LASIK vs SMILE: compared, side by side

What actually differs

A flap is the whole distinction. Cutting and folding one interrupts a band of corneal nerves and leaves a structural interface that heals, but never quite re-bonds. Keeping the surface intact avoids both, at the cost of taking the tissue out through a much smaller opening, which is technically harder and requires the cornea to be thick enough for the lenticule and the remaining bed.

Neither approach changes the fundamental correction: both remove corneal tissue to flatten the curve, so both are irreversible, and both are planned from the same preoperative measurements.

The first days after each

Most people treated with either technique can see usefully within a day or two. With a flap there is often a foreign-body sensation while it settles, and the standard instruction not to rub the eye is about protecting the flap rather than about the wound inside it. With a small incision the eye usually feels scratchy rather than sore, and the visible mark of the procedure is a line at the edge of the cornea.

Vision fluctuates in the first weeks either way, and this is expected rather than a sign that something has gone wrong. The differences between the two in the first fortnight are smaller than the differences between two individual patients.

Dry eye, and being precise about it

Every refractive procedure disturbs the nerves that tell the eye to keep its surface wet, and every one of them is followed by a period of dryness in some patients. The clinical question is not whether dryness happens but how much and for how long, and on that the reviews are consistent in direction while leaving the size of the effect open: measures of tear film and surface staining tend to favour the small-incision technique early on, with the gap narrowing as the nerves recover.

That makes the flapless option worth discussing seriously if your tear film is already borderline, and it does not make it a treatment for dry eye. If the surface is significantly compromised, the more useful conversation is usually about whether to proceed at all, and with which technique.

If you ever need another treatment

This is where the flap is an advantage rather than a complication. If a small residual prescription remains, or short sightedness returns years later, a flap can often simply be lifted and the cornea re-treated, which is a short and familiar procedure. There is no flap to lift after lenticule extraction, so an enhancement usually means a surface treatment, with the recovery that implies.

Ask any clinic what proportion of their patients need an enhancement and what they charge for one. A clinic that can answer is describing a policy; one that cannot is describing a hope.

Prescriptions, and where each is established

LASIK has the longer and broader track record, including long sightedness, higher astigmatism and repeat treatments. Lenticule extraction was developed for short sightedness and myopic astigmatism, and that is where its evidence base sits. If your prescription is long-sighted, the choice is usually between LASIK and a surface treatment rather than with SMILE.

That is a statement about evidence rather than about quality, and it is the kind of thing a clinic marketing SMILE Pro has an incentive to blur. Ask which technique your own measurements suit, and ask what the alternative would be if the first one were unsuitable.

• Ask how many of each technique the surgeon performs in a month, not how many they have performed in total.
• Ask what they would choose for their own eye, and why, in terms of your measurements rather than your lifestyle.
• Ask what happens, and what it costs, if a refinement is needed later.