Human normal eye visionRefractive laser vision surgery involves the use of an advanced laser system to reshape the focusing power of the cornea at the front of your eye. It is designed to reduce your need for glasses and contact lenses. The two most common forms of laser vision correction surgery are LASIK and PRK. The following diagrams illustrate an eye that has emmetropia (no refractive error), myopia (short sightedness) and hyperopia (long sightedness)


LASIK

LASIK (Laser-assisted in-situ keratomileusis) is a type a laser vision correction procedure to treat common refractive errors: short-sightedness (myopia), ongsightedness (hypermetropia) and astigmatism. It can also be used for “fine-tuning” after cataract surgery to get the best possible unaided vision. It is the most commonly performed procedure to treat refractive errors, particularly because visual recovery is rapid and discomfort is minimal.


LASIK involves essentially two steps. The first step is to create a very thin flap on the surface of the eye (cornea) that is then lifted back, so that a very accurate laser can reshape the underlying cornea to correct the refractive error. The flap is then carefully repositioned and then maintains its position by natural adhesion. No stitches are required.


We routinely perform LASIK using a femtosecond laser to create the flap at a predictable and precise depth. This results in what is known as “bladeless laser eye surgery”. This differs from traditional LASIK which used a cutting instrument known as a microkeratome to create the flap.

Myopia, vision disorderPRK (or ASLA)

Photorefractive keratectomy (PRK) is also known as Advanced Surface Laser Ablation (ASLA).

Unlike LASIK, there is no flap created in the front of the cornea. Instead of creating a flap, the surface cells (epithelial cells) are removed and the underlying corneal surface is then reshaped with the laser and covered with a bandage contact lens. The corneal surface (epithelium) then heals over the top of the treated area. The visual outcomes of surface ablation and LASIK are similar. Normally, however, the visual recovery after LASIK is faster, and discomfort after LASIK is usally lower.


normal eyePRK does have has a number of advantages. Because there is no corneal flap, surface ablation can be performed in some thin corneas that are not suitable for correction with LASIK. Also, surface ablation may be the preferred option in some people who engage in activities or occupations that are at high risk of producing trauma to a corneal flap, such as boxers. Surface ablation may also be a better option in some cases where corneal scarring can also be treated simultaneously. Like LASIK, surface ablation can also be customised to treat the minute optical imperfections of the eye.

Not all individuals are suitable for surface ablation, which requires a consultation and extensive investigative tests to determine suitability. Some patients may be better candidates for other refractive procedures.

Hyperopia, vision disorderLASIK can be customised to treat fine optical aberrations from an individual’s eye. This involves taking detailed measurements of the eye’s optical aberrations wavefront scans), which are used to program the laser. Custom LASIK (or wavefront-guided LASIK) is therefore individualised to treat each eye’s minute optical imperfections. LASIK is usually performed on both eyes on the same day, and takes about 30 minutes. Vision recovery is usually very rapid with little or no discomfort post operatively. Local anaesthesia in the form of drops is used prior to the procedure, as well as a mild oral sedative. You can usually return to work, and even drive within 24  hours after surgery. Not all individuals are suitable for LASIK, which requires a consultation and extensive investigative tests to determine suitability. Some patients may be better candidates for other refractive procedures.