LASIK Eye Surgery for Astigmatism

If you have astigmatism, you may be able to have LASIK eye surgery. LASIK is a type of refractive surgery used for correcting refractive errors such as astigmatism, myopia, and hyperopia. If you have astigmatism, your vision may be blurry at a distance as well as near. You may feel tired after reading and find that letters and words appear to be slanted. Many people with astigmatism have found LASIK eye surgery to be a safe and effective method of vision correction.

For some reason, there is a "stigma" about astigmatism when it comes to LASIK. However, most patients with astigmatism can have laser refractive surgery. Most of this stems from the fact that is was the first type of vision problem approved by the FDA for LASIK.

Female patient undergoing laser eye surgery
Portra / Getty Images

Overview

Astigmatism is often misunderstood. It is a vision problem usually caused by the cornea, the clear dome-like structure on the front part of the eye, having a shape similar to a football rather than a basketball. So, there is more power or more curvature in one meridian, for example at 90 degrees, than there is at the opposite meridian at 180 degrees. While the majority of astigmatism is most often corneal astigmatism, one can also have lenticular astigmatism. The cornea may be perfectly round or spherical, but the lens inside the eye has astigmatic power.

How It's Measured

Astigmatism is measured with a corneal topographer. A corneal topographer is a machine that projects a disc of lights onto the cornea. Data that is reflected back shows the curvature over the entire cornea which is used to calculate the amount and direction of astigmatism. The amount of power that is needed to correct astigmatism is measured with a phoropter, the instrument used when the doctor asks, "Which one is better, one or two?" Doctors also use a wavefront aberrometer to see how astigmatism affects the quality of your vision.

Other Ways to Correct Astigmatism

While most people who have astigmatism can have LASIK, some people have too much astigmatism for the laser to correct. In this case, there are two procedures that fall under the category of corneal relaxing incisions (CRIs)—astigmatic keratectomy (AK) and limbal relaxing incision (LRI).

With AK, a skilled refractive surgeon makes small incisions in certain key places in the cornea to make the cornea more spherical. An LRI is made at the opposite edges of the cornea which causes a slight flattening in that direction.

The surgeon must evaluate the pros and cons of each in conjunction with the needs of each individual patient.

The pros of LRIs include:

  • Easier to perform, less dependent on pachymetry, less likely to result in overcorrections, quicker post-op stabilization of refraction, postoperative topography is smoother/more homogenous (coupling).
  • LRIs are best for low to moderate amounts of astigmatism (< 3 diopters).

The cons of LRIs include:

  • A larger incision (typically one or two incisions 1-3 clock hours in arc length)

The pros of AKs include:

  • Shorter incision, more powerful (correct a larger amount of astigmatism), placement in smaller optical zone (therefore low coupling ratio), 'multifocal' effect (better depth of focus)

The cons of AKs are:

  • More discomfort, greater risk of corneal perforation (more dependent on accurate pachymetry), may cause more corneal irregularity and irregular astigmatism
  • AKs have been noted to have a higher risk of overcorrection so they are more often performed on patients with higher amounts of astigmatism.
  • AKs may also risk a loss of best-corrected spectacle acuity

A Word From Verywell

A thorough evaluation of your vision will be required to determine if you are a candidate for LASIK. The type and severity of your astigmatism will help your ophthalmologist decide if LASIK eye surgery will be beneficial to you. Some people with astigmatism should not have LASIK, as some qualities and characteristics of their eyes prevent them from having a successful outcome.

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Article Sources
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  1. Mayor S. People considering laser eye surgery should be warned of risks, says NICE. BMJ. 2006;332(7544):746. doi:10.1136/bmj.332.7544.746-b

  2. American Optometric Association. Astigmatism.

  3. American Academy of Ophthalmology. What is astigmatism? Updated August 31, 2018.

  4. Accuvision- The Eye Clinic. Aberrometer.

  5. Cincinnati Eye Institute. Limbal relaxing incisions.

Additional Reading
  • Azar, Dimitri T. and Douglas D. Koch. "LASIK: Fundamentals, Surgical Techniques, and Complications." Marcel Dekker, Inc. 2003.