SMILE. What the literature actually says.
Flapless, minimally invasive, with a smaller but increasingly mature evidence base. A short, honest read on what randomised trials and 5-year cohorts report — and where the data is still being built.
What it is.
SMILE — small-incision lenticule extraction — corrects refractive error by removing a precisely cut lenticule of corneal stromal tissue through a 2-4 mm side incision. There is no flap. A single femtosecond laser performs the lenticule cut and the side incision in one docking; the surgeon then dissects and extracts the lenticule through the incision with a manual instrument.
The technique exists because the absence of a flap addresses two specific concerns with LASIK: corneal biomechanical weakening (less anterior stromal disruption preserves more tensile strength) and post-operative dry eye (the small incision spares more corneal nerve plexus). Both signals have been characterised in randomised contralateral-eye trials. The trade-off is a steeper surgeon learning curve and slower early visual recovery than LASIK.
The technique.
An ESCRS-credentialed refractive surgeon assesses the same pre-operative variables as for LASIK — tomography, pachymetry, manifest and cycloplegic refraction, tear-film status — plus a specific check that the lenticule profile will leave the residual stromal bed above safe thresholds for the target correction.
The Zeiss VisuMax 800 femtosecond laser docks once, cuts the posterior lenticule surface, then the anterior surface, then a 2-4 mm side incision. The VisuMax 800 platform delivers the cut at 2 MHz pulse frequency, which compresses the laser portion of the case to approximately 10 seconds per eye. The surgeon then enters the small incision with a dissector, separates the lenticule from surrounding stroma, and removes it through the same incision.
Total room time is 20 minutes per eye in our protocol. Vision is functional within 4-24 hours but sharpens over 1-2 weeks — slower than LASIK in the very early window. The patient receives preservative-free lubricant drops, topical antibiotic, and a short steroid taper. The small incision typically seals without sutures within hours.
What the outcomes data shows.
Dry eye is where SMILE shows the most consistent advantage. A 2022 prospective randomised contralateral-eye trial by Ma et al. (American Journal of Ophthalmology, n=80 eyes / 40 patients) demonstrated more corneal denervation in LASIK eyes than SMILE eyes at 1, 3, and 6 months. A meta-analysis (PLOS One, 2016) pooling six studies (291 SMILE eyes vs 277 FS-LASIK eyes) found tear break-up time and ocular surface disease index were significantly worse in the LASIK arm at follow-up, while Schirmer's and tear osmolarity did not differ.
Refractive efficacy at the 5-year mark is well-characterised for moderate myopia. Ağca et al. (Journal of Ophthalmology, 2018, n=37 eyes) reported 5-year outcomes in high myopia (preoperative SE ≥ −6.00 D): 59% of eyes within ±0.50 D, 92% within ±1.00 D, with safety and efficacy indices remaining favourable. Reinstein et al. (Journal of Refractive Surgery, 2022, n=187 eyes, 181 with 12-month data) extended SMILE to high myopic astigmatism with 57% achieving 20/20 or better uncorrected — a more difficult population with predictably lower acuity figures.
Biomechanical and stability data continue to favour SMILE over LASIK for thinner corneas and higher corrections. A 2017 network meta-analysis (Shen et al., American Journal of Ophthalmology) ranked SMILE comparably to FS-LASIK on efficacy and visual quality, with the post-operative biomechanical profile being the meaningful differentiator for cornea-at-risk patients.
What we still study.
Long-term refractive stability beyond 7 years is still maturing. Published cohorts run to 5 and 7 years for moderate myopia and to 5 years for high myopia. There is regression with extended follow-up — modest in moderate corrections, more visible at SE > −9.00 D. SMILE retreatment options (PRK over a SMILE cap, or a circle conversion to a LASIK flap) are technically available but less standardised than primary LASIK retreatment.
Hyperopic SMILE and SMILE-pro for very high myopia are active research areas. The current commercial indication concentrates on myopia and myopic astigmatism within validated dioptre ranges; treatments outside that envelope are not yet routine.
The Hektor protocol.
We use SMILE selectively — typically for patients with thinner corneas, dry-eye-prone tear-film profiles, or athletes and military candidates where a flapless cornea is the deciding factor. For straightforward low-to-moderate myopia in a robust cornea, LASIK with the Amaris 1050RS remains our default; we recommend SMILE when the biomechanical or dry-eye signal favours it.
Cases run on the Zeiss VisuMax 800 — 20 minutes per eye, recovery suite by 09:30, discharge by midday. Structured video review at 24 hours, 1 week, 1 month, 3 months, and 12 months.
- ·Stable refraction for 12+ months (≤0.50 D change in the past year)
- ·Myopia −1.00 to −10.00 D, myopic astigmatism up to −5.00 D
- ·Normal corneal tomography (Pentacam Scheimpflug, no keratoconus signatures)
- ·Adequate residual stromal bed prediction (≥280 μm after lenticule extraction)
- ·Age 18+ (typically 21+ for stability margin)
- ·Adequate-to-borderline tear film — SMILE preserves more corneal nerve plexus than LASIK
- ·Athletes, military candidates, or patients where flap-displacement risk is unacceptable
- —Hyperopia of any magnitude — SMILE corrects myopia and myopic astigmatism only
- —Keratoconus or forme fruste keratoconus on tomography
- —Insufficient residual stromal bed prediction or thin pre-op corneas outside the SMILE envelope
- —Significant dry eye disease (uncontrolled MGD, Sjögren's, severe SPK)
- —Active uveitis, untreated glaucoma, or retinal pathology requiring intervention
- —Pregnancy or breastfeeding (refraction can shift transiently)
- —Patients unwilling to accept slower 1-2 week visual recovery compared to LASIK
Pure hyperopia or mixed astigmatism: referred to LASIK — SMILE does not correct hyperopic refractive error at our centre.
Mild irregular topography with otherwise normal screening: referred to PRK or ICL, not stretched into a SMILE indication.
Patients who need fastest possible visual recovery (e.g. operating heavy machinery within 48 hours): LASIK is the honest answer, not SMILE — the day-1-to-day-7 acuity curve is genuinely slower with SMILE.
Recovery, by milestone.
Compared to alternatives.
LASIK has 20+ years more outcomes data, faster day-1 visual recovery, easier retreatment via flap lift, and corrects hyperopia (SMILE does not). SMILE preserves more corneal nerve plexus (better dry-eye trajectory in contralateral-eye RCTs) and more anterior stroma (modest biomechanical advantage). For a robust cornea and a typical myopia, both are good answers; we let the patient profile decide.PMID 35594919
PRK has no flap, no lenticule — surface ablation only. Long-term safety is excellent. Recovery is slower (3–5 days of significant discomfort, weeks of haze risk). For thin corneas borderline for SMILE, PRK is the safer choice and our default referral.
For corrections above approximately −10.00 D or for corneas the laser cannot safely treat, ICL is the better answer. Reversible. Long-term endothelial cell loss (~1.1% / year vs ~0.5% control) is a real consideration disclosed at consultation.PMID 38194352
Lifestyle decision, not a safety one. SMILE does not eliminate the need for reading glasses after age 40 — presbyopia is a different optical problem. The honest framing: SMILE reclaims roughly 25–30 hours / year of lens-care time while leaving the cornea biomechanically closer to its native state than LASIK.
- ·Bilateral SMILE procedure (both eyes)
- ·Pre-op screen: Pentacam tomography, OCT, manifest + cycloplegic refraction, tear-film assessment, lenticule-profile residual-bed calculation
- ·Zeiss VisuMax 800 laser time
- ·Post-op medication kit (preservative-free lubricants, antibiotic, short steroid taper, eye shields)
- ·24-hour video check with the operating surgeon before your flight
- ·Structured follow-up at week 1, month 1, month 3, and month 12
- ·Translator (8 languages) + airport transfers + optional hotel night
UK/US/EU figures are typical-range benchmarks for premium private refractive clinics running Zeiss VisuMax platforms — not Hektor quotes. Sourced from publicly published 2025–2026 clinic price pages.
Our Istanbul figure is a locked bilateral package — one number, paid once. Toric correction within the SMILE envelope does not trigger a per-eye surcharge.
Common questions.
Is SMILE better than LASIK?+
Can SMILE correct my hyperopia?+
Does SMILE hurt?+
Why is recovery slower than LASIK on day one?+
What if my prescription is too high?+
Can SMILE be redone if regression occurs?+
How long is the long-term safety data for SMILE?+
Will I be free of glasses forever?+
Why is Istanbul cheaper than the UK or US for SMILE?+
How long do I need to stay in Istanbul?+
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