Published in Refractive Surgery

$1 or Mystery Gift? SMILE Refractive Surgery Edition

Eyes On Eyecare Editorial Team

Eyes On Eyecare Editorial Team

This is editorially independent content supported by advertising from Carl Zeiss Meditec
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Discover what fellow optometrists know about small incision lenticule extraction (SMILE) refractive surgery with the game $1 or Mystery Gift.

$1 or Mystery Gift? SMILE Refractive Surgery Edition
Under the dazzling lights of Vision Expo East, the team at Eyes On Eyecare approached optometrists with a tantalizing offer: $1 or a Mystery Gift!
The mystery gifts were theirs for the taking under one condition: answer a question about SMILE refractive surgery.
While some optometrists may still be unfamiliar with SMILE, it is rapidly gaining popularity because of its predictability, excellent initial outcomes, and rapid recovery time.

How much did your colleagues know about SMILE when we put them on the spot?

Watch your optometry friends' full reactions on TikTok!

Find out who the SMILE pro is and who needs to up their game. New video drops every Friday!

Overview of SMILE refractive surgery

Small incision lenticule extraction—better known as SMILE in today’s eyecare circles—represents one of the most recently envisioned, unique, and minimally invasive forms of keratorefractive surgery.
In this bladeless procedure, the femtosecond laser is employed to create a small “pocket” in the anterior corneal stroma by making two disc-shaped ablative cuts, effectively forming a lenticule (i.e., a thin, lens-shaped layer) of corneal tissue inside the pocket (Figure 1). The laser also creates a small tunnel incision at the edge of the lenticule, which allows for surgical extraction of the disc in a minimally-invasive fashion.1
The end result is similar to laser-assisted in situ keratomileusis (LASIK), but without any flap-related complications and potentially with a much faster recovery time.2
Figure 1 is a graphical representation of SMILE from left to right: The femtosecond laser dissects the central cornea in two parallel planes that overlap at the periphery, creating a lenticule of corneal stroma between the incisions. This is removed by a small peripheral tunnel to the cap interface from the corneal surface, also created by the laser, and when the lenticule is removed, the cornea assumes a new shape, which corrects the refractive error.
SMILE surgery process
Figure 1: Courtesy of ZEISS.

Developments in SMILE refractive surgery

Interestingly, the concept behind SMILE was first described by Ito and associates nearly 30 years ago, using a picosecond laser to fashion intrastromal lenticules in human donor eyes.3
With the introduction of the VisuMax femtosecond laser (Carl Zeiss Meditec), however, this procedure moved from theory to reality. The first small clinical trial demonstrating the potential of femtosecond lenticule extraction in myopic patients was published in 2008.4 Subsequently, several larger, prospective trials to evaluate the safety and efficacy of SMILE were conducted.5,6,7

VisuMax 800 for SMILE refractive surgery

The VisuMax laser was initially approved by the US Food and Drug Administration (FDA) in 2016 for the treatment of spherical myopia.8 In January of 2024, the FDA granted approval for the VisuMax 800 with SMILE pro software, intended to surgically treat myopia with or without astigmatism.9
The VisuMax 800 is purported to have a four-fold faster laser repetition rate compared to the first-generation VisuMax (2MHz vs. 500kHz)—making it the most efficient design to date for performing SMILE.
In head-to-head clinical comparisons, SMILE has generally been found to have early post-operative outcomes similar to LASIK and superior to photorefractive keratectomy (PRK) in terms of visual outcome and post-surgical discomfort.10 Some studies suggest that SMILE offers a shorter recovery of post-operative dry eye and glare as compared to LASIK.10,11
Another study demonstrated marked improvement in corrected distance acuity along with excellent predictability for both SMILE and wavefront-guided LASIK; however, the latter resulted in faster visual recovery, better low-contrast visual acuity, and greater gains in uncorrected visual acuity.12
The FDA has approved SMILE for the treatment of up to 10.00 diopters of myopia and 0.75 to 3.00 diopters of astigmatism. At this time, however, the procedure is not approved for treating hyperopia.

Some advantages of SMILE may include:

  • A small incision, with little-to-no propensity for flap complications.
  • Rapid recovery time that is comparable to LASIK and superior to surface ablation.
  • SMILE is favorable toward the preservation of corneal nerves, reducing the likelihood of secondary dry eye disease (DED) or neurotrophic keratopathy.

Conclusion

While SMILE has yet to overtake LASIK as the treatment of choice for the majority of patients, it nonetheless has some extremely appealing qualities that make for a highly persuasive argument.
The most obvious reasons to favor SMILE over surface ablation procedures and even LASIK are the preservation of corneal nerves (i.e., less risk of post-operative DED) and the minimization of post-operative discomfort and visual rehabilitation.
With SMILE being performed on over 8 million eyes worldwide, it behooves the ECP to understand the unique advantages of this refractive surgery procedure and identify patients who may be excellent candidates for this increasingly popular technique.
  1. Moshirfar M, McCaughey MV, Reinstein DZ, et al. Small-incision lenticule extraction. J Cataract Refract Surg. 2015;41(3):652-665. doi:10.1016/j.jcrs.2015.02.006.
  2. Dong Z, Zhou X, Wu J, et al. Small incision lenticule extraction (SMILE) and femtosecond laser LASIK: comparison of corneal wound healing and inflammation. Br J Ophthalmol. 2014;98(2):263-269. doi: 10.1136/bjophthalmol-2013-303415.
  3. Ito M, Arai H, Fukumoto T, et al. INTACS before or after laser in situ keratomileusis: correction of thin corneas with moderately high myopia. J Refract Surg. 2004;20(6):818-822. doi:10.3928/1081-597X-20041101-10.
  4. Sekundo W, Kunert K, Russmann C, et al. First efficacy and safety study of femtosecond lenticule extraction for the correction of myopia: six-month results. J Cataract Refract Surg. 2008;34(9):1513-1520. doi:10.1016/j.jcrs.2008.05.033.
  5. Sekundo W, Kunert KS, Blum M. Small incision corneal refractive surgery using the small incision lenticule extraction (SMILE) procedure for the correction of myopia and myopic astigmatism: results of a 6 month prospective study. Br J Ophthalmol. 2011;95(3):335-339. doi:10.1136/bjo.2009.174284.
  6. Shah R, Shah S, Sengupta S. Results of small incision lenticule extraction: All-in-one femtosecond laser refractive surgery. J Cataract Refract Surg. 2011;37(1):127-137. doi:10.1016/j.jcrs.2010.07.033.
  7. Hjortdal JØ, Vestergaard AH, Ivarsen A, et al. Predictors for the outcome of small-incision lenticule extraction for Myopia. J Refract Surg. 2012;28(12):865-871. doi:10.3928/1081597X-20121115-01.
  8. US Food and Drug Administration. FDA approves VisuMax Femtosecond Laser to surgically treat nearsightedness. US Food and Drug Administration (FDA). Published September 13, 2016. Accessed January 23, 2024. https://www.fda.gov/news-events/press-announcements/fda-approves-visumax-femtosecond-laser-surgically-treat-nearsightedness.
  9. Delaney-Gesing A. FDA approves ZEISS's VISUMAX 800 with new SMILE pro software. Glance by Eyes on Eyecare. Published January 11, 2024. Accessed January 23, 2024.https://glance.eyesoneyecare.com/stories/2024-01-11/fda-approves-zeiss-s-visumax-800-with-new-smile-pro-software/.
  10. 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. doi:10.1097/j.jcrs.0000000000000203.
  11. Han T, Xu Y, Han X, et al. Quality of life impact of refractive correction (QIRC) results three years after SMILE and FS-LASIK. Health Qual Life Outcomes. 2020;18(1):107. doi:10.1186/s12955-020-01362-8.
  12. Chiang B, Valerio GS, Manche EE. Prospective, Randomized Contralateral Eye Comparison of Wavefront-Guided Laser In Situ Keratomileusis and Small Incision Lenticule Extraction Refractive Surgeries. Am J Ophthalmol. 2022;237:211-220. doi:10.1016/j.ajo.2021.11.013.
Eyes On Eyecare Editorial Team
About Eyes On Eyecare Editorial Team

Led by Editor-in-Chief Eleanor Gold, PhD, Eyes On Eyecare is a digital publication that provides clinical and career education to the young generation of optometrists and ophthalmologists. We work with eyecare professionals to create compelling, educational content available for free to all those in the eyecare industry. To learn more about our team, values, and other projects, visit our About page.

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