Eye specialists tell us about the side effects of this surgery to correct myopia. By Sasha Gonzales

Lasik is the most frequently performed procedure to correct myopia and astigmatism. Photo: Robert Przybysz / 123rf.com

Most of us know someone who’s had myopia-correcting surgery such as Laser-Assisted In Situ Keratomileusis, or Lasik for short. If you suffer from myopia (short-sightedness), you might be thinking of undergoing the procedure yourself.

Lasik is popular, not just in Singapore but all over the world. In fact, it’s 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. But it doesn’t come without risks and side effects – here’s what you need to know.

WHAT IT INVOLVES

Myopia-correcting surgery is also known as refractive surgery. According to Dr Christopher Khng, consultant ophthalmologist and medical director of Eyewise Vision Clinic, the procedure can be performed in two ways: On the cornea – both Lasik and PRK (photorefractive keratectomy) are carried out this way; or by implanting a corrective lens, known as ICL or implantable collamer lens surgery.   

“In Lasik, a corneal flap is created using an automated blade or a laser,” Dr Khng explains. “This corneal tissue flap is temporarily lifted out of the way, and the degree correction required is lasered onto the remaining corneal bed.

“This reshapes the cornea so that the eye has the desired degree correction. The corneal flap is then put back into place. The procedure is painless and takes between 10 and 15 minutes,” he adds.

Contrary to popular belief, presbyopia (or “lau hua”) does not occur any earlier in people who were 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 slightly, about +0.50 instead of 0 degree, then the lau hua may appear to start earlier, perhaps by one to two years.

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COMMON SIDE EFFECTS 

Myopia-correcting surgery promises perfect vision. But before you undergo the procedure, it’s important to know that not all patients share the same positive experience.

Lasik has a multitude of potential side effects – eye dryness is one of them. Dr Khng says this is 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.”

He adds: “Patients who have pre-existing dry eyes, especially those who are dependent on artificial tear eye-drops 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 halos. An additional risk factor is a large pupil size. These patients are more likely to experience starbursts and halos.”

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WHAT YOU PROBABLY DIDN’T KNOW ABOUT

If you’re considering Lasik, there are several other, more major risks to bear in mind.

1. Thinning of the cornea 

In some patients, Lasik can cause a problem known as post-Lasik ectasia. This is 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 to a greater extent.

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.

2. 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 where you would otherwise not need to wear spectacles after cataract surgery, you would now need glasses to see well.  

3. Risk of inaccurate eye pressure readings

If you’re diagnosed with glaucoma in later years, you’ll need to go for follow-up checks for eye pressure. Glaucoma is a condition where 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 a thinning of the cornea. Dr Khng says your doctor will have to apply this pressure adjustment, and this might lead to incorrectly low eye pressure readings.

4. Regression

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

5. 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 re-lift 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.

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6. Blindness

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

CHOOSING THE RIGHT DOCTOR

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, although these days, thanks to wave-front technology, that risk is reduced.” Wave-front technology evaluates the characteristics of your eyes, this 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, and right now, the technology used in the procedure is as advanced as it possibly can be. In fact, many eye doctors and other medical professionals have undergone the procedure themselves.

“But doctors need to select their Lasik patients carefully. If you do 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.

Our experts 

  • Dr Cordelia Chan, consultant eye surgeon at Eye Surgeons @ Novena / Ophthalmic Consultants, Mount Elizabeth Novena Specialist Centre
  • Dr Christopher Khng, consultant ophthalmologist and medical director, Eyewise Vision Clinic
  • Dr Mohamad Rosman, head and senior consultant, Refractive Surgery Department & Laser Vision Centre, Singapore National Eye Centre

This article first appeared on www.herworldplus.com.

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