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New laser refractive treatment

JUST about six years ago, patients who wanted to correct their eyesight with laser refractive treatment had only two procedures to choose from. The first generation laser treatment was Surface Ablation (or PRK, for photore-fractive keratectomy) and the second, Lasik, which stands for Laser-Assisted in-Situ Keratomileusis. Now, the latest laser refractive eye treatment, ReLEx-Smile (small incision lenticule extraction), is available in Singapore. It takes the best of the two procedures and is less invasive.

First, a brief overview of the two earlier treatments: In PRK, where the surface of the cornea is scraped off so that the laser can be used to reshape the cornea, the problem is the downtime – almost a week – for the cornea to heal and the patient to return to normal daily activity.

In Lasik, a 22-mm 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 three 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, which in 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.” explains Atlas Eye Specialist Centre’s Dr David Chan.

Although Lasik was very popular in the 2000’s because of its shorter downtime, doctors have now realised that it’s not suit-able for everyone – such as those whose corneas are too thin or shaped a certain way. “Cornea ectasia is a concern with all lasik -Smile is suitable for individuals aged 18 years and above with myopia and astigmatism. The surgery is less invasive and relatively painless.  Supervision procedures, particularly Lasik as it cuts the collagen fibres when creating the flap and patients with a preexisting condition, such as cornea ectasia, might see their corneas losing their intended shape over time as they are weakened by the Lasik treatment,” he adds.

The main advantage of Lasik is the fast-er healing time but the downsides are a large wound, potential for dry eyes and corneal weakening. When doctors learnt of this, there was a shift backwards towards Surface Ablation which is safer in the long run al-though it has a longer healing time and is associated with more pain and discomfort. In the latest-generation treatment, Smile, which is suitable for individuals aged 18 years and above with myopia and astigmatism, the surgery 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 sidecut. “The surface of the cornea is largely kept intact except for the small sidecut so there’s no risk of flap dislodgement. Be-cause there’s no flap, the cornea is also left stronger as well So it has the benefits of PRK in preserving corneal structural in-tegrity and similar comfort and speed of recovery of Lasik,” Dr David Chan explains.

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,” he said. The short laser time (24 seconds) and surgery time 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 cuts down dry eye conditions as fewer nerves are damaged.

In addition to this, Dr Chan also combines Smile with a Collagen Crosslinking treatment to further strengthen the cornea and reduce the risk of cornea 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 one minute immediately after the Smile procedure. When Dr Chan started his practice, he decided to bring in the Smile procedure to Singapore because of its advantages over the first two generations of treatments. Atlas Eye is the first and only independently owned eye specialist medical practice in Singapore offering ReLEx-Smile. Dr Chan completed the first combined Smile-Collagen Cross linking treatment for a patient in Singapore last week. The cost for Smile is just under S$5,000 for both eyes while Lasik is about 5$4,000.

“Patients now have three options for la-ser 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,” he concludes. Dr Lee Hung Ming of Lee Hung Ming Eye Centre (formerly Parkway Eye Cen-tre), however, cautions that Smile does not have an active cyclo rotation tracking system unlike the excimer laser which can follow the eye when it is rotating. “Because of that, it may not be ideal for treating astigmatism accurately. The other disadvantage is that visual recovery takes a bit longer than Lasily” he adds.

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