The Low-down On Lasik

Most of us know someone who’s had myopia-correcting surgery such as laser-assisted in situ keratomileusis – or Lasik for short. If you have myopia (short-sightedness), you might be thinking of undergoing the procedure yourself.

Lasik is the most frequently performed procedure to correct myopia as well as astigmatism, says Dr Cordelia Chan, consultant eye surgeon at Eye Surgeons @ Novena / Ophthalmic Consultants.

However, it is not without risks and side effects.

Myopia-correcting surgery is also known as refractive surgery. According to Dr Christopher Khng, consultant ophthalmologist and medical director of Eyewise Vision Clinic, it can be done in one of two ways: Lasik or PRK (photorefractive keratectomy) is carried out on the cornea. Alternatively, ICL (implantable collamer lens) is done to implant corrective lenses.

“In Lasik, a corneal flap is created with an automated blade or a laser,” Dr Khng elaborates. “Then it is lifted out of the way, and the degree correction is lasered onto the remaining corneal bed. This reshapes the cornea so the eye has the desired degree correction. The flap is then put back into place. The procedure is painless and takes 10 to 15 minutes.”

Contrary to popular belief, presbyopia, or “lau hua” in colloquial Chinese, doesn’t occur any earlier in people rendered with no degree by Lasik than in those who grew up with perfect eyesight and no degree, says Dr Khng. Of course, if the surgeon has over-corrected your degree, say by about +0. 50 instead of 0 degree, then the lau hua may appear to start earlier, perhaps by one to two years.

Surgery to correct myopia promises perfect vision, but before you do the procedure, you should know that not all patients share the same positive experience.

Lasik has a multitude of potential side effects, like eye dryness due to the creation of the corneal flap and the effect of the laser on the cornea. “Corneal nerves, which are important in natural tear production, are cut during the creation of the corneal flap. This often leads to dry eyes in Lasik patients,” explains Dr Khng.

He adds: “Patients with pre-existing dry eyes, especially those dependent on lubricant eye drops, also known as artificial tears, to achieve comfort, are particularly at risk.” Fortunately, the problem usually doesn’t last more than one to three months.

Seeing halos and starbursts is also common. “Like dry eyes, halos are the effect of the laser on the cornea,” says Dr Khng. “Patients with high myopia, or those with relatively higher amounts of astigmatism, are more likely to see starbursts and halos. An additional risk factor is a large pupil size.”

If you’re considering Lasik, here are major risk factors to note.

Thinning Of The Cornea In some patients, Lasik can cause a problem known as post-Lasik ectasia, where the cornea becomes irregular and unstable, resembling an eye disease called keratoconus.

Dr Khng says this tends to be more common in patients with a high myopic degree. The laser has to remove a lot of the cornea to achieve the required correction, thus thinning the cornea even more than usual.

However, Dr Chan adds that post-Lasik ectasia is rare, with the global incidence of cases at a mere 0.04 to 0.06 per cent.

Problems With Cataract Surgery In The Future In cataract surgery, the lens inside your eye is replaced with an artificial lens to restore clear vision. “As the patient’s corneas are permanently changed by Lasik, the lens calculations become difficult when a patient needs cataract surgery later in life,” says Dr Khng. “This is because the lens calculation formulas require a normal cornea for a correct reading.”

What this means is that you would need glasses to see well now.

Risk Of Inaccurate Eye Pressure Readings If you’re diagnosed with glaucoma in your later years, you’ll need to do followup checks on eye pressure. In glaucoma, there’s increased pressure on the eyeball. The disease causes damage to the optic nerve and leads to worsening eyesight and even blindness. Your eye pressure readings may be more troublesome because Lasik leads to thinning of the cornea. Dr Khng says your doctor will have to apply this pressure adjustment, and this might lead to incorrect low eye pressure readings.

Regression There is a chance that your old degree will come back again, says Dr Chan, especially in highly myopic patients. Usually, surgeons will over-correct slightly to account for this.

Uncommon Complications Related To The Lasik Flap Corneal flaps can become wrinkled or damaged, or even tear off during Lasik surgery, says Dr Khng. Even in the best- case scenario, the flaps never strongly adhere to the corneal bed after healing. This makes it easy for your doctor to relift the flap if he needs to perform corrective or enhancement surgery to get rid of any myopia that comes back later. But this means that the flap is vulnerable to injury, and prone to being dislodged as a result of trauma – such as being poked in the eye with a finger during sports, or being hit by a tennis ball.

Blindness In very rare cases, infection in the flap can lead to blindness.

Dr Mohamad Rosman, head and senior consultant of the Refractive Surgery Department & Laser Vision Centre at the Singapore National Eye Centre, says certain people are more at risk than others when it comes to experiencing problems after myopia-correcting procedures like Lasik.

“If you have a pre-existing dry eye condition, then you’re more likely to experience dry eyes,” he explains. “If you are highly myopic, then you may have problems with night vision. However, thanks to wavefront technology, that risk is reduced.”

Wave-front technology, he adds, evaluates the characteristics of your eyes, thus allowing for a more precise procedure.

Myopia-correcting surgery has a long track record of safety, but one way to minimise your risk of experiencing side effects and complications is to make sure you find a reputable doctor.

Says Dr Chan: “Lasik is effective and safe. The technology used in the procedure now is as advanced as it possibly can be. In fact, many eye doctors and other medical professionals have undergone the procedure themselves. However, doctors need to select their Lasik patients carefully. If you encounter problems after your surgery, then there’s a high chance that you might not have been suitable for it in the first place,” she adds. SH