What Is Femto LASIK?

Femto LASIK is a laser vision correction technique in which a femtosecond laser first creates a thin corneal flap, lifts it so a laser can treat the tissue underneath, then lays it back into place. It is the most widely performed flap-based technique in laser eye surgery, used in millions of eyes worldwide over several decades. The femtosecond laser shapes the flap with precise, computer-controlled light pulses rather than a mechanical blade, keeping its thickness and shape consistent. Once lifted, an excimer laser reshapes a calculated amount of the underlying tissue (the stroma) so light focuses more clearly on the retina; the flap then adheres naturally as healing begins.

Femto LASIK is one of three main laser eye surgery techniques, used to correct myopia, hyperopia and astigmatism. PRK, Femto LASIK and SMILE reach the same goal by different routes, differing in how the laser reaches the cornea, whether a flap is created, and how healing unfolds. Femto LASIK's key difference is that, thanks to the flap, vision typically sharpens within the first day. The right technique is decided during examination, weighing corneal thickness, topography and lifestyle together; detailed comparisons are covered in separate articles.

Femto LASIK may be considered for patients with adequate corneal thickness, no significant dry eye, and a preference for a short recovery. Because a flap is created, corneal thickness must be above a certain threshold, confirmed during examination through topography and pachymetry. The profiles below are commonly seen in Femto LASIK assessments, though final suitability is confirmed only after examination. Stable eye health with no irregular corneal curvature is a reasonable starting point. In pregnancy or breastfeeding, the procedure may be postponed, as hormonal changes can temporarily affect visual sharpness.

Before the procedure, the eye is numbed with anaesthetic drops so no pain is felt. A femtosecond laser creates a thin flap, roughly 100-120 microns thick, in the upper cornea, leaving a hinge so it can be lifted. An excimer laser then reshapes a calculated amount of the underlying tissue (the stroma). The flap is laid back into place and adheres naturally, with no stitches required. The procedure is quick for a single eye, and patients can usually go home the same day.

1. 1Anaesthetic drops. The surface of the eye is numbed with drops, so no pain is felt.
2. 2Femtosecond laser creates the flap. Precise pulses of light create a thin, hinged flap in the upper layer of the cornea.
3. 3Excimer laser reshaping of the stroma. A personally calculated amount of the underlying corneal tissue is reshaped.
4. 4The flap is repositioned. The flap is laid back into place and adheres naturally, with no stitches needed.

Femto LASIK's advantage is that, thanks to the flap, vision typically sharpens quickly, with less discomfort in the first few days than PRK. Its limitation is that a flap may not suit thin corneas or certain eye structures; the flap uses part of the corneal thickness, and the remaining tissue must be enough for the laser treatment itself. The chart below shows the flap's thickness relative to average corneal thickness, which is why PRK may be considered instead when thickness is borderline.

Most patients notice a marked improvement in vision within the first day; mild stinging and watering usually ease within a few days. Full visual stability can take several weeks and varies by patient. Because a flap is used, the epithelium heals faster than with PRK, so most patients return to daily activities sooner. Since the flap stays vulnerable to impact in the early days, it is important to avoid activities that risk eye contact for as long as advised. Follow-up visits are usually set at the first day, one week and one month, to confirm the flap is healing well.

Risks include rare flap-related complications (wrinkling or displacement), temporary dry eye, infection risk, and a visual outcome that differs from what was expected. These are uncommon but discussed in detail during examination. Because the flap stays vulnerable to impact in the early days, certain precautions are needed during recovery; using prescribed drops consistently and keeping follow-up appointments help catch complications early. Rarely, a temporary wrinkle at the flap edge or a fine fold underneath can occur, usually noticed and corrected early. Light sensitivity and temporary night-time halos or glare are also reported by some patients in the first few weeks, easing over time.

TransPRK (no-touch PRK) and SMILE (KLEx) can be considered as alternatives to Femto LASIK. The suitable technique depends on corneal structure, dry eye history, and personal priorities. In borderline corneal thickness, flapless TransPRK may be preferred, while SMILE, working through a smaller incision, offers a different balance; detailed comparisons are covered in separate articles. Refractive error type and degree also influence the choice; myopia, hyperopia and astigmatism are each covered in their own articles.

How Femto LASIK compares with PRK and SMILE - recovery time, how the first few days feel, and flap-related differences - is covered in separate comparison articles. A general overview of which technique may suit you is in the laser eye suitability examination and technique decision guide. For borderline corneal thickness, or higher risk of eye contact in daily life, the difference between PRK and Femto LASIK should be reviewed before a final decision.

To find out whether Femto LASIK suits you, request an appointment at Op. Dr. Anıl Kaya's practice in Istanbul through the contact page. During examination, your corneal thickness, topography and prescription are assessed together to identify the most suitable technique. The first visit also covers your dry eye history and daily habits.