The excimer laser can remove corneal tissue in a controlled manner not possible with conventional ocular microsurgery. By reshaping the cornea, the excimer laser can correct short-sight, long-sight and astigmatism. The reshaped corneal surface allows images to be focused on the retina. Technical progress with this technology, which has now been used for over 25 years, has been rapid, improving safety and outcomes. Excimer laser treatment can be carried out in two different ways.
Laser Assisted Epithelial Keratomileusis (LASEK)
LASEK is a variant of Photo Refractive Keratectomy (PRK). Instead of rubbing off the surface epithelial cells prior to lasering the corneal surface, the epithelial cells are lifted as an intact layer. After the laser treatment is complete, the epithelial cell layer is replaced and protected with a contact lens for up to five days. This usually helps to reduce postoperative discomfort and quicken visual recovery.
The actual laser procedure is short, painless and only requires topical anaesthetic (eye drops). The patient’s refraction is programmed into the laser computer which calculates how much of the corneal surface to remove to correct the refractive error (this is usually less than 10-20% of the corneal thickness and the physical strength of the eye is essentially unchanged).
TransPRK / SmartSurfACE
With the SCHWIND AMARIS laser it is possible to carry out no-touch, all-laser surface ablations. TransPRK (Transepithelial Photorefractive Keratectomy) is an advanced version of surface treatments such as LASEK, Epi-LASIK and PRK. The epithelium, which is the regenerative surface of the eye, is ablated by the laser system. TransPRK is a transepithelial single-step treatment that avoids the eye coming into contact with any instrument. SmartSurfACE is an innovative eye laser surgery method that combines the benefits of touch-free TransPRK surface treatment with SmartPulse technology to give an impressively smooth corneal surface. Healing is typically 2 days faster than with earlier surface laser treatments such as LASEK.
Laser In-situ Keratomileusis (LASIK)
Whilst surface ablation is highly accurate in correcting low refractive errors, the results can be less predictable with the higher degrees of refractive error. In these patients LASIK is the preferred procedure. LASIK also accurately corrects low refractive errors.
The technique falls into two distinct steps, the creation of a corneal flap and the subsequent lasering of the corneal bed. Instead of lasering the surface layers, a superficial, thin, hinged flap of corneal tissue is made. This flap is then lifted and the laser is applied to the deeper corneal stromal bed before the flap is repositioned. The eye has a naturally occurring suction capacity, which holds the flap secure when the procedure is completed, therefore no sutures are necessary.
As with surface treatments, this is a painless procedure.
LASIK or Surface Ablation?
The LASIK procedure can provide several advantages over surface treatments:
Less postoperative discomfort – as the corneal surface is only slightly disturbed it is rare for the LASIK patient to experience discomfort. Minimal irritation is expected initially for a few hours. With surface treatments it takes upto five days for the surface epithelial layer to regenerate and some discomfort and possible pain is likely in this time.
Faster visual recovery – as the epithelium is only minimally disturbed during LASIK the recovery is usually very fast with the majority of patients having a good level of unaided vision by the next day. Useful vision in surface treatment occurs only when the epithelium has regenerated and vision may take a little longer to become clear.
Lower incidence of corneal haze and scarring with LASIK – corneal haze is a potential side effect of surface treatment, particularly with higher refractive errors. Haze can cause or exacerbate symptoms such as glare and haloes, and contribute to myopic regression. LASIK allows surgeons to approach higher errors with greater confidence in relation to the end refractive result.
Faster stability – less fluctuation through the healing process (i.e. regression) and decreased corneal haze or scarring offers a faster and more stable correction with LASIK.
Both LASIK and surface treatments have associated risks and complications. See the ‘Risks and Complications’ section.