LASIK or SMILE: which should I choose?

Many people research this question for weeks before a consultation. They have watched videos and read forums, and have often already decided on SMILE, or on LASIK because a friend had it. The homework is useful. But the answer is always the same: your cornea decides, not your preference. Here is why.

How LASIK works

In LASIK, a thin, hinged flap is first created on the surface of the cornea. The flap is lifted, an excimer laser reshapes the corneal tissue underneath to correct your power, and the flap is laid back in place, where it settles without stitches. The whole procedure takes minutes per eye, done under anaesthetic drops.

LASIK has decades of results behind it, and it corrects a very wide range of powers including cylinder (astigmatism). Vision usually recovers within a day or two; this varies.

How SMILE works

SMILE takes a different route. Instead of a flap, a femtosecond laser creates a thin, precisely shaped disc of tissue called a lenticule inside the intact cornea. The surgeon then removes that lenticule through a small keyhole incision of a few millimetres at the edge. Removing the lenticule reshapes the cornea and corrects your power.

The key difference is what is not done: there is no flap. The outer layers of the cornea stay almost entirely intact, disturbed only at that small keyhole.

Recovery and dry eye: the real differences

Both are done under anaesthetic drops. In suitable eyes both usually give good unaided vision; neither can promise freedom from glasses. The differences are more subtle than the internet suggests.

Dry eye: creating a LASIK flap cuts more of the fine corneal nerves that drive tear production, so temporary dryness after LASIK is common for a few months. SMILE disturbs fewer of these nerves, and may cause less dryness in some eyes. Existing dry eye is treated first, before either procedure.

The flap question: a LASIK flap heals securely, but it remains a structural feature of the eye. For people in contact sports, martial arts, boxing, or physically rough occupations, the flapless nature of SMILE avoids the small risk of flap displacement from a direct blow. For an office-goer, this difference rarely matters.

Speed of visual recovery: LASIK is typically a little faster to crisp vision, often by the next day. SMILE vision is good early but can take a few days longer to sharpen fully. In suitable eyes, results are usually comparable once vision has settled.

Who tends to suit which

Broadly, and only broadly:

• Higher minus powers can often be treated with SMILE, which does not need a flap.
• LASIK covers a wider range overall, including higher cylinder and plus powers where SMILE has limits.
• Thin corneas may not safely allow either. Every laser procedure removes tissue, and there is a minimum safe thickness that must not be crossed, because crossing it risks weakening the cornea permanently. For thin or borderline corneas, an ICL, a lens implanted inside the eye that removes no corneal tissue, is often considered instead.
• Certain corneal shapes suggest early keratoconus, a weakening condition in which laser surgery must not be done at all. Detecting this is one of the most important jobs of the pre-operative scans. You can read more on the keratoconus page.

The main point

The choice between LASIK and SMILE is not like choosing between two phones. It is a medical decision made from measurements: your corneal thickness, its shape and strength on tomography, your exact power and its stability, your tear film, your pupil size, your age and your lifestyle.

That is why a detailed suitability assessment comes before any discussion of “which one.” Sometimes the tests say both are fine, and then your lifestyle gets a vote. Sometimes they clearly favour one. And sometimes they say neither, and the options are ICL, or simply glasses or contact lenses.

Keep an open mind until the scans are done, and let the measurements guide the decision. All of these procedures carry risks, which your surgeon will explain before you consent.