How SMILE Works: A Lenticule, a Small Incision, No Flap

What a lenticule is

A lenticule is a piece of cornea shaped like a contact lens, made by the laser rather than moulded in a factory, and it exists for a few minutes before it is taken out. Its shape is the whole point: the amount of tissue it removes at the centre and towards the edge is what decides how much the cornea flattens and therefore how much short sightedness is corrected.

The cornea has layers, and the useful one for vision correction is the thick middle layer, the stroma. A lenticule is cut from within that layer, which is why the surface of the eye is never lifted: the laser creates two surfaces inside the cornea, one behind the lenticule and one in front of it, and they meet at a small opening at the edge.

Because a lenticule is a physical object with a defined thickness, the prescription is limited by how thick a disc can be created and removed while leaving enough cornea behind. That is the technical reason the technique is established for short sightedness and myopic astigmatism rather than for every prescription.

How the laser makes and removes it

1. 01

   The eye is docked under the laser

   A curved interface holds the eye steady against the laser while the treatment pattern is applied. This is the part most people notice: a sensation of pressure, and vision dimming for as long as the eye is held.

   What the procedure is like

2. 02

   The laser separates a lenticule inside the cornea

   Femtosecond pulses create a thin disc of tissue with a precise shape derived from your prescription. A second plane separates it from the tissue below, and a small opening is made at the surface at the same time.

   What a lenticule is

3. 03

   The surgeon removes it through a small incision

   The lenticule is freed and withdrawn by hand through an opening of a few millimetres. Nothing is cut away from the surface, and no flap is created at any point.

   Why the incision matters

4. 04

   The cornea closes and the refraction changes

   Removing the lenticule changes the curvature of the cornea, which is what corrects the focus. The incision closes without stitches, and the surface is left to settle on its own.

   The first days afterwards

The laser itself uses pulses measured in femtoseconds, each one a fraction of the energy that would damage tissue by heating. Instead of cutting, the pulses are focused at a chosen depth and create a microscopic separation by a process called photodisruption: gas and tissue are vaporised at a point, leaving a smooth plane behind. Thousands of these points, laid out in a spiral, become a surface.

The precision that matters is depth. The intended thickness of the remaining cornea beneath the lenticule is calculated before treatment, and the laser is programmed to stop at a defined plane rather than an approximate one. That is also why the preoperative measurement of corneal thickness is not a formality.

Why the small incision matters

The visible difference is that the eye has a short line near its edge rather than a flap that was folded back, and the practical differences follow from that. A flap cuts across a band of corneal nerves and creates an interface between tissue planes; a small incision interrupts far fewer nerves and leaves a much smaller surface at which two planes have to heal.

That is why reviews of tear film and surface measures after lenticule extraction tend to report a milder early dry-eye picture than after a flap procedure, and why the cornea's response to pressure and its biomechanics are studied differently in a flapless eye. It is also why there is nothing to displace later: a flap can move if the eye is rubbed hard in the first weeks, and a closed incision cannot.

SMILE and SMILE Pro: what the platform changes

SMILE Pro is not a different operation. It is the same lenticule extraction performed on a newer generation of the same manufacturer's laser platform, and the differences are in how the laser behaves rather than in what happens to the eye.

The newer platform applies its pulses faster, which shortens the time the eye spends held by the interface and allows the lenticule to be created in a different pattern. Studies comparing the generations report shorter suction times and comparable safety profiles rather than a different outcome for a given eye. What a patient feels is mainly that the uncomfortable part passes sooner.

This distinction matters commercially, because the word Pro is used in advertising as though it described a different product. If a clinic charges more for a newer platform, the honest question is what that money buys you in your own measurements, and whether the surgeon's experience is with the platform being quoted.

What it can and cannot correct

Lenticule extraction is established for short sightedness and for astigmatism of the kind that accompanies it. It is not established for long sightedness, where a flap-based procedure or a surface treatment is the realistic option, and the size of prescription it can treat is bounded by corneal thickness rather than by the marketing on the website.

Among the situations that rule it out or make it inadvisable are keratoconus and other irregular corneal shapes, a cornea too thin for the arithmetic to work, significant active eye disease, and a pregnancy or breastfeeding period, where the refraction is not stable enough to treat. Each of those is a decision made at an examination with imaging, not from a symptom list.

What you notice afterwards

Because the surface is not lifted, most people have usable vision within a day or two, with a scratchy rather than painful sensation and a visible line at the edge of the cornea that fades. Vision continues to fluctuate for weeks while the cornea and tear film settle, and dry eye in the early period is common after any refractive procedure.

The SMILE Pro recovery timeline goes week by week

Questions people ask about SMILE

Each question below opens the page that answers it in full, where the long version of the answer is. The direct answer is printed here so you can tell whether it is the question you are asking.

• Does SMILE leave a flap?

  No. SMILE creates no flap. A lenticule is shaped inside the cornea and removed through a small incision, so the surface of the eye is not lifted as it is in LASIK.

• Who cannot have SMILE?

  SMILE is generally not used where the prescription falls outside the range the technique can address, where the cornea is unstable or irregular, or where the ocular surface is too dry to measure and heal reliably.

• Can SMILE treat high short sightedness?

  SMILE is used at higher short sighted prescriptions than some older surface techniques, but what can be treated still depends on the cornea rather than on the prescription alone.

• Should I ask how many procedures my surgeon has performed?

  Yes, and it is a reasonable question to ask directly. Surgical experience is one of the few things about a clinic that a patient can actually check, alongside licensing and what the quoted price covers.

• Which procedure is suitable if I have dry eyes?

  All of the corneal procedures can affect the tear film, and the honest answer is that dryness is assessed and treated before any of them is planned. Where dryness is significant, a lens-based option may be discussed instead.