KLEx Comes of Age

Where KLEx Fits Beside LASIK

By Luke Rebenitsch, MD

I was an early adopter of keratorefractive lenticule extraction (KLEx). I attended a course led by Dan Z. Reinstein, MD, MA(Cantab), FRCSC, DABO, FRCOphth, FEBO, PGDip CRS, CertLRS, in London, and I have been interested in the procedure ever since. My enthusiasm, however, has never led me to write an obituary for LASIK.

LASIK is one of the most versatile procedures refractive surgeons have. It can treat hyperopia, myopia, and astigmatism; it can address small and large refractive errors; and it remains an excellent means for laser enhancements. With the increase in refractive lens exchange (RLE) across the globe, LASIK clearly retains a place in surgeons' armamentarium. A more interesting question is where KLEx sits alongside it.

Why I Recommend KLEx First

What I like about KLEx is that it offers many of the benefits of LASIK while potentially decreasing the intensity of postoperative dry eye symptoms and the risk of diffuse lamellar keratitis. In my experience, KLEx also provides an expanded effective optical zone and improved refractive stability in appropriate candidates. I first learned about these potential advantages during the Reinstein course and have since observed them in clinical practice. Because it disrupts the anterior cornea less than LASIK, KLEx may also preserve more options for the future. For example, I would much rather perform RLE after KLEx, with the option of a thin-flap LASIK touch-up if needed, than perform RLE after LASIK and have to consider lifting a flap.

Patient Demand Is Changing

Procedural demand matters. Negative attention around LASIK is pervasive on social media, and a growing group of patients would never choose to undergo this procedure. Those patients are looking for options. In practice, many of them ask specifically about alternatives to LASIK, such as a flapless procedure, implantation of the EVO ICL (STAAR Surgical), and RLE.

The patients who ask me about KLEx have done their research. They are interested in vision correction, but they are apprehensive about LASIK. Denigrating any procedure is neither productive for the industry nor useful for patients. For those seeking what they perceive as a lower-risk option, however, KLEx can be an appealing option if they are candidates for the procedure.

Selecting the Right Procedure

In my practice, PRK is reserved for patients who do not qualify for LASIK or KLEx, typically because their corneas are abnormal or thin. If a patient is not a good candidate for corneal laser vision correction, I usually recommend the EVO ICL.

Candidacy Criteria

My screening criteria for LASIK and KLEx are similar. I use the same residual stromal bed requirement and the same 40% tissue altered threshold. With the treatment parameters currently available in the United States, however, KLEx may remove slightly more tissue than LASIK in some eyes because we are limited to a 120-µm cap and a 15-µm nonrefractive aspect of the lenticule.¹ The following statement may be somewhat controversial, but I strongly believe that almost every patient should receive a 6.5-mm optical zone with KLEx.

Refractive Range

In general, I reserve LASIK and KLEx for patients with -1.00 to -7.00 D of myopia and up to 3.00 D of cylinder. I discuss the EVO ICL with any patient who has at least -6.00 D of myopia and strongly prefer this treatment strategy for anyone with greater than -7.00 D of myopia. For patients in their 40s and beyond and for presbyopic patients, RLE may also enter the discussion.

Biomechanical Considerations

Studies have disagreed on how much biomechanical strength is preserved with KLEx versus LASIK.² Recent KLEx guidance has recommended maintaining a residual stromal thickness of 280 µm or more, with an absolute lower limit of 250 µm.³

When a patient qualifies for both procedures, I favor KLEx over LASIK because the former offers a possible biomechanical advantage, a lower risk of postoperative dry eye symptoms, greater patient comfort, fewer flap- or cap-related complications, and fewer early postoperative restrictions. LASIK retains clear advantages for low, hyperopic, and mixed corrections.

Visual Recovery in 2026

The speed of postoperative visual recovery deserves honest consideration. When the VisuMax 500 (Carl Zeiss Meditec) first became available, energy parameters were not well established, and, as with many excimer laser platforms, nomogram adjustments were required. Until those nomograms were developed, outcomes were less predictable.

In 2026, energy optimization has improved, and anecdotal reports from surgeons using the VisuMax 800 (Carl Zeiss Meditec) suggest faster early visual recovery than with the VisuMax 500. Patients' visual recovery is probably slightly faster with LASIK on postoperative days 1 and 2, especially when the amount of correction is small, but by 1 month, the results with both procedures are similar.⁴ Clinically, I would not call the difference in visual recovery meaningful.

The learning curve is the caveat. KLEx is more challenging to perform than LASIK, and a surgeon's early KLEx patients may experience a slower visual recovery due to surgical technique alone. That should improve over time.

Managing KLEx's Weak Points

Suction Loss

Suction breaks can happen with either VisuMax platform, although they are less likely with the VisuMax 800 because the procedure is much faster. Preoperatively, I counsel patients that I may be unable to complete KLEx because of a suction break and that LASIK may be the best option at that point. Suction loss during KLEx is a rare occurrence.

Enhancements

Enhancing a KLEx result is relatively straightforward, and there are multiple techniques. My preferred method is thin-flap LASIK. I typically program a 95-µm flap, although some surgeons program 90 µm. It is relatively straightforward to create the flap and perform the ablation. For patients who do not want a flap, PRK is an option. Some surgeons create a flap using the same plane created for the lenticule with a cap-to-flap technique. Outside the United States, the Circle software (Carl Zeiss Meditec) has also been used.

My enhancement rate is lower with KLEx than LASIK.

Advice for Surgeons Adopting KLEx

Surgeons interested in offering KLEx must recognize that the procedure is not the same as LASIK. KLEx is more challenging to perform, and mastering the technique is important.

That said, surgeons who want to perform KLEx should know how to perform LASIK at a high level because many of those principles apply to KLEx. I recommend consulting an experienced KLEx surgeon or industry clinical specialist who can provide step-by-step guidance.

Technique, nomogram development, and energy settings are critical to performing KLEx at a high level.

Platform selection matters as well. Although the treatment parameters are similar with both laser systems, the greater speed of the VisuMax 800 may decrease inflammation, improve lenticule smoothness, and accelerate visual recovery compared with the VisuMax 500, at least according to early anecdotal reports. In my experience, the dissection is easier, and visual recovery is faster with the VisuMax 800. I recommend that a surgeon starting to perform KLEx use the newer platform when feasible.

A Broader Refractive Toolkit

The demand for refractive surgery has not diminished, but the demand for specific procedures has changed. I expect LASIK volume to continue declining with growth in alternatives such as KLEx, phakic IOLs, and RLE. By 2030, I would guess the market may reach a steady state of roughly 50% to 60% LASIK, with the balance distributed among the alternatives.

1. Carl Zeiss Meditec AG. VisuMax Femtosecond Laser: Small Incision Lenticule Extraction (SMILE) Procedure for the Correction of Myopia [professional use information]. Carl Zeiss Meditec AG; 2016.
2. Reinstein DZ, Archer TJ, Gobbe M. Small incision lenticule extraction (SMILE) history, fundamentals of a new refractive surgery technique and clinical outcomes. Eye Vis (Lond). 2014;1:3. doi:10.1186/s40662-014-0003-1
3. Wang Y, Xie L, Yao K, et al. Evidence-based guidelines for keratorefractive lenticule extraction surgery. Ophthalmology. 2025;132(4):397-419. doi:10.1016/j.ophtha.2024.11.016
4. Rebenitsch RL. SMILE vs LASIK: Which offers better early visual recovery? American Academy of Ophthalmology. October 16, 2018. Accessed July 27, 2026. https://www.aao.org/education/editors-choice/smile-vs-lasik-which-offers-better-early-visual-re

KLEx Versus LASIK in 2026

By Dan Z. Reinstein, MD, MA(Cantab), FRCSC, DABO, FRCOphth, FEBO, PGDip CRS, CertLRS

Keratorefractive lenticule extraction (KLEx) entered the refractive surgery conversation in 2011 with ReLEx SMILE, performed with the VisuMax femtosecond laser (Carl Zeiss Meditec).¹ At the time, the debate was framed largely as SMILE versus LASIK. LASIK had decades of clinical development behind it, with excellent outcomes, rapid recovery, broad indications, established enhancement pathways, and flexible excimer laser ablation profiles. SMILE was new, technically unfamiliar, more dependent on manual lenticule dissection, and initially more limited in its indications, customization options, enhancement pathways, and collective surgical experience. Surgeons and companies with established LASIK platforms could reasonably ask why a different procedure with fewer customization options and a more complex enhancement pathway should be adopted.

Fifteen years later, that question feels dated. SMILE and SMILE pro have now been performed on approximately 14 million eyes worldwide and are supported by more than 1,200 peer-reviewed publications.¹ SMILE had no direct commercial counterpart for nearly a decade. Only from 2020 onward did competing KLEx platforms begin to enter the field, including SmartSight (Schwind eye-tech-solutions), CLEAR (Ziemer Ophthalmic Systems), and SILK (Johnson & Johnson Vision).^2-4 Additional systems are in development.

The pendulum is shifting, but not because KLEx is replacing LASIK. It is shifting because lenticule extraction has become an established and expanding part of the refractive toolbox. SMILE provided the procedural experience, evidence base, technological iteration, and surgical teaching that established modern KLEx as a clinical category. The subsequent arrival of competing platforms reflects the maturation of the category established by SMILE rather than its creation and gives surgeons additional options to consider alongside LASIK and other refractive procedures.

As the category expands, the overwhelming majority of KLEx procedural experience, peer-reviewed evidence, technological iteration, and surgical teaching derives from SMILE and SMILE pro. Newer platforms do not yet have the same depth of procedural experience, publication history, technological iteration, or surgical maturity. Sharing the same procedural concept should not be mistaken for equivalence of evidence, iteration, clinical experience, or surgical maturity. Individual newer systems should therefore be evaluated according to the depth of their own supporting evidence and clinical experience.

Keeping the Conversation Clinical

Where LASIK Leads

The next phase of the discussion must be clinical rather than commercial. KLEx is not automatically superior because it is flapless or because more companies have entered the field, and LASIK is not obsolete because lenticule extraction has matured. LASIK remains an outstanding procedure. It is still more versatile for topography-guided procedures as well as for the treatment of many patients with hyperopia, mixed astigmatism, presbyopia, and complex pathology.^5-7 LASIK offers direct access to the stromal bed, rapid postoperative recovery, and a familiar enhancement pathway. When the optical correction depends primarily on a customized excimer laser ablation profile, LASIK is often the procedure of choice.

Where KLEx Adds Value

In appropriately selected myopic patients, particularly those with moderate to high myopia, intrastromal lenticule extraction avoids some sources of variability inherent to excimer laser ablation, including stromal bed dehydration and environmental influences during tissue removal.⁸ SMILE is often described as preserving corneal biomechanical strength better than LASIK, but this advantage should not be interpreted in isolation. LASIK has a low ectasia rate and strong long-term stability in appropriately selected eyes, and SMILE remains contraindicated in eyes with forme fruste keratoconus.⁹

A more clinically relevant optical advantage of SMILE is that larger functional optical zones can be achieved in myopic corrections, resulting in less induction of spherical aberration.^10,11 By preserving more of the anterior stromal architecture, SMILE also causes less disruption to the corneal nerves, which may allow faster recovery of corneal sensitivity and minimize early dry eye symptoms.¹² These advantages are realized only when SMILE is used for the appropriate indication and performed by a surgeon who can manage both routine and nonroutine lenticule extraction.

Flapless Does Not Mean Risk-Free

The appeal of flapless surgery to patients is real, but surgeons must provide clear, honest education. Avoiding the creation of a flap may be practically relevant to combat-sport athletes and patients with unusual occupational trauma risk. Patients, moreover, understandably like the idea of a smaller incision. LASIK, however, is already safe when performed properly, and surgeons should not frighten patients away from LASIK to sell KLEx.

An honest conversation about the two procedures explains that they have different risk profiles. LASIK flap–related problems cannot occur with KLEx, but there are intraoperative situations with KLEx that do not exist with LASIK. These include dissection of the wrong plane, difficult lenticule separation, lenticule remnants, cap-related events, and interface management decisions.^13,14

Surgical Maturity Matters

Technology Has Improved

What has changed most since the early days of SMILE is not only technology but also knowledge. With SMILE Pro, computer-assisted docking, centration, and cyclotorsion control have reduced the need for manual adjustments at the start of the procedure. Faster lenticule cutting has made suction loss less frequent. With current SMILE Pro treatment times, lenticule creation can be completed in less than 10 seconds, reducing the opportunity for Bell phenomenon, movement, or loss of fixation.¹⁵ A better understanding of energy settings and spot spacing has improved patients' visual recovery on postoperative day 1, often bringing early recovery closer to what surgeons expect from LASIK. Cylinder nomograms have improved. Standard operating procedures for routine extraction have become teachable, and so have strategies for nonroutine lenticule extraction. These changes matter because KLEx is both a laser procedure and a manual microsurgical procedure.

Competence Remains the Barrier

The capital cost of laser systems for KLEx remains significant, but a greater barrier to the adoption of this procedure is surgeon competence. Buying a KLEx platform does not create a lenticule surgeon. They must understand laser-tissue interaction, bubble patterns, interface geometry, the feel of dissection, instrument design, and when an extraction is not routine. A lenticule that does not come out with the first maneuver is not necessarily a complication; it is a surgical situation requiring a plan.

Enhancements Reflect Category Maturity

Early objections to SMILE often focused on retreatment. Before the development of Circle software (Carl Zeiss Meditec) to convert the cap into a flap, surface ablation was commonly recommended, while subcap lenticule extraction was also described as an alternative enhancement technique. Each has a role, but in my view, the optimal enhancement method after SMILE, when anatomy permits, is thin-flap LASIK. With epithelial and cap thickness mapping, a superficial LASIK flap can be planned with high confidence that it will remain anterior to the original SMILE interface while accounting for postoperative epithelial thickening after myopic correction.¹⁶ Done properly, this approach can offer the advantages of LASIK as an enhancement procedure while preserving the benefits of primary KLEx.

The Mark of a Mature Surgeon

The field is moving from procedural tribalism to indication-based refractive surgery. To my mind, the contemporary refractive surgeon should not be a LASIK surgeon who occasionally performs KLEx or a KLEx surgeon who dismisses LASIK as old technology. A mature refractive surgeon should understand both procedures, offer both, manage the complications of both, and select between them without marketing bias. SMILE has established KLEx as a core part of the refractive toolbox for appropriately selected myopic patients, particularly when its optical, ocular surface, or flap-related advantages are clinically relevant. The future is not flap versus flapless. It is knowing when each procedure is the right operation.

1. ZEISS Medical Technology. SMILE 10 million eyes. ZEISS. Accessed June 30, 2026. https://www.zeiss.com/meditec/en/c/opt/smile/10-million-eyes-with-zeiss-smile-and-smile-pro.html
2. SCHWIND eye-tech-solutions. CE approval for SCHWIND ATOS and SmartSight. SCHWIND eye-tech-solutions. Published July 10, 2020. Accessed June 30, 2026. https://www.eye-tech-solutions.com/en/infocenter/press/ce-approval-for-schwind-atos-and-smartsight
3. Ziemer Ophthalmic Systems. The Ziemer lenticule application CLEAR is now CE marked. Ziemer. Accessed June 30, 2026. https://www.ziemergroup.com/en/news/7/the-ziemer-lenticule-application-clear-is-now-ce-marked/
4. Johnson & Johnson Vision. Johnson & Johnson Vision receives CE Mark approval for new corneal refractive technology, the ELITA Femtosecond Laser System. Johnson & Johnson Vision. Published March 1, 2023. Accessed June 30, 2026. https://www.jjvision.com/en-us/news-media-center/releases/elita-laser-ce-approval
5. Reinstein DZ, Archer TJ, Gobbe M. Outcomes of presbyopic micro-monovision LASIK for myopia, hyperopia and emmetropia. Presented at: XXVI Congress of the European Society of Cataract and Refractive Surgeons; September 13-17, 2008; Berlin, Germany.
6. Reinstein DZ, Carp GI, Archer TJ, Day AC, Vida RS. Outcomes for hyperopic LASIK with the MEL 90 excimer laser. J Refract Surg. 2018;34(12):799-808. doi:10.3928/1081597X-20181019-01
7. Reinstein DZ, Archer TJ, Gobbe M. Combined corneal topography and corneal wavefront data in the treatment of corneal irregularity and refractive error in LASIK or PRK using the Carl Zeiss Meditec MEL 80 and CRS-Master. J Refract Surg. 2009;25(6):503-515. doi:10.3928/1081597X-20090512-04
8. Reinstein DZ, Archer TJ, Vida RS, et al. Small incision lenticule extraction (SMILE) for the correction of high myopia with astigmatism. J Refract Surg. 2022;38(5):262-271. doi:10.3928/1081597X-20220314-01
9. Randleman JB, Dawson DG, Grossniklaus HE, McCarey BE, Edelhauser HF. Depth-dependent cohesive tensile strength in human donor corneas: implications for refractive surgery. J Refract Surg. 2008;24(1):S85-S89. doi:10.3928/1081597X-20080101-15
10. Ganesh S, Gupta R. Comparison of visual and refractive outcomes following femtosecond laser-assisted LASIK with SMILE in patients with myopia or myopic astigmatism. J Refract Surg. 2014;30(9):590-596. doi:10.3928/1081597X-20140814-02
11. Lin F, Xu Y, Yang Y. Comparison of the visual results after SMILE and femtosecond laser-assisted LASIK for myopia. J Refract Surg. 2014;30(4):248-254. doi:10.3928/1081597X-20140320-03
12. Reinstein DZ, Archer TJ, Gobbe M, Bartoli E. Corneal sensitivity after small-incision lenticule extraction and laser in situ keratomileusis. J Cataract Refract Surg. 2015;41(8):1580-1587. doi:10.1016/j.jcrs.2014.12.055
13. Reinstein DZ, Vida RS, Archer TJ, Carp GI. Aborted small-incision lenticule extraction resulting from false plane creation and strategy for subsequent removal based on corneal layered pachymetry imaging. J Cataract Refract Surg. 2019;45(6):872-877. doi:10.1016/j.jcrs.2019.02.036
14. Ganesh S, Brar S, Lazaridis A. Management and outcomes of retained lenticules and lenticule fragments removal after failed primary SMILE: a case series. J Refract Surg. 2017;33(12):848-853. doi:10.3928/1081597X-20171004-01
15. Reinstein DZ, Archer TJ, Vida RS, Carp GI. Suction stability management in small incision lenticule extraction: incidence and outcomes of suction loss in 4000 consecutive procedures. Acta Ophthalmol. 2020;98(1):e72-e80. doi:10.1111/aos.14215
16. Reinstein DZ, Carp GI, Archer TJ, Vida RS. Outcomes of re-treatment by LASIK after SMILE. J Refract Surg. 2018;34(9):578-588. doi:10.3928/1081597X-20180717-02