laser assisted in situ keratomileusis (LASIK) can be used to treat nearsightedness (myopia), far-sightedness (hyperopia), and astigmatism and is an excellent alternative to glasses or contact lenses for many people. In a LASIK procedure, an eye doctor uses advanced laser technology to reshape a patient's cornea in order to improve vision without glasses.

While most people are good candidates for LASIK, it is not the most ideal vision correction procedure for everyone. Safety is our number one priority at ClearSight, and this is why we thoroughly examine and evaluate each patient's eyes to make sure they will have a successful laser vision correction outcome. The number one reason why a patient does not qualify for LASIK has to do with their corneal thickness. In this article, we will discuss why corneal thickness is important and how it affects the outcome of LASIK.

If you are tired of the hassles of glasses, contacts, and blurry vision, we can help you break free. To find out if you are a candidate for LASIK, call our experienced team at ClearSight today to schedule your consultation.

Can I have LASIK with thin corneas?

One of the first things we look at when a patient visits our ClearSight office for a LASIK screening is cornea thickness. What makes corneal thickness so important for LASIK? During a LASIK procedure, a tiny corneal flap is created with a femtosecond laser to allow an excimer laser to be used to reshape the cornea. The new corneal shape allows for precise image focusing onto the retina.

Your cornea must be thick enough to support the creation of the corneal flap and for the treatment. A small amount of corneal tissue is removed (laser ablation) during cornea flap formation, and the cornea could be excessively thin if there is not enough corneal tissue left over after creating the flap. A cornea that is too thin might lead to significant difficulties, including vision problems. LASIK can cause more harm than good if your cornea isn't thick enough.

It is important to make sure there is enough corneal tissue left after the procedure to guarantee the cornea is structurally stable since corneal tissue is permanently removed during the LASIK operation. This is why preoperative corneal thickness is so important and why people with thin corneas are normally told they are not a good candidate for LASIK.

What does my eyeglass prescription strength have to do with corneal thickness in LASIK?

There is no one size fits all approach to LASIK. Prescription strength is very important for the effectiveness of LASIK procedures. LASIK patients with successful outcomes most often have mild to moderate refractive errors that need to be corrected.

If you require a corrective lens with a stronger prescription, too much tissue may need to be removed in order to achieve the visual outcomes hoped for. You must have enough corneal tissue to create a cornea flap and enough cornea tissue to remove during the treatment in order to ensure that enough tissue is left in order for the cornea to remain stable after the treatment. For people with thin corneas, this is often not able to be achieved safely and effectively with a LASIK procedure.

How do I know if my corneal thickness is ideal for LASIK?

There is an evaluation process for LASIK that involves normal preoperative corneal topography and other tests since no one expects you to be aware of the thickness of your cornea. A corneal pachymetry test is used to measure your cornea's thickness as part of the initial LASIK screening.

Your cornea's thickness is measured by ultrasonic waves by placing an ultrasound pachymeter in the center of the eye. Normal corneal thickness in microns is approximately 555.

After LASIK, doctors prefer that a patient still have at least 250 microns of corneal tissue left over. This means that after creating the corneal flaps and applying the prescription, you need to have that much corneal tissue remaining.

The ideal preoperative corneal thickness for LASIK is typically between 450 and 550 microns. All of these measurements are taken during a LASIK consultation to help you, and your doctor determines if LASIK is the best vision correction procedure for you.

How much corneal tissue is removed during LASIK?

The flap thickness of the LASIK flap created by the surgeon is typically 120 microns. Depending on the treatment's diopter, our excimer laser will remove 14 to 16 microns of corneal tissue. Before the LASIK flap is repositioned, there should normally be at least 250 microns (m) of corneal tissue left over to guarantee the cornea is structurally safe.

What if my corneas are too thin for LASIK?

You will be advised that having LASIK is not safe if your cornea is too thin for the procedure. Your doctor is telling you what's best for your safety, even though it may not be what you want to hear. With thin cornea LASIK, there are a lot of substantial risks. LASIK on thin corneas is dangerous and may worsen eyesight. When the cornea's inner layers weaken, the cornea changes form, protrudes forward, and distorts your vision. This condition is known as corneal ectasia (Post-LASIK ectasia). This is an important reason why it is considered dangerous to perform LASIK surgery on a patient with thin corneas.

Thanks to advancements in technology and the field of ophthalmology, there are other refractive surgery alternatives you could consider to improve visual acuity if your corneal thickness doesn't meet the criteria for LASIK eye surgery.

  • EVO Visian ICL: A biocompatible synthetic lens is implanted via the cornea rather than tissue being removed. The intraocular lens is located between the crystalline lens and the iris, the colored portion of the eye. The prescription of the Visian ICL implants will be calculated in advance and tailored to the patient's visual requirements.
  • Advanced Photorefractive Keratectomy (ASA PRK): In contrast to LASIK, photorefractive keratectomy (PRK) does not require the development of a flap during the procedure. PRK removes the epithelium (outer layer) of the eye, and because less tissue is removed, PRK can frequently be performed on people with thinner corneas than LASIK. While PRK heals more slowly than LASIK, it is a quicker procedure.

At ClearSight, we are able to help 95% of people who walk through our doors with improved visual perception. We offer multiple vision correction procedures to make sure we can help almost everyone, including individuals who may have been told no in the past by other doctors. The best way to find out if you are a candidate for LASIK or any of our other procedures is to come in for your comprehensive exam. At your eye exam, we will take corneal topography maps, check your refraction (prescription), check for thin corneas, higher-order aberrations, and evaluate your overall eye health. It's time to see life clearly without contact lenses or glasses. For more information and to start your journey to clear vision, give us a call today to schedule your appointment.

“I wish I’d done it sooner!”

The number one thing we hear from our patients is that they wish they’d had LASIK sooner.

So the question for you is… why wait any longer?

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