Debate: FS-LASIK or KLEx for Hyperopia?

Which is the better corneal refractive treatment for hyperopia up to 4.00 D, femtosecond laser-assisted in situ keratomileusis (FS-LASIK) or keratorefractive lenticule extraction (KLEx)? Two experts debated the question in a symposium at the ASCRS 2025 annual meeting in Los Angeles.

In this corner, FS-LASIK

Arguing for FS-LASIK, Michael Mimouni MD noted it is faster to heal, has a lower regression risk, is more comfortable, and has a quicker vision recovery time than KLEx. “When it comes to what patients care about, FS-LASIK is ahead in every category,” he said.

Focusing on SMILE, the first KLEx technique to reach the market, Dr Mimouni noted a 2022 study by Dr Dan Z Reinstein and colleagues found that in hyperopic patients, 83% achieved 20/20 uncorrected vision or better, with 81% within 0.50 D of target, and 93% within 1.00 D, with good predictability and safety—not terrible, but still slightly inferior to hyperopic LASIK, he said.¹

As far as the theoretical advantages of KLEx, a study comparing patients with FS-LASIK in one eye and SMILE in the other found they preferred LASIK.² Another study found that, when measured by decrease in corneal stiffness, biomechanics were in fact worse with SMILE than LASIK or PRK, with residual stromal bed thickness apparently the biggest factor.³

For dry eye, yet another study found that, though SMILE initially resulted in less corneal denervation, there was no difference at 12 months, and self-reported dry eye symptoms were similar, Dr Mimouni argued.⁴

Dr Mimouni even asked ChatGPT and got this response: “In the hands of equally skilled surgeons, I’d go with what’s tried, true, and time-tested: FS-LASIK.”

KLEx comes out swinging

Sri Ganesh MBBS countered that Dr Mimouni’s arguments about corneal biomechanics and denervation mainly cited studies of myopic procedures, and cherry-picked them at that. Acknowledging even his own experience with SMILE is limited, Dr Ganesh, who participated in a multicentre approval study for hyperopic SMILE, sees great promise in the procedure. “If you look at hyperopia, SMILE has not even opened its eyes. Let’s see how the new baby performs.”

An early study of femtosecond lenticule extraction (FLEx) in 40 eyes with hyperopia found 70% within 0.50 D of target 9 months after surgery, Dr Ganesh noted.⁵ Another early study found good centration and optical zones effectively larger than LASIK with hyperopic SMILE.⁶

In the multicentre approval trial involving 374 eyes of 199 patients with up to +6.00 D hyperopia, 5.00 D cylinder, and 7.00 spherical equivalent, 80% achieved 20/25 or better uncorrected vision and 100% 20/40 or better 12 months after treatment.

Predictability was also good, with 81% within 0.50 D of target and 93% within 1.00 D. Results varied by the magnitude of correction. Astigmatic correction was good as well, with 75% within 0.50 D of target and 93% within 1.00 D.

“Within 4.00 D, the results were excellent and stable,” Dr Ganesh said. However, corrections of more than 3.00 spherical equivalent showed increasing undercorrection, which may be due to healing factors. These results may be improved by modifying the nomogram, he added.

Safety was similarly encouraging, with 11% losing up to one line of vision, 1.3% losing up to two lines, and 10% gaining one line. The safety index rose from about 0.83 at one day after surgery to about 1.00 at 12 months, possibly reflecting the effects of healing over time, Dr Ganesh said. Stability was also good, though there was some regression even after 9 months, possibly due to late epithelial healing. However, this was less than typically seen with LASIK, possibly due to smaller optical zones, he added.

Overall, the results were better than in previous FLEx and SMILE studies, and refractive outcomes were marginally better than hyperopic LASIK with the MEL 90 (Zeiss), Dr Ganesh noted. Yet visual recovery was slower compared with FS-LASIK.

“The advantage is [KLEx] is more stable and there is less regression than with hyperopic LASIK,” though some issues remain, such as long treatment time and potential suction loss, Dr Ganesh said. However, the newer VISUMAX 800 laser should somewhat address these issues, as treatment times are expected to decrease from about 35 seconds to 12 seconds, making it an excellent option for hyperopia and hyperopic astigmatism, he concluded.

Michael Mimouni MD is associate professor at Technion-Israel Institute of Technology and director of the cornea unit at Rambam Health Care Campus, both in Haifa, Israel. michael@intername.co.il

Sri Ganesh MBBS, MS, DNB, DSC(Hon), FRCS(Gla), FWCRS is chairman and managing director of Nethradhama Hospitals in Bangalore, India. care@nethradhama.org

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2. Ma KK, Manche EE. J Cataract Refract Surg, 2023 Apr 1; 49(4): 348–353.

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6. J Refract Surg, 2017 Mar; 33(3) and 2017 Jun; 33(6).