How do lasers work on eyes?

The first laser sculpting process for eyes was used more than 35 years ago, and these days the phenomenal technological advances in the field of eye surgery have really seen the use of lasers skyrocket. How do they work?

What lets a laser cut tissue

Lasers cut cleanly through tissue by using specific light wavelengths and pulse duration, so different types of laser are used for different procedures. Laser Eye Surgery uses a shorter wavelength, and sculpts the cornea to improve sight problems, usually myopia (short-sightedness), hypermetropia (long sightedness) and astigmatism (uneven curvature of the eye's surface).

The cornea and what surgery changes

The cornea is the transparent tissue that covers the front of the eye that helps to control focusing. During laser eye surgery, a computer-controlled Excimer laser is used to remove microscopic amounts of tissue from the cornea. The aim is to restore normal eyesight, without the need for glasses or contact lenses.

Creating the corneal flap

The bladeless LASIK procedure involves taking a thin flap of corneal tissue, created with another laser known as a femtosecond laser, and lifts the flap out of the way. The most widely used one is known as the IntraLase.

The way the flap is made is through infrared laser energy that inserts a precise pattern of tiny, overlapping spaces just below the corneal surface. This femtosecond laser operates at extremely high speeds (pulses of one quadrillionth of a second). This allows the tissue to be targeted and actually divides it at a molecular level, without heat or impact to surrounding tissue.

Reshaping with the excimer laser

The Excimer laser then reshapes the underlying tissue; it’s a ‘cool’ type of laser. It doesn’t burn tissue, but vaporises small amounts of the cornea every time a beam of the laser is pulsed onto the surface of the eye.

The diameter of the laser beam and the number of pulses that are directed onto the cornea are carefully controlled using computer technology, so that the surface of the cornea is reshaped.

Closing the flap and recovering

The flap is then put back over the eye to cover the newly recontoured surface. Recovery is swift, and anaesthetic drops mean most patients feel no pain during the procedure itself.