JUST about 6 years ago, patients who wanted to correct their eyesight with laser refractive treatment had only 2 procedures to choose from. The 1st generation laser treatment was Surface Ablation (or PRK, for photorefractive keratectomy) and the second, LASIK, which stands for Laser-Assisted in-Situ Keratomileusis. Now, the 3rd generation, ReLEx® SMILE (SMall Incision Lenticule Extraction), is available in Singapore. It melds the qualities of both LASIK and PRK and is less invasive.
First, a brief overview of the 2 earlier treatments: During PRK, the surface of the cornea is scraped off so that the laser can be used to reshape the cornea. It takes longer, about a week, for the cornea to heal before patients can return to normal daily activities.
During LASIK, a 22mm circumferential cut (or side cut with a cleavage plane) is made to create a flap in the cornea, after which the laser is used to reshape the cornea. The downtime is about 3 days. However, the flap doesn’t reattach completely, so it is a potential weak link. In a small percentage of patients, there can be inflammation under the flap and even years later. If there is direct trauma to the eye, there is potential for the flap to shift or be dislodged. When the flap is made, it also cuts the nerves of the eye that are connected to the tear glands, therefore LASIK is associated with increased risk of dry eyes. The whole corneal integrity is also weakened to a greater degree in LASIK than Surface Ablation.
Although LASIK was very popular in the 2000’s because of its shorter downtime, doctors have now realised that it’s not suitable for everyone – such as those whose corneas are too thin or shaped in a certain way. “Corneal ectasia is a concern for post-LASIK patients. The main advantage of LASIK is the faster healing time but the downside are a larger incision, potential for dry eyes and corneal weakening. When doctors learnt of this, there was a shift towards Surface Ablation which is safer in the long run although it has a longer healing time and is associated with more discomfort.
ReLEx® SMILE is suitable for individuals aged 18 years and above with myopia and astigmatism. The procedure is less invasive and relatively painless. Only a small 2mm laser side cut is made on the cornea. The laser creates a small spherical membrane from underneath the corneal surface which is then removed through the small side cut. “The surface of the cornea is largely kept intact except for the small side cut so there’s no risk of flap dislodgement. Because of the absence of flap, the cornea is also left stronger. So SMILE has the benefits of PRK in preserving corneal structural integrity and LASIK with rapid vision recovery and minimal discomfort.
The removal of the spherical membrane is enough to change the shape of the cornea. The dimensions of the membrane will vary according to the prescription. But once it’s removed, the cornea’s curvature is changed in a very precise way and that would be sufficient to correct the patient’s prescription or refractive error. The laser time at 24 seconds is the same whether one has a low or high degree of myopia and that allows for more consistent results regardless of the level of refractive error corrected. The smaller incision also minimises dry eye conditions as fewer nerves are damaged.
In addition to this, ReLEx® SMILE can be combined with Collagen Cross Linking to further strengthen the cornea and reduce the risk of corneal ectasia. This is done by adding a few drops of a Vitamin B solution to the eye and shining ultraviolet light on the eye for 1 minute immediately after the SMILE procedure. The cost for SMILE is S$4,999 for both eyes while LASIK is about S$3,799.
Patients now have 3 options for laser vision correction, each with its own limitations and benefits. They should learn more about them and find out about what best suits their needs for today and the future.