Are You a Good Candidate for LASIK Surgery?

While LASIK surgery is generally a safe and effective treatment for several common vision problems, it's not for everyone.

If you're considering LASIK surgery, you should undergo a thorough examination by an ophthalmologist to determine if you're a good candidate for the procedure. The exam should include a discussion of your medical history as well as your lifestyle.

This article explains the three problems LASIK is designed to fix, the potential side effects of the surgery, who is likely to benefit from LASIK surgery, and the seven eye tests that will help you and your eyecare provider decide if LASIK is right for you.

Woman getting LASIK surgery
Sean Locke

LASIK Basics

LASIK is an acronym for Laser-Assisted In Situ Keratomileusis. It is a surgery that reshapes the cornea—the clear, round dome at the front of your eye—to correct three eye problems:

  • Nearsightedness (myopia), or when your distance vision is blurry (and close-up vision is clear). This means the cornea is more curved than normal.
  • Farsightedness (hyperopia), or when your close-up vision is blurry (and your distance vision is clear). This means the cornea is too flat.
  • Astigmatism, or when vision is blurred or distorted because the cornea is shaped irregularly.

During LASIK surgery, a surgeon makes a small flap in the cornea and folds it back. Then they use a laser to reshape the cornea and fold the flap back. The surgery is quick—about 15 minutes for each eye—and relatively painless.

LASIK surgery has a hugely successful track record, particularly among people who are nearsighted. Studies suggest that 94% of moderately nearsighted people walk out of the procedure with 20/40 vision or better (20/20 vision is the ideal). Seventy percent of patients go on to enjoy 20/25 vision or better.

Potential Side Effects

Every type of surgery carries its share of risks. Most side effects of LASIK eye surgery resolve after a few weeks or months. You should be aware of them to make an informed decision about whether to have the surgery. Potential side effects include:

  • Flap problems, particularly infection and excess tears from folding back the flap during the surgery
  • Glare, halos and double vision, which can make seeing at night a challenge
  • Under-correction, which can happen if too little tissue is removed from the eye. If this happens, another surgery (an "enhancement") may be necessary.
  • Over-correction, which happens when too much tissue is removed. An over-correction is trickier to fix than an under-correction.
  • Astigmatism, which can be caused by uneven tissue removal. Glasses, contact lenses, or another surgery might be necessary.
  • Corneal ectasia, a bulging and thinning of the cornea. Treating this may mean corrective glasses or contact lenses.
  • Vision loss or changes, which can leave some people unable to see as clearly as they did before. Still, these changes are rare.

Dry Eye After LASIK

One study found that half of LASIK patients experienced dry eye one week after LASIK surgery. The percentage fell to 40% after one month and then again to between 20% and 40% of patients six months after surgery. Dry eye can be treated with eye drops.

Good Candidates for LASIK

It's likely that LASIK's impressive track record is partly due to proper vetting, meaning only people who meet certain criteria can have the surgery. Candidates for LASIK surgery must be healthy adults who are 21 years old or older and have used the same eyeglass or contact lens prescription for at least a year.

On the other hand, LASIK is often discouraged among people who:

  • Are pregnant or nursing
  • Have fluctuating hormones due to a disease like diabetes
  • Take medications that may cause vision fluctuations

This doesn't mean that everyone else gets a green light to proceed with LASIK surgery. The Missouri Eye Institute says that "most surgeons will want to ensure that acute or chronic conditions are adequately managed or stabilized before approving someone for LASIK surgery." Some of these conditions include:

If you're dealing with one of these issues, you should still go ahead with the LASIK prequalification tests and work with your ophthalmologist to keep your eyes healthy.

Prequalification Tests for LASIK Surgery

Your eyecare provider will need to perform these tests to help determine whether you should proceed with LASIK surgery.

Prescription Check

Before LASIK, an ophthalmologist may use cycloplegic eye drops. These drops temporarily paralyze the focusing muscle inside your eye. This allows the ophthalmologist to measure your total prescription without forcing you to focus too hard. Basically, it lets the ophthalmologist collect the raw data of your true vision.

Eye Muscle Test

A binocular vision assessment is a vision test that checks how your eyes work together as a team. Your ophthalmologist will want to ensure that you do not have a binocular vision disorder, in which the eyes cannot merge the images into one in the brain.

The disorder can result in a wide array of vision problems, from dizziness and double vision to light sensitivity (photophobia) and poor depth perception. Such a disorder may interfere with positive LASIK results, so your ophthalmologist will want to eliminate it as a risk factor.

Tear Analysis

Qualitative and quantitative tear film tests examine your natural tears. If either one of these measures is not optimal, your ophthalmologist may choose to delay the LASIK procedure until the quality or quantity of your natural tears can be corrected.

Cornea Measurements

Corneal topography is exactly what you would expect it to be: A computerized method of determining the exact shape of the cornea. Measurements are computed and placed into color maps. Hotter colors, such as red, show steeper areas while cooler colors show areas that are flatter.

Some patients have a corneal shape that does not pose problems before LASIK, but could put them at risk for developing a corneal disease, such as keratoconus, after having LASIK. This disease occurs when the cornea thins out and gradually bulges outward to form a cone shape.

Wavefront Analysis

Wavefront analysis is a relatively new development in eye care and can be very important to measure vision deficits known as higher-order aberrations. These are similar to lower-order aberrations, such as nearsightedness, farsightedness, and astigmatism. In all these aberrations, imperfections of the cornea can cause distorted vision.

Higher-order aberrations seem to be more apparent in some patients and often cause symptoms such as decreased night vision, glare, and halos around lights.

Corneal Thickness Measurement

A corneal thickness measurement (also known as pachymetry) discloses the thickness of the cornea and whether it's swollen. This quick and easy measurement is important for potential LASIK patients since the surgery depends on the health of the cornea. People with extremely thin corneas, for example, may not make good LASIK candidates.

Pupil Size Measurement

People with naturally large pupils or pupils that dilate heavily in dim light may experience more glare, halos, and contrast problems after having LASIK surgery. However, with today's laser techniques, this tends to be less of a problem.

Nonetheless, pupil size is measured with special devices, such as an infrared pupillometer, so that a better surgical plan can be devised.

Summary

LASIK is an acronym for laser-assisted in situ keratomileusis—a surgery that reshapes the cornea to correct nearsightedness, farsightedness, and astigmatism. LASIK surgery presents the risk of some side effects, but most resolve after a few weeks or months.

Healthy adults over age 21 who have used the same eyeglass or contact lens prescription for at least a year generally make good candidates for LASIK surgery. Those who are pregnant or nursing, deal with fluctuating hormones due to disease, or take medications that may cause vision changes generally do not.

Eyecare providers perform several prequalification tests to be certain that LASIK is right for you.

A Word From Verywell

If you're considering LASIK surgery, you'll need to devote some upfront time to prequalifying tests. But the time and care that goes into preparing for the surgery usually means successful results. Taking the long view on LASIK may add value to your experience.

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9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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