SMILE Eye Surgery — Laser Vision Correction Without a Flap

Laser vision correction is usually known through the two established methods, LASIK and PRK. But over the past decade a third method has come into use — SMILE — whose distinction is that it reshapes the cornea without creating a flap at all. This page explains what SMILE is, how it differs from the other two methods, and who it suits. For the full picture of LASIK and PRK, recovery and success rates, see laser vision correction.

How SMILE works

The name SMILE stands for Small Incision Lenticule Extraction. Instead of exposing the inside of the cornea, a femtosecond laser draws a lenticule within the thickness of the cornea — a thin disc of tissue whose shape is calculated precisely to the patient’s prescription. The surgeon removes the lenticule through a tiny incision at the edge, about 2 mm across. The removed tissue changes the curvature of the cornea exactly as in the other methods — but here it is done from within, without a flap and without removing the epithelial layer.

SMILE, LASIK and PRK — three routes to the same goal

The three methods share one principle — a precise change to the shape of the cornea — but they differ in how they reach the tissue being reshaped:

• LASIK creates a thin flap in the cornea, lifts it, reshapes the tissue beneath with a laser and replaces the flap. Recovery is very fast and almost painless.
• PRK removes the outer epithelial layer, reshapes the surface of the cornea, and lets the epithelium regrow within days. There is no flap, but recovery is slower and accompanied by discomfort.
• SMILE creates no flap and removes no epithelium: it extracts a lenticule from within the cornea through a tiny incision. In a sense it is the middle route — without the flap of LASIK and without the broad surface wound of PRK.

The advantages of SMILE

The absence of a flap is the source of most of the advantages:

• Corneal biomechanical stability. Because the peripheral fibre network of the cornea stays more intact, the cornea remains mechanically stronger. This is especially relevant to occupations or sports with a risk of direct eye trauma.
• Fewer flap-related complications. There is no flap that could shift, wrinkle or be injured by a later blow.
• Less dry eye after surgery. The small incision cuts fewer of the corneal nerves responsible for surface sensation and tear production, so the dryness after SMILE tends to be milder than after LASIK. On this phenomenon in detail, see dry eye after laser surgery.

The limitations worth knowing

• The treatment range. SMILE is approved for myopia and myopic astigmatism, but is not currently intended for farsightedness (hyperopia), which remains in the research domain.
• Slightly slower visual recovery. In the first days, vision after SMILE usually sharpens a little more slowly than after LASIK, even if the final result is similar.
• A different top-up. If further adjustment is needed, a flap cannot be lifted as in LASIK; it is usually done by a surface method (PRK).

Who is a candidate

As with all laser methods, the cornea decides, not the preference. Adequate corneal thickness, a regular shape on mapping, and a stable prescription over time are required. Within that framework, SMILE particularly appeals to those who want to avoid a flap: patients prone to dry eye, contact-sport athletes, and those whose work exposes them to eye trauma. The final choice between SMILE, LASIK and PRK is made after corneal mapping and a full preliminary examination, weighing the structure of the cornea, the size of the prescription and lifestyle.

On what determines the cost of each method, see the cost of laser eye surgery.

Bottom line

SMILE is the third method of laser vision correction, and the only one that works without a flap — an advantage that shows up in better corneal biomechanical stability and less dry eye, at the price of slightly slower recovery and a treatment range limited to myopia and astigmatism. It is not sweepingly “better” or “worse” than LASIK and PRK — it is an additional tool, and each patient has the method that suits their cornea. The way to know which is a preliminary examination, not a rule of thumb.

The information on this page is general and not a substitute for a personal examination and medical advice. Suitability for laser surgery, and the choice of method, are determined at a preliminary examination with an ophthalmologist.