What Is SMILE (KLEx)?

SMILE (KLEx) is a flapless laser eye surgery technique: a femtosecond laser shapes a small, lens-like piece of corneal tissue — a lenticule — within the inner cornea, then removes it through an incision only a few millimetres wide. KLEx, short for keratorefractive lenticule extraction, describes the same technique. SMILE is one of the newer laser eye surgery methods and, unlike femtosecond LASIK, does not involve lifting a wide surface layer (a flap); the whole procedure takes place within the cornea using a single laser, associated with less disruption to the corneal nerve network.

SMILE is one of the modern laser eye surgery techniques, used clinically for myopia and astigmatism, not hyperopia. PRK, femtosecond LASIK and SMILE aim for the same outcome by different routes; SMILE is set apart by creating no flap and using a far smaller incision. Which technique suits you is decided at the assessment, based on corneal thickness, corneal topography and the type of refractive error.

SMILE is considered for patients with myopia and/or astigmatism who prefer a flapless, smaller-incision technique, and whose corneal structure is suitable. It is not the clinical choice for hyperopia, for which femtosecond LASIK or PRK is used instead. The profiles below are commonly seen among SMILE candidates, though final suitability is only confirmed at assessment. Patients with regular corneal topography and stable eye health are a reasonable starting point. In pregnancy or breastfeeding, the procedure may be postponed, as hormonal changes can temporarily affect visual clarity.

After anaesthetic drops are applied, the patient lies under the laser device with the eye positioned on a fixed target. The femtosecond laser shapes a lens-like piece of tissue — the lenticule — within the cornea, at a depth and shape calculated beforehand; this takes around twenty to thirty seconds. A small incision, around 2-4 mm, is then made, and the surgeon carefully separates and removes the lenticule through it with a fine instrument. Because no flap is created, the corneal nerve network is largely preserved, meaning more limited dry eye in some patients afterwards. The procedure takes only a few minutes per eye, and the patient goes home the same day.

1. 1Anaesthetic drops and positioning. The surface of the eye is numbed and the patient is positioned under the laser device.
2. 2Creating the lenticule. The femtosecond laser shapes a lens-like piece of tissue within the cornea; this step takes around 20-30 seconds.
3. 3Making a small incision. A small incision of around 2-4 mm is made in the cornea.
4. 4Removing the lenticule. The lenticule is then carefully removed through this incision using a fine instrument.

The advantage of SMILE lies in its very small incision and the absence of a flap; in some patients, this benefits dry eye. Its limitation is that it cannot treat hyperopia and may not suit every corneal structure. The diagram below compares the incision size of SMILE with the flap opening of femtosecond LASIK; PRK involves no separate incision, as it works by direct surface ablation. A smaller incision also leaves more corneal surface intact.

In most patients, recovery progresses relatively quickly, with noticeably clearer vision often reported within the first day. Because the incision is small, some patients find the first few days more comfortable. As no flap is created, the corneal nerve network is largely preserved, meaning more limited dry eye in some patients than after femtosecond LASIK. Full visual stability may take days to weeks, varying from person to person. Follow-up appointments are usually set at the first day, one week and one month.

Risks include infection, temporary fluctuations in vision, a visual outcome different from what was predicted, and, rarely, technical difficulty removing the lenticule. These occur at a low frequency, with more detail given at the assessment. Rarely, an additional manoeuvre may be needed during lenticule removal, managed by the surgeon at the time. Using the prescribed drops correctly and keeping follow-up appointments help catch complications early. Light sensitivity and a temporary sensation of halos and glare at night are reported by some patients in the first weeks and tend to ease over time. Temporary irritation at the incision site occasionally occurs and usually settles by itself.

Alternatives to SMILE include TransPRK (no-touch PRK) and femtosecond LASIK; for hyperopia, one of these two is used instead. In borderline corneal thickness, flapless PRK may stand out, while femtosecond LASIK may suit those who prioritise faster visual recovery. The type and degree of refractive error can also guide the choice, with separate content on myopia and astigmatism. The most suitable alternative becomes clear through topography and pachymetry measurements at assessment.

How SMILE compares with PRK and femtosecond LASIK — in incision size, dry eye risk and speed of recovery — is covered in separate comparison content. A general overview of which technique may suit you is available in the laser suitability assessment and technique decision guide. For patients who value a very small incision, or who have a history of dry eye, the difference from femtosecond LASIK is worth reviewing before deciding.

To find out whether SMILE is right for you, request an appointment at Op. Dr. Anıl Kaya's practice in Istanbul through the contact page. At the assessment, corneal thickness, corneal topography and the type of your refractive error are considered together to clarify which technique suits you. The initial visit also covers your dry eye history and daily habits.