SMILE Pro laser eye surgery: who is it for, and who is it not for?

Most people researching laser eye surgery notice the same thing: clinic pages all look alike. SMILE Pro is a good method, but it is not a method for everyone. To some of the eyes I assess I say "this method is not for you"; knowing the reasoning behind that sentence will serve you better than reading praise of the method.

I wrote this page so that you can ask the same questions whichever doctor you see, in Ankara or in any other city. You will not find a promise of results here; I describe the risks and the limits of the method with the same openness.

The short answer

SMILE Pro is a laser method that corrects myopia (short-sightedness) and astigmatism through a small incision, without creating a flap in the cornea. Whether you are suitable is determined by your cornea more than by your prescription: is your corneal topography (the map of the cornea) regular, is your cornea thick enough, will enough tissue be left behind after the procedure. For each of the numbers below, I give the source in the relevant section.

You may be suitable:

• If you are between 18 and 45 years old (the range I apply in my practice; if you accept reading glasses, I do not apply an upper limit) and your prescription has not changed for at least 1 year
• If your myopia is between −1.00 and −10.00 D; and, if you have astigmatism, it is up to −5.00 D (for astigmatism, the limit I apply in my practice; the limit in the US registration is −3.00 D)[1]
• In hyperopia (long-sightedness): if the sum of the sphere and cylinder values is at most 5 D (the limit I apply in my practice; the US approval record does not cover hyperopia)
• If your corneal topography is regular and there is no suspicion of keratoconus
• If your corneal thickness leaves a safe residual bed after the tissue required by your prescription has been removed

You are not suitable, or I postpone:

• If corneal topography shows keratoconus or a suspicion of it
• If your cornea is thin or the tissue that would be left behind is insufficient
• If your prescription is still changing or is outside the range
• If you have marked dry eye or active ocular surface disease
• If you are pregnant or breastfeeding

What is SMILE Pro?

Removing a lenticule through a small incision, without creating a flap

There are three ways to correct a prescription with a laser. In PRK, the surface of the cornea is reshaped. In LASIK, a thin flap is lifted first, the tissue beneath it is reshaped, and the flap is laid back in place. In SMILE, the laser separates a thin, lens-shaped piece of tissue (the lenticule) inside the cornea; I take this piece out through a small incision. No flap is lifted, and most of the surface is left untouched.

How it differs from classic SMILE, and how it does not

SMILE Pro is the version of the same method performed with the new-generation laser (VisuMax 800). There are two concrete differences. The first is speed: in a comparative study, the time taken to create the lenticule was measured as 9.47 ± 0.88 seconds with the new generation and 27.43 ± 2.26 seconds with the previous generation.[2] The time your eye has to stay still under suction becomes shorter. The second is alignment: the device helps to centre the treatment on the eye and to compensate for the slight rotation of the eye around its own axis when you lie down.[3]

The honest answer to "So will I see better?" is more measured. In a meta-analysis that pooled nine studies (1,672 eyes) comparing the two generations, no statistically significant difference was found in vision of 20/20 or better, in safety, or in higher-order aberrations (fine optical imperfections). The only significant difference reported in its abstract is this: achieving the astigmatism axis within ±5° favoured the new generation (risk ratio 1.157). The authors also note that none of the included studies was randomised and that the risk of bias was judged "serious" in most of them.[3] In a prospective comparison of 140 eyes, too, no difference was found between visual and refractive outcomes at 6 months.[4]

Who is it suitable for?

Prescription range

For myopia, the limit I apply in my practice is the same as the official registration: up to −10.00 D. For astigmatism I depart from it, and I state the difference openly: the limit in the US registration is −3.00 D; I treat up to −5.00 D. This is above the official registration; it is my own clinical practice. Astigmatism above 3.00 D was among the factors that increased the risk of enhancement in one study;[15] the details are in the risks section. The values in the US Food and Drug Administration (FDA) registration are as follows: myopia −1.00 to −10.00 D, astigmatism −0.75 to −3.00 D, and the spherical equivalent (the combination of the two) not exceeding 10.00 D in magnitude.[1] The same range appears in the US device record of the new-generation device.[5]

Being within the range is not enough on its own. A high prescription means a thicker lenticule, and that means more tissue removed from the cornea. A −9.00 D eye may be within the range on paper, but if its cornea is thin I will not use this method in that eye.

Age and stability of the prescription

The age range I apply in my practice is 18 to 45. The lower limit in the FDA registration is higher: 22 years and over.[1] I am not hiding the difference between the two numbers. The reason for my upper limit of 45 is that near vision starts to decline around this age (presbyopia); if you accept wearing reading glasses, I do not apply an upper age limit. At any age I want the prescription to have been stable for at least 1 year (a condition I apply in my practice). The FDA registration defines this as "a change of at most 0.50 D in sphere and cylinder over the past year".[1] This is why bringing your old spectacle prescriptions is useful.

Corneal thickness and the tissue left after the procedure

There are three thresholds I apply in my practice. Corneal thickness at the thinnest point of at least 480 µm (microns). A residual stromal bed of at least 270 µm left underneath once the lenticule has been removed. A percent tissue altered (PTA: the ratio of the overlying tissue plus the removed tissue to the total thickness) below 40%.

Their counterparts in the literature are as follows. The basis for PTA is a study of eyes that developed ectasia (a gradual forward bulging of the cornea) after LASIK: in 97% of the eyes that developed ectasia despite normal topography, PTA was 40 or above.[6] For the residual bed, the limit traditionally used in LASIK screening is 250 µm;[7] my threshold is above that, in other words more cautious. As for 480 µm, it is my own clinical rule; there is no single publication I can point to for this number, and I do not present it as if there were. Let me add this as well: both of these studies were carried out in LASIK eyes; I use the same limits in SMILE Pro as a margin of caution.

These numbers do not decide anything on their own; I look at all of them together with the topography.

The situation in hyperopia

I also perform SMILE Pro for hyperopia; the upper limit I apply in my practice is a sum of the sphere and cylinder values of at most 5 D (not the spherical equivalent, but the sum of the two values). Here I need to state openly the difference between me and the official registration: the US registration I mentioned above covers only myopia (with or without astigmatism); it does not cover hyperopia.[1, 5]

I do not perform PRK for hyperopia; in this group my options are LASIK and SMILE Pro. In my experience so far, SMILE Pro is quite effective in hyperopia. This is my clinical impression; it is not a claim of superiority over LASIK, and the published data are limited, as I describe below.

The basis in the literature is a multicentre study in which 374 eyes of 199 patients were followed for 12 months. The inclusion limit was up to +6.00 D of sphere and up to 5.00 D of cylinder. At 12 months, 81% of eyes were within ±0.50 D of target and 93% within ±1.00 D; 1.2% of eyes lost two or more lines of corrected vision.[8] Hyperopia data with the new-generation device are still very limited: one published pilot study includes only 11 eyes of 7 patients; at 3 months, 72.7% of eyes were within ±0.50 D, and 36.4% had a one-line decrease in corrected vision; no eye lost two or more lines.[9] In hyperopia the data are fewer and newer than in myopia; this is why, in this group, I discuss expectations at the outset.

Who is it not suitable for?

Keratoconus, or a suspicion of it, on corneal topography

This is the first non-negotiable heading. Keratoconus is a disease in which the cornea thins and becomes cone-shaped of its own accord; removing tissue from such an eye can speed up the process. In a series of 6,619 eyes that examined ectasia after SMILE, 8 of the 10 eyes that developed ectasia were eyes whose preoperative map was "borderline".[10] If there is a suspicion, I do not perform laser surgery; we clarify the suspicion first. If topography raises a suspicion of keratoconus: keratoconus information (in Turkish)

Thin cornea or insufficient remaining tissue

If the cornea is below 480 µm, or if the calculation shows that a bed of less than 270 µm would be left after the lenticule, I do not perform SMILE Pro (my own thresholds; the sources are above). I do not push the limit: ectasia is a problem that can appear years later and is difficult to treat.

Prescription outside the range, or still changing

I do not perform SMILE Pro for myopia above −10.00 D or astigmatism above −5.00 D (my own limits). The astigmatism limit in the US registration is −3.00 D;[1] between −3.00 and −5.00 D is my own clinical practice, above that registration. And in an eye whose prescription has changed in the past year, the value I correct today will fall short tomorrow. In that eye, I wait.

Marked dry eye, active ocular surface disease

Every laser method cuts some of the corneal nerves and can disturb the tear balance for a while. In someone who already has marked dry eye, this period can be harder; the measurements can also be misleading. I treat the ocular surface first and repeat the measurements afterwards. I also do not operate while there is an active infection or inflammation.

Pregnancy and breastfeeding

Because hormonal changes during pregnancy and breastfeeding can temporarily shift the prescription and the corneal measurements, I postpone the procedure. In the literature there is also a single case report of a patient whose vision began to deteriorate in the first trimester of pregnancy, 11 months after SMILE, and who was subsequently found to have ectasia in both eyes;[11] a single case does not allow generalisation, but it is enough for me to be cautious. I wait 2 months after breastfeeding has ended (in my practice).

What I suggest if you are not suitable

The sentence "you are not suitable for SMILE Pro" does not have to mean "carry on with glasses". If the cornea is thin but its map is regular, surface laser (PRK), which spends no tissue on a flap or a lenticule, is considered as an option; its healing is slower and the first days are more demanding. This route applies to myopia: I do not perform PRK for hyperopia; there, my options are LASIK and SMILE Pro.

If the prescription is very high, or the cornea does not allow any laser, an implantable lens placed inside the eye (ICL), which does not touch the cornea, comes up as a separate assessment; it has its own reasons for refusal too. ICL for those found unsuitable for laser: who it is for, and who it is not (in Turkish)

Assessment day: which measurement do I look at, and why?

Corneal topography

A map of the front and back surfaces of the cornea. What I look at is shape: is one area steeper than the others, is there a forward bulge on the back surface, do the two eyes resemble each other. This measurement carries the most weight in the decision.

Corneal thickness (pachymetry)

I look at the thickness at the thinnest point, not at the centre. When this number is set beside the lenticule thickness your prescription requires, the residual bed and the percent tissue altered are calculated.

Examination with drops, pupil diameter, tear tests

In the examination with drops, the pupil is dilated and the focusing muscle of the eye is temporarily relaxed; this way I measure your true prescription and also examine the retina in detail. I measure pupil diameter in dim light; although the link between a large pupil and seeing halos at night is debated in the literature, I discuss this with you in advance. The tear tests answer the dry eye question I described above.

Before the appointment: when to stop wearing contact lenses

The rule I apply in my practice: stop wearing your soft lenses 5 days before the measurements, and your rigid (gas-permeable) or toric lenses 2 weeks before, and do not put them back in until the surgery. The reason is not the device. A lens temporarily changes the shape of the cornea and can also make the epithelium (the outermost protective layer of the eye) more sensitive. The aim is not the surgery itself but accurate measurements (topography, prescription, thickness): the laser is planned for the eye that was measured; the eye that is measured and the eye that is operated on must be the same. My view: of the two periods, the more important one is the time before the measurements, because the plan is made from those measurements. Even if you are obliged to wear lenses after the measurements, this period before them (5 days for soft lenses, 2 weeks for rigid or toric lenses) must be spent without lenses. This does not mean that lenses are permitted after the measurements; my recommendation does not change: do not wear them until the surgery.

The periods given in the sources are longer than the ones I apply; I am not hiding the difference. The FDA's patient information page for LASIK says, before the initial evaluation, 2 weeks for soft lenses, at least 3 weeks for toric soft and gas-permeable lenses, and at least 4 weeks for hard lenses.[18] In a study that followed 42 eyes of 21 soft lens wearers being assessed for refractive surgery, no significant change was seen after the first measurement in 26 eyes, while in the remaining 16 eyes the cornea took at least 3 days to settle; the authors state that a 2-week lens-free period appears sufficient, but that, because it cannot be predicted for the individual, repeating the measurement is safer.[12]

Procedure day, step by step

The procedure is performed under anaesthetic drops; there is no needle and no general anaesthesia. I treat both eyes in the same session; the total time is 7-13 minutes (in my practice). This is what happens, in order:

1. Preparation. Anaesthetic drops are instilled, and the eyelids are held open with a small device. You will feel the urge to blink but will not be able to; this is uncomfortable but brief.
2. The laser phase. The device's patient interface (contact glass) approaches the eye and holds it steady with gentle suction. This part, which touches the eye, is a single-use sterile patient interface opened new for each patient; it is not used on another patient. During this you will feel pressure, and the light you are looking at may dim or go dark for a short time. Creating the lenticule takes seconds.[2] The only thing I ask of you is to keep looking at the light.
3. Removing the lenticule. The suction is released. I separate the lenticule and take it out through the small incision. There is a sensation of touch and slight pulling; sharp pain is not expected.
4. Afterwards. After a short rest and a check, you go home the same day. Have someone with you; you cannot drive that day.

The suction letting go part-way through the laser phase (suction loss) is rare but well known: in a SMILE Pro series of 916 eyes it occurred in 6 eyes (0.66%); the procedure was completed as planned in 911 of the 916 eyes.[13] We discuss before the procedure what would be done in such a case.

After the procedure: first day, first week, first month

First day

In the first hours, stinging, watering and sensitivity to light are usual. Vision is hazy that day; clarity mostly improves starting from the next day, but do not come expecting "everything in place by the next day". Not rubbing the eye is the most important rule of this period. I do the first check the day after the procedure. You will use two different drops for 1 month (in my practice).

First week

Clarity can fluctuate during the day; vision that is good in the morning and tired in the evening is commonly described. A feeling of dryness can be noticeable in this period. The periods I apply in my practice: driving after 3 days, return to work after 3-7 days. For the first 5 days water must not touch the eye (you can shower; protect your face and your eye from the water); after day 5 it can.

First month and check-ups

It can take weeks for vision to settle; this is a known feature of the method. The check-up schedule I apply in my practice: day 1, week 1, month 1, month 6 and year 1. At the check-ups I look at vision, the remaining prescription and the ocular surface. I ask you to wait 2 weeks for eye make-up, sport and swimming (in my practice).

SMILE Pro, LASIK and PRK side by side

The basis for the dry eye row is a meta-analysis of 18 studies comparing SMILE with femtosecond LASIK: tear break-up time at 3 months was found to be 3.267 seconds longer in favour of SMILE; in the questionnaire score that measures the patient's own symptoms (OSDI), however, the difference is not statistically significant.[14] In other words, there is a difference in the measurement, but no proven difference in the symptoms felt.

This table does not answer "which is better"; it answers "which one for which eye". There are times when I discuss a different method even for the two eyes of the same person. The other laser methods we perform (in Turkish)

How long it lasts is a separate question: a prescription corrected by laser can come back to some extent over the years, and this likelihood varies with the method and the starting prescription. I have described it, with the figures, in a separate article: Does the prescription come back, and is there a difference between methods? (in Turkish)

SMILE Pro, SILK, SmartSight, CLEAR: what is the difference?

All four belong to the same family of methods: the laser separates a lenticule inside the cornea, and the surgeon removes it through a small incision. Their common name in the literature is keratorefractive lenticule extraction (KLEx). The names differ because the devices differ. I use the VisuMax 800; read the comparison below with that in mind.

The times were taken from the table of a peer-reviewed review comparing the five platforms;[19] they are values compiled from different sources, not a side-by-side measurement made in the same eyes. For the VisuMax 800, the time measured in the study I mentioned above was 9.47 seconds.[2]

What this means for you is this: as the cutting time gets shorter, the time your eye has to stay still under suction gets shorter. What it does not mean is this: there are no data showing that a shorter time gives better vision. When the two generations of the same device were compared, no significant difference emerged in the visual outcome even though the time was markedly shorter.[3] The review I mentioned also concludes that all five platforms demonstrate safety, efficacy and refractive stability; at 6 months, more than 85% of eyes with CLEAR, SILK, SMILE and SMILE Pro are within ±0.50 D of target.[19]

For the newer platforms the published data are fewer, and most are at the level of case series. In the randomised study comparing CLEAR with classic SMILE in the two eyes of the same patients, no significant difference was found in the ocular surface measurements over one year.[23] No randomised study directly comparing the four devices in terms of visual outcome was found in the PubMed search carried out while this page was being prepared.

Risks and limits

The temporary ones

Dryness, blurring in the first days, and halos or scatter around lights at night are the three complaints I discuss most often. In the SMILE Pro series of 916 eyes, the most commonly recorded events in the first 3 months were punctate staining of the surface (superficial punctate keratitis, 3.51%) and dry eye (1.32%); after 3 months, dry eye was reported at 1.65% and flashes of light, halo or glare at 0.88%. No sight-threatening complication was seen in the same series.[13] These are retrospective, early-period data from a single centre; long-term follow-up is not yet available.

The possibility of an enhancement, and how it is done

The target is not hit exactly in every eye. In the same SMILE Pro series, retreatment was performed in 14 of the 916 eyes (1.54%): 11 with LASIK, 2 with an intraocular lens, 1 with cataract surgery.[13] In another study that followed 524 eyes with classic SMILE, the incidence of enhancement was 2.1% at 1 year and 2.9% at 2 years; being over 35 years of age, myopia above 6.00 D and astigmatism above 3.00 D were among the factors that increased the risk.[15]

If a prescription remains in myopia, I do the enhancement on the surface, with PRK (the method I use in my practice); in the study I mentioned, too, all of the enhancements were performed with PRK.[15] I do not perform PRK for hyperopia; if an enhancement is needed in this group, we discuss the method at the examination. For this I first wait for the prescription to settle and measure the remaining corneal tissue again. If the tissue does not allow it, I do not do an enhancement.

The rare but serious ones

Ectasia. Thinning and forward bulging of the cornea months or years after the procedure. In a SMILE series of 6,619 eyes it was seen in 10 eyes (0.15%; on average 21.3 months later). The abstract of the study gives the rate in eyes whose map was classified as borderline as 0.80% (8 of 999 eyes); however, of these 999 eyes, 594 had SMILE alone and 405 had SMILE combined with cross-linking, and no ectasia was seen in the second group.[10] A systematic review pooling published cases calculated the incidence in eyes with no identifiable preoperative risk factor as 11 per 100,000 eyes;[16] because this calculation rests only on published cases, it may understate the true incidence. The fact that 8 of the 10 eyes that developed ectasia in the first series had borderline maps says this: an important part of this risk is managed not on the operating table but on assessment day.

Infection. Rare, but it can affect vision permanently. In SMILE, because the infection settles inside the cornea, in a layer that drops reach with more difficulty, it becomes harder to treat.[17] If you have increasing pain, redness or a drop in vision after the procedure, do not wait for the check-up day; call the same day.

What the laser does not change

The laser corrects the prescription you have today; it does not stop the eye from ageing. In the forties near vision becomes harder (presbyopia), and someone who sees in the distance without glasses will also need reading glasses. The development of cataract at an older age, and the need for regular retinal checks in high myopia, are not changed by the laser either. This is the reason for my upper limit of 45 years. If you accept wearing reading glasses, I do not apply an upper age limit.

Frequently asked questions

References

1. U.S. Food and Drug Administration. Premarket Approval P150040/S003, VisuMax Femtosecond Laser, decision date 4 October 2018 (approval text: indication and prescription range). FDA PMA record P150040/S003
2. Yang X et al. "Comparison of early clinical and optical quality-related outcomes after SMILE using VisuMax 800 versus VisuMax 500 for myopia and low-to-moderate astigmatism in a Chinese population." Frontiers in Medicine, 2026. PMID 42145766
3. Wan Q, Wei R, Chen L, Ma K. "Comparison of VISUMAX 800 and VISUMAX 500 Femtosecond Laser Systems for Myopia: A Systematic Review and Meta-Analysis." Journal of Clinical Medicine, 2026. PMID 42513431
4. Hu J et al. "Comparison of lenticular scanning quality and visual outcomes of keratorefractive lenticule extraction between VisuMax 800 and 500 systems." Journal of Cataract & Refractive Surgery, 2026. PMID 41742367
5. U.S. National Library of Medicine, AccessGUDID. VISUMAX, model "VISUMAX 800", Carl Zeiss Meditec AG; associated submission P150040, supplement no. 012 (FDA decision date 10 January 2024). GUDID record 04049471095111
6. Santhiago MR et al. "Association between the percent tissue altered and post-laser in situ keratomileusis ectasia in eyes with normal preoperative topography." American Journal of Ophthalmology, 2014. PMID 24727263
7. Randleman JB, Trattler WB, Stulting RD. "Validation of the Ectasia Risk Score System for preoperative laser in situ keratomileusis screening." American Journal of Ophthalmology, 2008. PMID 18328998
8. Reinstein DZ, Sekundo W, Archer TJ et al. "SMILE for Hyperopia With and Without Astigmatism: Results of a Prospective Multicenter 12-Month Study." Journal of Refractive Surgery, 2022. PMID 36476297
9. Chung HY, Chung YT, Kim BK, You IC. "Early Clinical Outcome of Hyperopic Small Incision Lenticule Extraction (SMILE) Using the VisuMax 800 in South Korea: A Pilot Study." Korean Journal of Ophthalmology, 2026. PMID 41725200
10. Brar S, Roopashree CR, Ganesh S. "Incidence of Ectasia After SMILE From a High-Volume Refractive Surgery Center in India." Journal of Refractive Surgery, 2021. PMID 34914554
11. Huang TZ, Jin HY. "Case Report: Bilateral Corneal Ectasia Developed during Pregnancy after Small-incision Lenticule Extraction." Optometry and Vision Science, 2022. PMID 35149635
12. Hashemi H, Firoozabadi MR, Mehravaran S, Gorouhi F. "Corneal stability after discontinued soft contact lens wear." Contact Lens & Anterior Eye, 2008. PMID 18343184
13. Beckers D et al. "Intraoperative Safety and Postoperative Complications After SMILE Pro: A Retrospective Case Series of 916 Eyes." Journal of Clinical Medicine, 2026. PMID 42355753
14. Chen KY, Chan HC, Chan CM. "How Effective is Keratorefractive Lenticule Extraction Surgery (KLEx) in Reducing Dry Eye Outcomes Compared to LASIK?: A Systematic Review and Meta-analysis." Journal of Refractive Surgery, 2025. PMID 40778870
15. Liu YC, Rosman M, Mehta JS. "Enhancement after Small-Incision Lenticule Extraction: Incidence, Risk Factors, and Outcomes." Ophthalmology, 2017. PMID 28318639
16. Moshirfar M et al. "Ectasia After Corneal Refractive Surgery: A Systematic Review." Ophthalmology and Therapy, 2021. PMID 34417707
17. Anitha V et al. "Current perspectives on infections following refractive kerato-lenticule extraction (KLex) surgery." Indian Journal of Ophthalmology, 2025. PMID 40243076
18. U.S. Food and Drug Administration. "What should I expect before, during, and after surgery?" (LASIK patient information page; accessed 11 October 2026). FDA: before, during and after LASIK
19. Miller SM, Sitto MM, Moin KA, Hoopes PC, Moshirfar M. "Comparing The Existing Myopic Keratorefractive Lenticule Extraction (KLEx) Platforms: A Narrative Review." Clinical Ophthalmology, 2025 (cutting times from the table in the full text). PMID 40661247
20. Ozkan J, Shroff R et al. "Real-World Study Assessing the Efficacy and Safety of a Novel KLEx Procedure with a Next-Generation Femtosecond Laser for Refractive Error Correction." Clinical Ophthalmology, 2026. PMID 41815634
21. Arifaizha N, Adji MWK, Rachmani AV, Pujiastuti S. "Visual Outcomes of SmartSight (SCHWIND ATOS) Refractive Surgery in the Correction of Myopia and Myopic Astigmatism: A Systematic Review." Journal of Refractive Surgery, 2026. PMID 42573219
22. Bteich Y, Assaf JF, Gendy JE, Awwad ST. "Keratorefractive Lenticule Extraction Using the Ziemer FEMTO LDV Z8 Platform (CLEAR): One-Year Results." Journal of Refractive Surgery, 2024. PMID 39530987
23. Yu M et al. "Randomized controlled trial on corneal denervation, neuroinflammation and ocular surface in corneal lenticule extraction for advanced refractive correction (CLEAR) and small incision lenticule extraction (SMILE)." Eye and Vision, 2025. PMID 40165267