Some people with high myopia, myself included, have put off having their eyes lasik-ed in the past, because the understanding was that it's difficult to fully correct high myopia.

But with lasik technology getting more advanced, and with more centres touting the wonders of 'blade-less' or 'blade-free' lasik - also known as femtosecond lasik - for instance, the procedure is beginning to sound more promising to the highly myopic population. Or is it?

With all the different kinds of lasik out there, how does one decide whether to go bladeless or not? Or, in proper medical-speak, should one go for femtosecond lasik, or microkeratome?

That seems to be the main debate these days. So I talked to two doctors in private practice, and two in public hospitals, to find out what advice they'd give to a person with high myopia who has short-sightedness of more than 500 degrees in each eye.

The first doctor on my list was Lee Hung Ming, senior consultant ophthalmologist and medical director of Parkway Eye Centre. 'There are two parts to lasik,' he explains. The first is the cutting of the flap, which is a very critical step; and part two is lifting the flap to do the laser treatment on the cornea.

'People tend to think that lasik is just an all-laser procedure but not with the microkeratome. Today, it can be an all-laser treatment though, with femtosecond lasers,' says Dr Lee. He uses IntraLase, which he believes is the best femtosecond laser machine available today.

'IntraLase has several advantages over the conventional procedure which uses a blade. First, it's safe; with the ministry of health's 2005 data showing no adverse incidents or any flap complications at all that year. Compared to 99.5 per cent on average safety rate for the microkeratome (blade) cut.

'Using the IntraLase for flap creation is more predictable and more precise; and more importantly, the cut is very smooth, so it translates to better vision in the day and at night. It's the flap which gives rise to fast visual recovery,' says Dr Lee.

Once the flap is created and lifted, then the cornea will be re-shaped with the laser. The higher the degree, more cornea will need to be taken away; which is why some people can't have lasik because their cornea isn't thick enough to begin with, explains Dr Lee.

The other advantage of IntraLase is that it creates a 100 micron-thick flap, as opposed to 110 to 160 microns for the conventional blade, he points out.

From the ardent IntraLase advocate, I hopped over to see Jon Goh, senior ophthalmic consultant surgeon, at the Lasik Surgery Clinic in Paragon Medical Centre.

Dr Goh's approach was to calculate the amount of cornea you've left after lasik. The patient's suitability for lasik is ascertained from the Orbscan, which scans the thickness and steepness of your cornea.

Doctors have a chart that works out the calculations for them. Say I had 1,000 degrees short-sightedness in one eye, for instance, they can tell me that the laser treatment will take away 122 microns.

'If your corneal thickness is 500 microns, then it's 500 minus 232 (122 microns plus 110 microns for the flap), leaving 268 microns, which means the patient can consider lasik.

'The minimum total thickness of the cornea must be 360 microns, taking into account the 110 micron-thick flap to be created. As long as we get a residual corneal bed of 250 microns, then we're good to go.'

Different centres use different microkeratomes, and at The Lasik Surgery Clinic, they use the Moria microkeratome which is a 110 micron blade.

'IntraLase is a minimum of 100 microns, so it's a difference of 10 microns. One shouldn't go below 100 microns, otherwise you will get problems with the flap.' The Lasik Surgery Clinic is about to get an IntraLase machine soon, as the trend is moving there because of potential market demand, says Dr Goh.

'There are pros and cons to the use of femtosecond lasers for flap creation. One large negative is the extra expense to the patient. Studies have shown that although femtosecond laser flaps hasten visual recovery and provide better quality of vision in the initial period after surgery, compared to a microkeratome flap, the final outcome at three months evens out between the two.'

It means patients will have to pay more for femtosecond lasik, but if the cornea is thick enough, they may not need femtosecond lasik.

However, there will be a segment of the population who would demand the best and the latest in technology, and acquiring the IntraLase is a means to cater to that niche segment, he says.

For those with thin corneas - less than 250 microns of residual corneal bed - epilasik (which is a more painful procedure) is recommended. But not for those with a high degree of short-sightedness, because one can get corneal haze.

Full or partial correction

Clinical associate professor Heng Wee Jin, head of the Tan Tock Seng Hospital (TTSH) LASIK Centre and senior consultant, points out that the first criteria - if deciding to go for lasik - is the thickness of the cornea. 'The minimum guideline is a total thickness of 470 to 500 microns.'

After that criteria is satisfied, one should look at the ability to get a full correction, he says. 'For those with high myopia, say more than 1,000 degrees, sometimes only partial correction can be done if the cornea does not have sufficient thickness; whereas for lower myopia, full correction is usually not a problem.'

The femtosecond laser is supposed to be safer, with fewer complications during the flap creation, and visual quality is usually better, he agrees. 'The flap with the IntraLase sits better. On the other hand, flaps created using the blade can occasionally slip sideways. Also, flaps cut with the laser tend to heal faster,' says Assoc Prof Heng.

'But more importantly, the femtosecond laser can cut a thinner flap, leaving a thicker corneal bed with more room for laser treatment. So this is better news for someone suffering from high myopia.' TTSH has had the IntraLase machine for the last three years, and has treated more than 3,000 cases, he said.

Then, when it comes to correcting power, 'There are different softwares available to treat the cornea. From standard lasik to customised lasik. There's wavefront, aspheric, tissue-saving, and presbyopic lasiks nowadays, depending on the characteristics of the eyes.'

Wavefront addresses minute optical aberrations present in eyes by smoothening out irregularities. 'Although now we find that the difference is usually minute, and that it can sometimes be negligible,' he says. The effects of aspheric lasik - a treatment algorithm that attempts to recreate the aspheric surface of our natural cornea - is also rather negligible, he notes. Both take away more tissue.

The real improvement over standard lasik, he feels, is tissue-saving lasik. 'This is typically used to correct short-sightedness of more than 600 degrees while taking away less tissue compared to standard lasik,' he says. The other advantage is that treatment time is shorter.

Used in combination with IntraLase that cuts a thinner corneal flap, treatment of high myopia cases which were previously not possible can now be achieved. Tissue-saving lasik costs about $200 more than standard lasik, although again, if a patient's cornea is thick enough, they don't need it.

Technology or surgeon

To Chan Wing Kwong, Singapore National Eye Centre's (SNEC) senior consultant and head of refractive surgery, the surgeon is as critical as the technology, and his experience is paramount. 'As surgeons, we've to find a combination of techniques to give patients the best possible outcome in the safest possible way,' he says.

Price aside, you really want the best surgeon to treat your only pair of eyes. 'Equipment and technology is important in lasik, but it's still a medical procedure. So the doctor's experience is important. You could compare it to a jet plane. You can have the most advanced airplane, but that doesn't mean you don't need an experienced pilot to fly it.'

And the truth is that high myopia remains a difficult case for treatment, according to the Singapore National Eye Centre's statistics. 'High myopia tends to be more difficult. It's harder to get 6/6 or 20/20 eyesight. This lies in the experience of the doctor,' he says. 'Femtosecond lasik doesn't make something undo-able, do-able.'

Femtosecond lasik can make a reasonably safe, predictable, good and thin flap, but equally important is the treatment algorithm the surgeon chooses to treat the cornea. 'It's the surgeon's judgement call as there are many variables, and different kinds of algorithms out there for lasik treatment,' Dr Chan says. SNEC has the Femtech machine, and not IntraLase.

He says that generally, in femtosecond lasers, the standard deviation veers towards creating thicker flaps than its supposed 110 microns, while microkeratomes can create thinner flaps than their purported 120 microns.

'In the July issue of the Ophthalmology journal, researchers in the US have noted that the femtosecond and microkeratome methods of flap creation didn't affect visual outcome,' says Dr Chan. 'It's a toss-up at the moment, while the cost of femtosecond lasik is significant higher, by $500 to $1,000,' he notes.

Meanwhile, for very high myopia (more than 1,000 degrees), the chances of getting 6/6 vision are about 40 per cent; while chances of getting 6/12 - within 100 degrees - are 85-90 per cent.

That's the average result seen at the national eye centre. 'There are patients who do extremely well, of course, but those are the average results we see,' says Dr Chan.

SNEC has a femtosecond laser (Femtech), but uses it only in selected cases. 'We find that the microkeratome offers a safe and cost-effective outcome for the patient,' he adds. SNEC uses the Zyoptix XP microkeratome.

What I decided, after these various consultations, is that coming to a conclusion is easier said than done. But it's still best to be somewhat clear on the issue, when choosing an elective treatment.