LASIK vs PRK vs SMILE: How the Laser Surgeries Differ

LASIK, PRK and SMILE all use a laser to reshape the cornea, the clear front of the eye, so it focuses light better. They differ in how the surgeon reaches the tissue. LASIK reshapes the cornea under a small flap, PRK removes the cornea's outer layer of cells first, and SMILE removes a small disc of tissue through a small incision, so no flap is made. PRK means a few sore days and a longer wait than LASIK for vision to settle, and it leaves no flap that could be dislodged later. An ICL (implantable collamer lens) is a different route: a lens placed inside the eye. Your corneas, prescription and tear film decide which one fits, and the surgeon makes the final call.

Key takeaways

All three laser surgeries reshape the clear front of the eye: LASIK under a small flap, PRK after removing its outer cells, and SMILE through a small incision.
PRK leaves no flap to knock out of place, but the eye may hurt for 1 to 2 days and vision takes longer to settle than after LASIK.
Laser surgery is probably not for you if your prescription changed in the past year, you're pregnant or breastfeeding, or you play contact sports.
When a prescription is too high or a cornea too thin for laser surgery, an implantable lens placed inside the eye (ICL) often comes up instead.

What is the difference between LASIK, PRK and SMILE?

All three are refractive surgery, meaning surgery that improves the eye's focusing power, and each one reshapes the cornea by removing a small amount of tissue. The same type of laser is used for LASIK and PRK; the main difference between them is how the surgeon exposes the stroma, the middle layer of the cornea.

	LASIK	PRK	SMILE
How the cornea is reshaped	Under a flap that is cut, folded back and then put back in place	At the surface, after the thin outer layer of cells (epithelium) is removed	By removing a small disc of tissue, cut inside the cornea, through a small incision
Flap	Yes	No	No
First days	Burning, itching or a feeling that something is in the eye, with hazy or blurry vision	Moderate pain for 1 to 2 days, some pain or discomfort for up to 3, and a bandage contact lens for 3 to 5 days if the surgeon uses one	Some discomfort or pain as the numbing wears off, and mild light sensitivity

The LASIK column follows the FDA's LASIK guide, the PRK column the FDA-approved booklet for one PRK laser system, and the SMILE column the booklet for the VisuMax laser used for SMILE.

LASIK vs PRK: which one suits your eyes?

That depends on your corneas and how you live. PRK's advantage is that no flap is created: the FDA-approved booklet for one PRK laser system says its benefits over LASIK may include removing the risk of a flap complication, including the flap dislocating after an injury, and that PRK may be preferable to LASIK for corneas that are normal but thin.

Lifestyle counts too. The FDA says you are probably not a good candidate for refractive surgery, PRK included, if you actively take part in contact sports where blows to the face and eyes are a normal occurrence. PRK does take one risk off the table, a flap knocked out of place, so tell the surgeon about your sports.

PRK's main drawback is a slower, sorer start. In the FDA-approved booklet for one PRK laser system, the eye may hurt moderately for 1 to 2 days once the numbing wears off, mild to moderate pain and discomfort can last up to 3 days, a bandage contact lens may protect the surface for 3 to 5 days, and vision takes longer to improve and stabilize than after LASIK. Corneal haze, a cloudiness of the cornea, may occur after PRK, and your doctor monitors you for side effects if you need steroid drops.

LASIK's trade-off is the flap itself. Some complications, such as the flap moving out of place (migration), inflammation or infection, may require another procedure. After LASIK, it can take up to 3 to 6 months for vision to stabilize.

SMILE vs LASIK: how do they differ?

SMILE (small incision lenticule extraction) reaches the tissue through a small incision instead of a flap, and its FDA approval covers nearsightedness, with or without astigmatism. The FDA-approved booklet for the VisuMax laser used for SMILE covers nearsightedness of -1.00 to -10.00 diopters, with or without up to -3.00 diopters of astigmatism and no more than -10.00 combined, in people 22 or older whose prescription changed by no more than 0.50 diopter in the year before surgery. Diopters are the units on a glasses prescription, and the minus sign marks nearsightedness. LASIK can also treat farsightedness.

The VisuMax booklet says vision should stabilize within a few weeks and warns never to rub or touch the treated eye. It doesn't compare that time with LASIK, so ask the surgeon what to expect for your eyes.

At our office, one mapping visit sorts LASIK, PRK and SMILE candidacy, and the surgeon confirms whether your prescription fits the SMILE window.

ICL vs LASIK: when does a lens implant make sense?

An ICL often comes up when a prescription is too high, or a cornea too thin, for laser surgery; see EVO ICL co-management. The implantable collamer lens corrects vision from inside the eye: a surgeon places it through a small incision in the cornea, behind the iris (the colored part of the eye) and in front of your natural lens.

The EVO and EVO+ Visian ICL is FDA-approved for adults 21 to 45. Its patient booklet says it corrects nearsightedness from -3.0 to -15.0 diopters and partially corrects it up to -20.0, and a toric version also treats astigmatism. LASIK, PRK and SMILE reshape the cornea, while an ICL adds a lens. The booklet says the lens can be removed at a future date, but that its lasting effect on the eye after removal isn't known and vision may not return to what it was before surgery.

The booklet's risks include a cataract risk that rises with each year the lens is in the eye, an early rise in eye pressure, and loss of endothelial cells, the cell layer lining the inside of the cornea. The lens isn't used during pregnancy or nursing, under age 21, or with moderate to severe glaucoma.

Who shouldn't have laser eye surgery?

LASIK isn't right for everyone, and NEI says you need a comprehensive dilated eye exam to find out whether it's right for you. The FDA lists these reasons you are probably not a good candidate for LASIK or other refractive surgery, or extra risks to discuss with your doctor:

You're under 18; no lasers are approved for LASIK in people under 18
Your glasses or contact lens prescription changed in the past year
You're pregnant or breastfeeding
You have a disease or take a medicine that may affect healing, such as an autoimmune disease or steroids
You've had herpes simplex or shingles involving the eye area, glaucoma, uveitis (inflammation inside the eye), keratoconus, or an eye injury or earlier eye surgery
Your corneas are too thin, your pupils are large, or you have dry eye, which LASIK tends to aggravate
You play contact sports

The PRK and SMILE booklets add their own lists. The FDA-approved booklet for one PRK laser system rules out PRK with that laser for significant dry eye, signs of keratoconus (a cone-shaped cornea) and recent herpes eye infections, and lists a past herpes simplex or herpes zoster infection of the eye as a warning. The SMILE booklet rules out the same three (severe dry eye, signs of keratoconus and a recent herpes infection of the eye), along with corneas too thin for the correction needed.

Dry eye gets treated first: a few weeks of targeted treatment stabilizes the tear film so the corneal measurements repeat.

What are the risks of laser eye surgery?

Common side effects of LASIK include dry eye, glare or halos around bright lights, double vision, blurry vision and light sensitivity. They usually go away after a few months; rarely, they're permanent. If dryness lingers, our dry eye after LASIK page covers what helps.

The FDA adds that some patients lose lines on the vision chart that glasses can't correct, some are under- or over-treated, and long-term data are not available.

One PRK laser's FDA-approved booklet warns that you may have dry eyes after PRK even if you didn't before, and the VisuMax SMILE booklet lists dry eye, halos, glare, starbursts and difficulty with night driving among possible symptoms, along with rare corneal risks such as scarring or a bulging cornea (ectasia).

Presbyopia, the age-related loss of close-up focus, still comes with age. LASIK can't fix it, and the VisuMax SMILE booklet says people around 40 or older may need reading glasses even if they didn't before.

Our yearly exams after surgery watch for rare late complications such as post-LASIK ectasia, a slow bulging of the cornea.

How we help you decide at Cohenmehr Optometry

We don't perform surgery. A trusted refractive surgeon does the procedure, and your care before and after it happens in our office.

The candidacy work-up maps the shape and thickness of your corneas, checks that your prescription is stable, and examines the eye's surface and tear film.

If a procedure fits, our eye doctors in Los Angeles refer you with complete records. If none does, we say so and go over the alternatives, from other procedures to specialty contact lenses.

After surgery, follow-up visits happen here on the surgeon's schedule: healing, pressure and vision checks, drop management, dry eye care during recovery, and your final glasses or contact lens prescription once the eye settles.

After any of these procedures, call your surgeon right away for severe pain or for vision that gets worse instead of better, or go to an emergency room when the surgeon's office is closed. If you suddenly lose vision in the eye that had surgery, even if it comes back, call your surgeon right away; if you can't reach the surgeon, call 911. Call 911 right away for sudden loss of vision in your other eye or both eyes, sudden double vision, or any change in vision with face drooping, arm weakness or trouble speaking.

Questions patients ask

How long before LASIK should you stop wearing contacts?

At least 2 to 4 weeks before your first evaluation, depending on the lens. The FDA advises stopping soft lenses 2 weeks before, toric soft or rigid gas permeable (RGP) lenses at least 3 weeks before, and hard lenses at least 4 weeks before. Contact lenses change the shape of your cornea for up to several weeks after you stop wearing them, and measuring too soon can lead to a poor surgical plan. Switch to glasses before your LASIK candidacy evaluation.

How long does PRK last?

The reshaping is meant to be permanent. The FDA-approved booklet for one PRK laser system calls the treatment a permanent operation to the cornea that cannot be reversed, and it lists partial loss of the effect over time (regression) as a possible risk. Your eyes keep aging after surgery, though: everyone gets presbyopia, the age-related loss of close-up focus.

Can you get PRK twice?

Sometimes, and the surgeon decides. The FDA-approved booklet for one PRK laser says you may need another laser treatment if the results aren't satisfactory, and that it isn't known whether repeating PRK on the same eye is safe and effective with that laser. The FDA's LASIK guidance adds that after a previous refractive surgery, more may not be recommended. Through PRK co-management, we track healing after PRK and coordinate an enhancement with your surgeon if one is ever needed.

How can you speed up PRK recovery?

Mostly by protecting the healing surface and following your aftercare exactly. The FDA-approved booklet for one PRK laser system says not to rub your eye until your doctor says it's safe, to use lubricants and eye medicines as directed, and to avoid swimming, hot tubs and spas for the first three weeks. We check the bandage lens and your drop schedule through the first week. If the eye gets worse instead of better, call your surgeon right away, or go to an emergency room when the surgeon's office is closed.

Sources

Written by

Dr. Kevin Cohenmehr, OD

Medical eye care: glaucoma, diabetic eye exams, macular degeneration and eye infections, plus vision therapy for children. A graduate of UCLA and SUNY College of Optometry.

About Dr. Kevin →

LASIK vs PRK vs SMILE: How the Three Laser Surgeries Compare