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Laser Refractive Surgery

How does laser refractive surgery work?

The principle of laser refractive surgery is to sculpt or change the shape of the cornea (i.e. the transparent front surface or ‘window’ of the eye) in order to alter its refractive power as it is the cornea that does most of the refracting or bending of the incoming rays of light. This is with a view to enabling these rays of light to be focussed on the retina without the need for a refractive correction (i.e. spectacles and/or contact lenses). This is achieved by means of a computer-guided excimer laser along with sophisticated algorithms that together allow for a precise delivery of energy to the cornea in order to achieve the desired outcome.

Are there different types of laser refractive surgery?

There are two main types of laser refractive surgery. These are:

  • LASIK (Laser Assisted In Situ Keratomileusis)
    • Z-LASIK
    • iLASIK
  • Surface Ablation Techniques
    • PRK (Photorefractive Keratectomy)
    • LASEK (Laser Assisted Sub-Epithelial Keratectomy)


LASIK (Laser Assisted In Situ Keratomilieusis)

In this procedure, an instrument known as a microkeratome is used to create a thin flap in the cornea. This flap is then temporarily folded over and the computer-guided excimer laser applied in order to reshape the cornea. Once this is complete, the flap is folded back to assume its normal position again and begins to heal within hours. This is the most common type of laser refractive surgery and allows for fast visual rehabilitation.

There are variants of the standard LASIK procedure, examples of which include:


With Z-LASIK, a femtosecond laser is used to create the flap rather than a microkeratome. This laser applies millions of tiny laser spots in a row, one hundredth of a millimetre wide, in order to separate the tissue. This makes the procedure entirely blade-free.

  • iLASIK

This NASA-approved and blade-free variant combines the world’s most advanced measurement technology and computer-guided lasers into a safe and highly effective procedure that is completely tailored to the unique shape of each cornea.

Surface Ablation Techniques

Examples of surface ablation techniques include the following:

  • PRK (Photorefractive Keratectomy)

In this procedure, the thin outer layer of the cornea (referred to as the corneal epithelium) is removed completely and discarded. A computer-guided excimer laser is then used to reshape the underlying corneal tissue.  The corneal epithelium repairs itself within a few days of the procedure being completed but a protective contact lens will be required during this time.

  • LASEK (Laser Assisted Sub-Epithelial Keratectomy)

This is a variant of the above procedure in which the corneal epithelium is lifted away from the rest of the cornea using an instrument called a trephine. It is then preserved during the procedure before being placed back on to the cornea once the procedure is complete.

Although the visual rehabilitation with these surface ablation techniques is not as fast as with LASIK or its variants, the results tend to be the same. However, of the two approaches it is generally PRK that is favoured over LASEK. This is because it is quicker for a new corneal epithelium to grow (as in PRK) than it is for a replaced corneal epithelium to recover (as in LASEK).

What are the risks?

Although the majority of laser refractive surgery is carried out without any complications, it is important to recognise that, much like any surgical procedure, it is not risk-free.

Examples of potential risks to be aware of include:

  • Over-corrected/Under-corrected vision

This tends to apply more to PRK and/or LASEK

  • Visual aberrations (e.g. haloes, starbursts and/or double vision)

This tends to apply more to LASIK and/or its variants

  • Dry Eye Syndrome

This can apply to all types of laser refractive surgery

  • Infection

This can apply to all types of laser refractive surgery (but is very rare)

  • Corneal ectasia (i.e. the cornea bulging and thinning out)

This can apply to all types of laser refractive surgery (but is very rare)

The success of any of these procedures will depend on your refractive error (i.e. your spectacle prescription) but also on the competence of the surgeon carrying out the procedure. This is why it is of the utmost importance that, if you are considering laser refractive surgery, you do your research. This particularly applies with regards to the success rates of the clinics you are looking into and the specific procedure(s) you would be interested in.

And remember; make sure to take note of whether the person offering it to you is wearing spectacles themselves!

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