SMILE vs LASIK

28 Feb SMILE vs LASIK

SMILE and LASIK are both laser refractive procedures that can treat Myopia and Astigmatism. As a result, patients need to choose SMILE vs LASIK when they correct their eyes. The external incision in SMILE is smaller than the incision for LASIK which results in advantages for some patients. How do you chose between the two?

SMILE vs LASIK: Strength of Your eye:

The first consideration is the strength of your eye. Most of the screening tests done before you have your laser eye surgery are to determine if you have enough corneal strength to undergo laser eye surgery.  If you are told you are not a candidate, it is usually because your surgeon fears that you do not have enough strength to handle the amount of correction you will need.  This could mean you have a big prescription, a thin cornea, or evidence of a weaker than normal corneal.  The goal is to end up with a cornea that can hold its strength and shape for the rest of your long and wonderful life. 

LASIK and SMILE both remove a thin lenticule of tissue from the middle part of the cornea.  This part of the corneal is not that important in providing strength to the cornea. As a result, there is a minimal and inconsequential weakening in appropriate candidates. The front part of the cornea is the strongest part of the cornea. 

Creating the LASIK flap cuts across the stronger anterior cornea for 320 degrees whereas SMILE only cuts 60 degrees of this tougher anterior cornea.  As a result, the cornea is stronger after SMILE vs LASIK. Appropriate candidates for LASIK have more than enough strength reserve for this procedure, but all other factors being equal, the great biomechanical strength left by SMILE is compelling.^1,2 

Extreme Sports & Refractive Surgery

The LASIK flap is more susceptible to extreme trauma.  SMILE does not have a flap, so could be preferred for patients that engage in extreme sports, martial arts, or for first responders who put their eyes in harm’s way. 

SMILE vs LASIK: Dry Eye and Refractive Surgery

Most patients sense an increase in dry eye symptoms after laser eye surgery for the first 3-6 months but then return to whatever was their preop baseline for dryness after they heal.  Part of the reason this happens is because we disturb the nerves that sense dryness in the cornea and they need that amount of time to heal.  Those nerves are most concentrated in the anterior part of the cornea and since LASIK transects those nerves for 320 degrees and SMILE for only 60 degrees we tend to see less dry eye after SMILE.^3,4 

Size of Your prescription:

For small prescriptions, LASIK is often better than SMILE.  This is because in SMILE the lenticule needs to be strong enough to be grasped for removal through the small incision.  In a small prescription, the lenticule may be too thin for removal with SMILE so LASIK is preferred. 

Can the SMILE Procedure Correct Astigmatism?

Astigmatism means you eye is shaped more like an egg than a ball.  This make images out of focus.  Fortunately, refractive procedures like SMILE and LASIK treat astigmatism by returning your cornea to a more round shape so it can create a clearer focus.  Smile is FDA approved to treat up to 3 diopters of astigmatism while LASIK is FD approved to treat up to 5 diopters of astigmatism.  Patients which astigmatism greater than 3 diopters are  better served by LASIK.

Hyperopia (Far-Sightedness)

Around 10% of the population have hyperopia. LASIK can treat hyperopia but SMILE is not FDA approved to treat hyperopia.

SMILE LASIK

The accuracy results of LASIK and SMILE are equivalent for patients with normal prescriptions.⁵  LASIK has a greater ability to be customized for patients with non-standard prescriptions.  Patients with non-standard shapes to their corneas or overall visual system may be better served by “topo guided” or “wavefront-guided” LASIK treatments than SMILE. 

SMILE PROCEDURE Enhancements

Around 2-6% of patients need to have an enhancement procedure after LASIK or SMILE depending on their prescription.  LASIK can generally be enhanced with LASIK or PRK.  SMILE can also generally be enhanced with LASIK or PRK, but not SMILE. 

How do I Decide Between the SMILE vs LASIK?

The best way to decide between various laser vision correction options is to begin by studying information such as that listed above and then to consult with your optometrist to determine which surgeon in your region they recommend based on their results and how they care for their patients.  Then set up a consultation with the recommended ophthalmologist and seek their opinion.  They will be able to speak to the specific nature of your prescription and lifestyle needs and make a recommendation.  Ideally, the surgeon you consult would have both SMILE and LASIK lasers to help remove any potential for bias and bring experience to their recommendations. 

Gary Foster, MD is a SMILE procedure and LASIK surgeon in Northern Colorado and the medical director of The Eye and Laser Center of Northern Colorado, P.C.

1. Wu D, Wang Y, Zhang L, Wei S, Tang X. Corneal biomechanical effects: small-incision lenticule extraction versus femtosecond laser-assisted laser in situ keratomileusis. J Cataract Refract Surg. 2014;40(6):954-962.
2. Seven I, Vahdati A, Pedersen IB, et al. Contralateral eye comparison of SMILE and flap-based corneal refractive surgery: computational analysis of biomechanical impact. J Refract Surg. 2017;33:7:444-453. 
3. Denoyer A, Landman E, Trinh L, Faure JF, Auclin F, Baudouin C. Dry eye disease after refractive surgery: comparative outcomes of small incision lenticule extraction versus LASIK. Ophthalmology. 2015;122(4):669-676.
4. Cai WT, Liu QY, Ren CD, et al. Dry eye and corneal sensitivity after small incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis: a meta-analysis. Int J Ophthalmol. 2017;10(4):632-638.
5. Sia RK, Ryan DS, Beydoun H, et al. Visual outcomes after SMILE from the first-year experience at a U.S. military refractive surgery center and comparison with PRK and LASIK outcomes. J Cataract Refract Surg. 2020;46(7):995-1002.