How Does Laser Eye Surgery Work?

Laser eye surgery uses a beam of ultraviolet light to reshape your cornea

Any operation that corrects the focusing of the eye is called refractive surgery.

Laser eye surgery is simply a form of refractive surgery that uses a laser to reshape your cornea – the transparent, curved window at the front of the eye.

Adjusting the curvature of your cornea allows light to be focused correctly onto the retina at the back of the eye. Refractive surgery is the world’s most common elective surgical procedure.

The most popular form of laser eye surgery is LASIK (laser in-situ keratomileusis).

During LASIK, the surgeon uses either a femtosecond laser or, rarely, a mechanical device called a microkeratome to create a very thin corneal flap, about a tenth of a millimetre thick.

The surgeon then lifts this corneal flap and uses a second (excimer) laser to sculpt the bed of the cornea.

This procedure can be used to flatten the cornea (to correct short-sightedness), make it steeper (to correct long-sightedness), and make it more symmetrical (to correct astigmatism).

When the surgeon puts the corneal flap back, the cornea takes on this new shape.

ReLEx SMILE is a keyhole form of LASIK laser eye surgery.

SMILE (which stands for small incision lenticule extraction) differs from LASIK in that the surgeon does not need to create a flap in the cornea. Instead, a femtosecond laser is used to create a tiny tunnel, through which the surgeon draws out a minuscule amount of corneal tissue (less than 1/100th of the width of a human hair).

The main advantage of SMILE over other forms of laser eye surgery is that it is even less invasive than LASIK, as no flap is created. SMILE can be used to treat even higher prescriptions than was previously deemed possible and is often a preferred option for patients with drier eyes or thinner corneas.

With LASIK and SMILE laser eye surgery, the healing process is surprisingly short.

In almost all patients, the flap (in LASIK) or the tiny tunnel (in SMILE) heals within a matter of hours after surgery. Anaesthetic drops are used to numb the eyes during surgery, so the procedure itself is totally painless.

It is normal to experience a small amount of discomfort on the evening after surgery as the anaesthetic wears off, but this is rarely troublesome and painkillers are provided for use if necessary.

Most patients notice a significant vision improvement immediately after surgery, and vision continues to improve over the next 24 – 48 hours.

The rapid visual recovery time means that the vast majority of patients can return to work within 24 hours of surgery, although it will take about 3 months before the final visual outcome will be realised.

For the small minority of patients who are unsuitable for either LASIK or SMILE laser eye surgery, there are alternative ‘surface’ procedures known as PRK (photorefractive keratectomy), LASEK (laser sub-epithelial keratomileusis) and Epi-LASIK (epithelial laser in-situ keratomileusis).

These procedures all involve removing the surface layer of the cornea (the epithelium), and then treating the exposed area underneath with a laser. To the patient, the main difference between LASIK or SMILE and these surface procedures is the healing time. After a surface procedure, it takes approximately 5 – 7 days for the eyes to heal, and for vision to stabilise.