Smile for clear vision

Fitness coach Fay Hokulani, 27, wore contact lenses for more than a decade, sometimes up to 15 hours at a stretch.

From time to time, irritants such as dust would get into her eyes when she conducted training sessions outdoors. She had to either excuse herself to remove and wash her lenses or bear with the discomfort until the end of the session.

Despite the hassle, she simply could not do without them. Her refractive error was a high -7.25 dioptres (commonly known as 725 degrees) and -5.50 dioptres in her right and left eye respectively.

Besides myopia, she also had mild astigmatism of -1.00 dioptres, which occurs when the shape of the eye's curvature is irregular.

Spectacles were not useful for her job, she said, as they would slip down her nose when she perspired. Last month, she underwent a relatively new procedure known as Relex Smile, which stands for refractive lenticule extraction, small incision lenticule extraction, to be free of visual aids for good.

In this technique, a small piece of corneal tissue is cut with laser and removed through a tiny incision.

It is a variation of refractive lenticule extraction, which has the European Union's CE Mark, but has yet to be approved by the United States Food and Drug Administration.

QUEST FOR PERFECT VISION

Ms Hokulani is one of close to 50 patients at the Singapore Medical Group's (SMG) The Lasik Surgery Clinic to have undergone the procedure in the last three months.

A day after the surgery, she was able to read the second last line on the eye chart, which had the second smallest font for its text. A week and a month later, she could read the last line, a testament to her new-found perfect vision.

The Singapore National Eye Centre (SNEC) is the only other medical institution here that offers Relex Smile to its patients. It has done so since February 2012.

Assistant Professor Mohamad Rosman, head of its refractive surgery service and Laser Vision Centre at SNEC, said about 5 per cent of the 2,000 to 3,000 refractive eye procedures done at SNEC yearly is the Smile procedure.

Most patients still opt for Laser-assisted in-situ keratomileusis (Lasik) as it has a longer track record and is cheaper, he said.

At SNEC, one can expect to pay at least $4,682 for the Smile procedure, compared with $2,996 for bladeless Lasik.

People who are suitable for Lasik would likely be able to undergo Smile as well, say doctors.

However, unlike Lasik, Smile cannot treat myopia of more than -10.00 dioptres and hyperopia (long-sightedness).

Ms Hokulani said she was not keen on Lasik because her elder sister suffered post-operative discomfort from dry eyes when she had the surgery six years ago. This is a common problem patients experience after undergoing the procedure.

A critical step of the Lasik procedure is the creation of a thin flap on the top layer of the cornea - the transparent portion of the eye which lets light through.

This flap of about 20mm in diameter is created with either the mechanical microkeratome (a blade) or the femtosecond laser.

Once the flap is lifted, another machine known as the excimer laser vaporises the corneal tissue underneath to reshape the cornea and correct the vision.

Smile, on the other hand, uses only one laser for the entire procedure and requires no flap, which is believed to weaken the cornea's biomechanical strength.

Instead, the femtosecond laser is used to cut a small piece of corneal tissue, called a lenticule, as well as make an incision of no more than 4mm in the cornea through which the lenticule is removed.

THE GOOD AND THE BAD

A smaller cut means fewer corneal nerves are damaged during the treatment and, subsequently, dry eyes would be less of a problem after the surgery, said Dr Eugene Tay, a consultant ophthalmologist at SMG's The Lasik Surgery Clinic.

The absence of a flap also reduces the risk of optical aberrations (distortions), which can cause significant night vision problems such as glare, haze and haloes, he explained.

The patient does not risk having the flap displaced or dislodged too.

This is especially useful for people whose occupations put them at high risk of eye trauma, such as policemen or soldiers, said Prof Rosman. The same goes for people who play contact sports.

At SNEC, doctors first learn to remove the lenticule through a flap similar to that created in Lasik. They then learn to do the same thing through a small area of the flap, but without lifting the flap completely. This pseudo Smile procedure, as the eye centre calls it, provides the doctor an option to revert to an easier method if he needs to.

Early studies show promise. Last month, results of all three surgical techniques (femtosecond lenticule extraction, Smile and pseudo Smile) published in the Journal Of Cataract And Refractive Surgery showed that patients' vision were still holding up well 12 months later.

Another study in the same journal reported that people who had their vision corrected with the refractive lenticule extraction technique had better eyesight years later, compared to those who had Lasik. Their vision regressed by only 0.07 dioptres after five years. But the Lasik group's eyesight worsened by 0.63 to 0.97 dioptres six to seven years later.

Yet, doctors cannot repeat a Smile procedure on the same person to make any adjustments, or perform Lasik on eyes that had undergone Smile to make further corrections. The technology does not allow doctors to do so, said Dr Tay.

Advanced surface ablation would therefore be the only recourse if one is not satisfied with his vision after the Smile procedure. This involves removing the superficial surface of the cornea, followed by laser treatment.

LASIK AS GOLD STANDARD

Dr Jerry Tan, who performed the first Lasik surgery in South-east Asia in 1996, recognises the potential of the Smile procedure. But he thinks the new technology has a long way to go before it can rival Lasik, which took 25 years to reach its current stage.

Dr Tan, who has studied the Smile technique, believes that Lasik is still the gold standard in refractive eye surgery. Tens of thousands of people have undergone it since it was introduced here in 1996.

A drawback of Smile, he said, is that the laser cannot compensate for the rotation of the eye when the person is lying flat on his back, as a suction force is applied to hold the eyeball in place.

If the laser deviates more than 0.2mm from the initial correction - which is done with the patient seated down - or the eyeball rotates more than 2 degrees, there can be inaccuracies in vision correction.

Jerry Tan Eye Surgery at Camden Medical Centre has laser eye trackers which monitor eyeball movements in seven directions and compensate for microscopic eye movements during surgery.

Today's technology has also allowed Lasik flaps to be created with a dovetail design that wedges the flap edge in, reducing the risk of flap displacements, he said.

He recalled a former patient who lost her eyebrows and eyelashes after a gas explosion in her kitchen, but her Lasik flaps stayed firmly intact.

joanchew@sph.com.sg

This article was first published on Oct 30, 2014.
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