Mr Glenn Carp at London Vision Clinic

Today, the range of treatments available (often with varying names) across the many Laser Eye Surgery providers can make it challenging to know which one to choose and just what the differences are. But underneath this, the endless promotions and branding, the number of Laser Eye Surgery techniques are very few.

All Laser Eye Surgery techniques work by reshaping the permanent tissue, or stroma, that sits in the corneal bed. The one thing that differs is how they access this tissue.

In the 80s, the best way to do this was by either loosening the epithelium with an alcohol solution and moving it to one side, as in PRK, or completely removing it, as in LASEK.

LASEK: The original surface treatment

Laser eye surgery was first introduced in the 80s in the form of photorefractive keratectomy (PRK). In PRK, the epithelium (the layer of skin on top of the cornea) is removed either manually with a semi-blunt blade or by loosening it with alcohol. More recently, the laser itself has been used to remove the epithelium in a procedure referred to as trans-PRK (i.e. transepithelial – literally through the epithelium). The treatment area is left exposed at the end of the process, protected by a soft contact lens until the epithelium has covered the whole surface – which usually takes about 4-5 days. Due to the large area of missing epithelium, patients experience pain while the epithelium is growing back, so patients are given pain medication after PRK. Unfortunately, this also means that the vision is blurry until the cornea has fully healed, which can take up to 3 months for the epithelium to completely remodel.

Since then, PRK has been modified into other treatment modalities such as LASEK and Epi-LASIK. The main difference compared to PRK is that the epithelium is replaced over the treated area at the end of the procedure. The hypothesis was that this would reduce the pain and hasten the visual recovery. In LASEK, the epithelium is removed as for PRK but is carefully moved to one side so that it can be moved back into position. Epi-LASIK has a specific method of removing the epithelium using a device known as an epi-keratome to lift the epithelium in a single sheet. This is similar to a microkeratome used to create a LASIK flap (like a woodworker plane) but has a blunter blade. Only the epithelial layer is lifted rather than cutting into the stroma.

Despite these differences, all of these can be grouped under the term surface ablation – because they all involve performing the laser treatment on the surface of the stroma (the main body of the cornea underneath the epithelium) rather than deeper in the stroma under a flap as in LASIK. Also, scientific studies comparing the different treatment types are yet to find a significant difference in terms of pain, visual recovery, or outcomes.

LASIK: A new way to do things

Developed in the late 80s, LASIK, or laser-assisted in situ keratomileusis, revolutionised Laser Eye Surgery and introduced the microkeratome to the industry.

Whereas the epithelium posed as a wall surgeons needed to get around in the past, the microkeratome allowed them to create a doorway.

The instrument is used to cut a circular flap, about one-tenth of a millimetre in thickness, including the epithelium and some of the stroma. This flap is then lifted to expose the stromal bed underneath. The surgeon then removes a precise amount of tissue and the flap is replaced to its original position. As it’s only the edges that need to heal, the flap regains most of its structural integrity within just a few hours.

Due to its efficiency and less disruptive means of accessing the stroma, LASIK quickly became the most popular type of Laser Eye Surgery in the world.

Not only is the procedure quicker (taking less than 15 minutes to perform), but the recovery process is much shorter and more comfortable.

As soon as the procedure is finished, patients see immediate improvements in their vision and return to their normal routine as soon as the next day.

Whether you suffer from shortsightedness, longsightedness, presbyopia, or astigmatism, LASIK is the industry standard you will find in most clinics today. Surface ablation procedures are generally reserved for patients with thinner corneas where a full correction isn’t possible to perform safely as LASIK due to the additional depth of the flap. However, modern femtosecond lasers have enabled very thin flaps to be created, so LASIK can now be performed even in eyes with thin corneas. In addition, the emergence of SMILE, a keyhole form of LASIK, has provided another treatment option for eyes with thin corneas. At the London Vision Clinic, surface ablation is used only for patients with corneal dystrophies, such as anterior basement membrane dystrophy, as surface ablation acts as a therapeutic treatment for such conditions.

Can’t decide which is best or more appropriate for you? Don’t worry, that’s what we’re here for. If you’d like to know more about our treatment options or book a consultation at London Vision Clinic, call us at 020 7224 1005.