SMILE Eye Surgery: Small Incision Lenticule Extraction Explained

How SMILE Works: Lenticule Removal

SMILE (Small Incision Lenticule Extraction) is a third-generation laser refractive procedure developed by Carl Zeiss Meditec using the VisuMax femtosecond laser. Unlike LASIK (which creates a flap and then ablates with an excimer laser) or PRK (which ablates the surface), SMILE creates a precisely shaped disc of corneal stroma — called a lenticule — entirely within the intact cornea using femtosecond laser pulses. This lenticule, which has the exact shape and thickness needed to correct the refractive error, is then removed through a 2–3 mm arc incision in the cornea without creating a full flap.

The entire procedure uses only the femtosecond laser — no excimer laser is needed. The femtosecond laser creates both the lenticule plane and the small arc incision. The surgeon uses an instrument to separate the lenticule from the surrounding stroma and extracts it through the incision. Removing the lenticule changes the corneal curvature and corrects the prescription — without any flap, without excimer laser ablation, and with only a 2–3 mm wound rather than a flap perimeter of 22–27 mm.

No Flap: Structural and Safety Advantages

SMILE's most significant structural advantage is preservation of the anterior corneal stroma — the strongest part of the cornea. LASIK's flap severs the anterior stromal lamellae, which are highly cross-linked and contribute most to corneal tensile strength. SMILE leaves the anterior stroma (including Bowman's layer and the first 80–100 microns of anterior stroma) entirely intact. Biomechanical studies show SMILE corneas retain greater tensile strength than post-LASIK corneas, which is theoretically beneficial for long-term ectasia prevention — though clinical ectasia rates are very low with both procedures in properly selected patients.

Additionally, eliminating the flap eliminates all flap-related complications: no flap displacement from trauma, no flap striae, no diffuse lamellar keratitis (DLK), no flap interface epithelial ingrowth. This makes SMILE particularly attractive for contact sport athletes and active military personnel — the same population that typically benefits from PRK. Unlike PRK, SMILE offers rapid recovery similar to LASIK.

Lower Dry Eye Risk: The Clinical Advantage

Multiple randomized controlled studies comparing SMILE and LASIK consistently demonstrate significantly lower dry eye induction with SMILE. The mechanism: SMILE's small arc incision disrupts far fewer corneal sensory nerve fibers than LASIK's full-circumference flap incision, preserving more of the lacrimal reflex. Published studies show:

• SMILE patients have higher Schirmer test results at 1, 3, and 6 months post-operatively
• TBUT is better preserved with SMILE at all measured timepoints
• Corneal nerve density recovers faster after SMILE than LASIK (measurable by confocal microscopy)
• Fewer SMILE patients require prescription dry eye treatment post-operatively

For patients with pre-existing dry eye risk factors, SMILE is a clinically preferred alternative to LASIK. See LASIK vs SMILE comparison.

FDA Approval and Platform Availability

SMILE was FDA-approved in the United States in 2016 for myopia and myopic astigmatism. It is performed exclusively on the VisuMax femtosecond laser (Carl Zeiss Meditec). SMILE is widely available at most major LASIK centers and academic ophthalmology programs in the U.S. It has been performed globally since 2011 with over 5 million procedures worldwide as of 2026.

Ideal Candidates for SMILE

SMILE is currently approved for myopia (up to -10 D) and myopic astigmatism (up to 5 D cylinder). It is not currently FDA-approved for hyperopia treatment. SMILE is the preferred choice for patients with: dry eye risk factors or pre-existing mild dry eye; active lifestyles with contact sport or trauma risk; myopia within the approved range; and desire for a technologically advanced flap-free procedure with rapid recovery.

Clinical Outcomes vs LASIK

SMILE and LASIK show equivalent visual outcomes for myopia correction in multiple comparative studies:

• Both achieve 20/20 or better in 95–98% of myopic patients
• Contrast sensitivity and higher-order aberration profiles are similar at 12 months
• SMILE shows lower dry eye incidence and better tear film stability (significant advantage)
• SMILE has lower night-driving difficulty in some studies
• LASIK has faster visual recovery in the first 1–3 days (SMILE recovery is 1–3 days vs 24 hours for LASIK)

Cost of SMILE Surgery

SMILE typically costs $2,500 to $3,500 per eye — similar to or slightly more than bladeless LASIK, reflecting the VisuMax laser platform costs and the specialized training required. As with LASIK, look for centers that include pre-operative evaluation, all follow-up visits, and enhancement guarantees in the quoted price. See vision correction cost guide.