Purpose of LASIK Eye Surgery

Laser-assisted in situ keratomileusis (LASIK) is a type of eye surgery done to correct certain refractive errors that lead to overall blurriness or a hampered ability to see objects at different distances. LASIK reshapes the cornea in order to permanently improve your vision.

Laser eye surgery

Diagnosis Related to LASIK Eye Surgery

Your cornea is a clear, dome-shaped tissue that covers the front of your eye. It is mainly responsible for bending ("refracting") light rays as they enter the eye. This refraction allows light rays to focus precisely on your retina (located at the back of your eye), so that you can see clearly and sharply.

A refractive error is caused by an abnormally shaped cornea, an eyeball that is too long or short, or an aging lens. It results in light rays not being focused properly on the retina, making your vision blurry.

The three main types of refractive errors corrected by LASIK are:

  • Nearsightedness (myopia): When a person can only see close by objects clearly (objects far away are blurry)
  • Farsightedness (hyperopia): When a person can only see far away objects clearly (objects close by are blurry)
  • Astigmatism: When images are blurry, whether they are near or far

LASIK does not correct a type of refractive error called presbyopia. This eye condition causes farsightedness and occurs as a result of the natural hardening of the lens with age.

LASIK is not considered medically necessary. Rather, it is an elective procedure for those who want an alternative to corrective eyewear.

While most people can forego their eyeglasses and contact lenses after LASIK eye surgery, this may not be the case for the rest of their lives. This is because as people age, their eyes naturally change, making tasks like reading and seeing nearby objects more difficult.

Criteria and Contraindications

Even if you have been diagnosed with nearsightedness, farsightedness, or astigmatism, you may not be a candidate for LASIK.

Basic criteria for undergoing LASIK surgery include the following:

  • You are at least 18 years old
  • Your refractive error must not be too large
  • Your refractive error must be stable for longer than one year (this means that your eyeglass or contact lens prescription has not changed by much in the last year)

Absolute contraindications to undergoing LASIK surgery include the following conditions:

  • A thin cornea: This is important because the surgeon cuts and reshapes the cornea during LASIK.
  • Corneal ulcerations
  • A cone-shaped cornea (called keratoconus)
  • Dry eye syndrome: A healthy tear film coating is needed to ensure proper healing of the cornea after LASIK.
  • Certain external eye diseases, like blepharitis or allergic eye disease
  • Pregnancy or breastfeeding
  • A significant cataract
  • Uncontrolled diabetes mellitus
  • Advanced or uncontrolled glaucoma
  • An uncontrolled autoimmune disease (e.g., Sjögren's syndrome)
  • Unrealistic expectations of your visual outcomes

Using certain medications, like high doses of a steroid (e.g., prednisone), or actively participating in contact sports where you are at risk for getting hit in the eye (e.g., boxing), may also disqualify you as a LASIK candidate.

Other possible contraindications to undergoing LASIK surgery include:

  • A controlled autoimmune disease (e.g., lupus or rheumatoid arthritis)
  • History of abnormal wound healing
  • History of herpetic keratitis
  • Diabetes (even if controlled)
  • Glaucoma (even if controlled)
  • A history of prior refractive surgery

While not an outright contraindication, people with larger pupils are also at a greater risk for having night vision problems, like seeing glares or halos around lights, after LASIK eye surgery.

Tests and Labs

During your two- to three-hour pre-op appointment, your ophthalmologist or optometrist will review your medical history and medication list. They will also perform several sophisticated tests that will give them the information they need regarding your overall eye health.

In addition to helping them determine if you are a good candidate for LASIK eye surgery, the information from the tests will help guide the surgeon once they are performing your procedure.

Stop wearing soft contact lenses for two to three weeks and hard lenses for three to four weeks before your consultation. Contact lenses can temporarily alter the shape of your cornea, which will affect your evaluation.

The preoperative tests for LASIK usually include the following:

  • Refraction test: Measurements are made to determine your prescription, and your eye practitioner will dilate your pupils to make the test more accurate.
  • Dry eye test to evaluate the composition and volume of the tear film coating of the eye
  • Pachymetry to measure the thickness of the cornea
  • Wavefront analysis: This is used to more precisely understand distortions and irregularities of the eye, known as higher-order aberrations. This information can be helpful during the surgery, as it provides data about a patient's unique visual system.
  • Corneal topography: A computer-assisted tool creates a map of the shape of the cornea. This test can be used to detect corneal abnormalities that may be a contraindication to undergoing LASIK surgery.
  • Pupil size measurement: Your pupil size will likely be measured with a special device called an infrared pupillometer.

Separate medical tests, like laboratory tests or an evaluation by a patient's regular healthcare provider may or may not be necessary for LASIK surgery, based on your eye doctor's specific protocols.

A Word From Verywell

You may decide you want to proceed with LASIK soon after hearing it's an option for you, or you may want to take some time to make your decision. Depending on the surgeon or medical facility, you may wait weeks or months for a scheduled surgery date.

Be sure you have the information you need to feel comfortable with your choice. Your healthcare provider can help you weigh the risks and benefits of the procedure and tell you what you can realistically expect coming out of the surgery in terms of your individual vision improvement.

7 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.
  1. National Eye Institute. (July 2019). Refractive Errors.

  2. American Refractive Surgery Council. (July 2017). Your LASIK Consultation: A Deeper Look Into What To Expect

  3. Wilkinson JM, Cozine EW, Khan AR. Refractive Eye Surgery: Helping Patients Make Informed Decisions About LASIKAm Fam Physician. 2017 May 15;95(10):637-644.

  4. U.S. FDA. (July 2018). When is LASIK not for me?

  5. Wilkinson JM, Cozine EW, Khan AR. Refractive Eye Surgery: Helping Patients Make Informed Decisions About LASIKAm Fam Physician. 2017 May 15;95(10):637-644.

  6. Wilkinson JM, Cozine EW, Khan AR. Refractive Eye Surgery: Helping Patients Make Informed Decisions About LASIKAm Fam Physician. 2017 May 15;95(10):637-644.

  7. Boyd K. (December 2019). American Academy of Ophthalmology. LASIK — Laser Eye Surgery.

By Troy Bedinghaus, OD
Troy L. Bedinghaus, OD, board-certified optometric physician, owns Lakewood Family Eye Care in Florida. He is an active member of the American Optometric Association.