I had this interesting question recently from Kevin:

Hi Doctor, Would you please advise if “zlasik” is still better and newer technology compared to “ilasik with iFS Advanced Femtosecond Laser”?  Thanks

Hi Kevin, I prefer the Ziemer system (Z-LASIK). We have the brand new Ziemer LDV Crystal Line system, currently the only one in the UK, and it is a remarkable flap creation tool. It has a 33 times faster repetition rate than the latest iFS 150KHz model, with energy per pulse far lower, tighter energy focus and the shortest suction-on time. We can do both eyes safely and very accurately in around 6 minutes.

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Omar asked:

Good Afternoon Mr Allamby,
I’m considering getting some treatment on my eyes, but am very worried about the long-term effect cutting the cornea can have. As i get older and my eyesight deterioates. will the my eyesight be worse off than if i had just kept wearing glasses?

Omar, I think this is one of the most common worries that prospective candidates have when considering laser eye surgery be it LASIK or PRK. It is just over 20 years since we first performed PRK for short-sight, and just under 20 years for LASIK, so we have considerable experience of long-term results.

The long-term outcomes have been excellent to date. Regression is seen in the London PRK study in 1-2% of patients, with a partial return to myopia, but not as bad as the vision had been before without glasses.

Cutting the cornea (e.g. to create a flap or flap disc) has been around for decades. Lamellar cuts were made in the 50s, and the first mechanical keratome was first used in 1963. No long term problems were seen, except when too little thickness was left in the cornea. At my clinic, we use a high safety standard of leaving 300 microns in the corneal bed, after creating the flap with a femtosecond laser and using the excimer laser to reshape the cornea.

The main worry is in excessive weakening of the cornea. However, the incidence of bending of the cornea through weakness in post-LASIK patients is the same as the incidence of bending from a disease known as keratoconus (KC). So in normal LASIK where all the safety parameters are observed, we are not sure if LASIK actually contributes to corneal bending post-operatively.

The key here, as always, is rigorous screening pre-operatively and visiting a centre where you get sufficient time for your consultation. Some clinics do consultations in 30 minutes, or even less. Others (mine included) spend much longer. Focus consultations take at least 2 hours.

Choose carefully.

Sandor asked this question on Lasik flap healing:

Dear Dave,
Is it true that corneal flaps never heal completely after Intralasik? What is the chance of dislocation during the rest of the patients life?
Thank you in advance, Sandor

Sandor, it’s an important question. It is true that thicker (e.g. blade, keratome) flaps never fully heal. They can be surgically lifted many years after. However, thin flaps such as are created with femtosecond lasers (around 100-110 microns) appear to heal significantly more strongly.

The healing in the uppermost layers of the cornea is different from deeper down. Collagen fibres are more wavy and heal much better when cut with a thin flap. I have found a couple of patients where I have tried to lift femtosecond flaps, and they were fully bonded down and impossible to lift after a year post-op. This has never been the case with keratome blade cut flaps which I have always been able to lift, even many years later.

IntraLasik is just the brand name for flaps made with the Intralase American made femtosecond laser. Using the Swiss Ziemer laser it is called Z-LASIK.

The key question first is the depth at which a flap was cut. One of the major reasons why many clinics have invested in femtosecond lasers over the much cheaper keratomes (10x more expensive for a femtosecond) is being able to cut predictable accurate thin flaps, with their better healing.

If it was a thin flap, e.g from a femtosecond laser (Ziemer, Intralase, Visumax, Femtec), I expect the lifetime chance of dislocation will be zero.

Sally asked:

I am considering laser eye surgery but am prone to keloid scars. Would this be a problem?

My reply was:

Hi Sally
Keloid scarring should be no problem with LASIK laser eye surgery. I have done several patients with keloid and had excellent LASIK vision results. No problems with healing at all.
Best regards, Dave

Anne asked:

Hi Dave,
I’ve come across a lot of comments from lasik patients re: dry eyes. Many of these did not suffer with dry eyes prior to surgery. Can this become a long-term issue as many people say they are still experiencing dry eyes 6 months down the line? Also, is it something that can be avoided through the laser used and surgeon’s experience/ability? I know that you say patients do not experience TLS with the Ziemer laser, so can the same be said of dry eyes?
You mentioned in one of your previous replies that there was someone in the Cheshire area I could go to for a consultation (with a view to having surgery with Focus), please could I have their contact details?
Many thanks, Anne

Hi Anne,
A temporary reduction in tears following LASIK happens in all cases, although many are unaware of it. It happens because the superficial corneal nerves are cut during flap creation. The cornea becomes number and the nerves have to re-grow to supply the surface with normal sensation. This takes 3-6 months with a thin femtosecond flap, longer with a thicker blade flap.

The thinner the flap, the less distance to re-grow and so the sooner the cornea returns to normal. So having patients report still having dryness at 6 months is not unusual, especially if they had a thicker flap.

In some cases of ongoing dry eye, there can have been some pre-existing deficit in the tear film or tear quality that gets exacerbated by the temporary numbness in the cornea and other factors (e.g. loss of goblet cells).

I find ongoing dryness is rare in my clinic, and I think that is because we are rigorous in diagnosing, and treating where needed, prior to surgery. Technology cannot avoid the creation of some dryness (whether symptomatic or not). However creating a thin flap with a femtosecond laser makes for less dryness of shorter duration.

But it is the skill of the surgeon and clinical team that heads of problems before they are created, by not operating on patients who may lead to later trouble. Patients with marked dry eye should not have LASIK. Some dryness though can be managed and treated pre-op and so allow those patients to still be eligible for LASIK and without long-term problems.

Anne, call one of my team on 0845 5000 500 and we can connect you with our optometrist in Cheshire for an assessment.

Terry asked:

I am thinking of laser eye treatment. I have a squint in my left eye and long vision. The consultant has told me the squint and vision will be corrected by the surgery. I will be having wavefront laser. Can you tell me if this will work? My glasses correct the squint and my vision,

Terry, There are different causes for squints. The laser correction itself will only change the focus of your eyes, but as some squints are linked to focusing of your vision, especially long-sight, the squint can be helped or removed through e.g. LASIK. You said your glasses correct your vision and the squint. If your glasses do NOT contain a prism to correct the misalignment of your eyes, then laser correction will likely do the same job as your glasses. The closest test is how your vision and squint is when fully correcting your focus with contact lenses, but glasses can perform a similar role. If your glasses contain a prism, then you will still need to wear glasses with a prism afterwards.

Amar asked:

You mentioned using mytomycin C for LASEK procedures. Is this generally a safe drug to use on ones corneas? In your opinion, what does a femtosecond laser offer over a microkeratome procedure. Can it be said if one is better than the other? Also, in higher prescriptions, given all other parameters are met including corneal thickness, which flap creation technique would be more advisable. Can both options create buttonholes?
Thank you so much for your help, Amar

Thanks Amar. MMC (mitomycin) appears to be safe. In 2000, Majdamur and colleagues were the first to describe MMC effects on post-PRK and postradial keratotomy subepithelial fibrosis (haze formation). We have not seen significant complications with its use over the past decade and I do use it on eyes where there is greater risk of haze.
I have written plenty on femtosecond lasers and blade keratomes, and you can see those posts under the lasik and safety categories. Both can create buttonholes, but the great advantage of the femotsecond laser is that you can identify the hole without lifting the flap and so get a complication-free healing, which isn’t always the same with a blade cut. In that case, the flap is already lifted by the keratome and there are risks of scarring at the edge of the hole and possible epithelial ingrowth.
Go for the femtosecond flap if you have the option.

Here are the answers to one of today’s questions:

From Ian, who said:

A fantastic site, very informative.  A quick (but naive) question.  I am very excited about the prospect of having intra Lasik to correct a minus 5 prescription.  However, I have read some scare stories on US web sites which suggest that it is possible that the cornea can be irreparably damaged during the flap creation process.  How often have you seen this happen?

Thanks Ian. Correcting a -5.00D prescription is quite routine and should give you no problems. You mentioned IntraLASIK, which is a brand name when the Intralase femtosecond laser is used to create a Lasik flap. I don’t know whether you refer to femtosecond Lasik in general or you are looking at the Intralase machine for treatment. Manufacturers AMO now refer to iLasik rather than IntraLASIK. Other version are Z-LASIK when the Ziemer femtosecond laser is used, and Visumax and Femtec systems from other companies.

The femtosecond lasers have replaced the blade-cut keratome Lasik procedures in many clinics. One of the reasons to do this is to eliminate the possibility of a seriously damaged flap from a keratome, which I have seen happen (although it’s occurrence is rare). I have never seen this occur with a femtosecond laser and it is not possible to ‘mangle’ a flap with these technologies, so added safety.

Here is a recent question I was asked on whether LASIK is suitable for thin corneas:

“Dear David, I wrote a while ago to ask whether Z Lasik gave greater scope to those of us with thin corneas for having Lasik as opposed to Lasek or PRK. At the time, I didn’t know what my actual measurement was – I have since had my notes from my previous check and they read L 465, R 473. However, reading recent posts on your blog I see that you do not recommend any ‘flap cutting’ to anyone with a corneal thickness measurement of under 500. I suppose what I’m asking, is if that is completely set in stone? Does Z Lasik not allow you to consider previously borderline cases?“,

And another question on the same topic:

Hi Dave,
I have myopia of -6.5 and -2 for astigma. I have a corneal thickness of 490 micron. I went for 2 different consultations. One surgeon recommend that i should do PRK because he said that it is safer than iLasik (intralase) due to zero flap create. The other doctor recommended me to go with Intralase because he said that it is possible. I know that both procedures are safe. But i am just a bit concern in the long term. Also, what is the down side of having intralase over PRK or the other way around?

Average central corneal thickness is 530-540 microns. Many surgeons, myself included, don’t cut LASIK flaps in corneas less than 500 microns, although there are surgeons who will. In the first question, this person had very thin corneas (465 and 473 microns) and in my opinion should NOT have LASIK. In the second, the corneas are thin at 490 microns, but not excessively so.

It is true that being able to create very accurate LASIK flaps with the new femtosecond lasers (e.g. Ziemer, Intralase, Zeiss) leaves more tissue behind and so allowing larger treatments. More on this topic in my next post.

The choices can seem bewildering! You want to have laser eye treatment e.g LASIK and now you need to choose the clinic for your surgery.

But which one?

There are over 100 clinics in the UK, although 75% of those are made up of only three large business laser chains: Optical Express, Optimax and Ultralase. The other 25% are mainly owned by doctors and optometrists, who practice from their centres.

80% of UK centres have adopted the advanced blade-free femtosecond lasers, and so now offer blade-free LASIK (a.k.a all-laser LASIK, Intralase, Z-LASIK). These include:  FOCUS Laser Vision , Optimax, Optical Express, Ultralase, Moorfields Eye Hospital and Centre for Sight.

20% of UK centres have not yet invested in this technology, and only offer bladed LASIK, where a device containing a short blade is used to cut the LASIK flap. These centres include Advance VisionCare and Accuvision in London

Having your laser eye treatment with a blade free femtosecond method has rapidly become the standard of care for UK LASIK laser eye surgery.

For LASIK laser eye surgery safety, there are 3 things you must look for when you plan to go ahead. This LASIK safety trio means a more accurate result and the safest procedure we know of today:

1. Choose a blade-free all laser LASIK technique – using the latest femtosecond lasers means no blade is used in the surgery. Check with any clinic you talk to that they can offer blade-free LASIK – if they can’t then they are out of date and should be avoided.
2. Wavefront-based LASIK is a must today, so make sure you go for that option. For example, at FOCUS Laser Vision we only do wavefront treatments so that is taken care of. At other centres such as Optical Express, do not choose their non-wavefront option.
3. Get the safety and reassurance of NHS consultant corneal specialist surgeons to do your treatment – the three laser eye chains do not offer this for the great majority of their treatments. Premier centres like Moorfields Eye Hospital, Centre for Sight and FOCUS Laser Vision do.

This is a common question about laser eye surgery safety I get asked by patients:

What happens if my vision isn’t right after treatment?

Most people don’t realise that the effect of laser eye surgery, including LASIK, LASEK and PRK procedures, CAN be fully reversed.

Although this isn’t necessary because if the prescription for glasses hasn’t been fully corrected then a second treatment is easily performed to fix that and stay free from the need for glasses or contact lenses. If the effect of the laser correction is a bit too strong or too weak, we call this an over-correction or an under-correction respectively.

All over- and under-corrections can be treated easily. In fact, as I mentioned, the whole laser eye treatment can be reversed. The move over to the Ziemer blade free system (Z-LASIK) has dramatically reduced the need to re-do LASIK treatments.

Most clinics quote enhancement rates of around 5%.  BUT with Z-LASIK for short-sight I have only had to adjust one case in the last 200, so that’s a 0.5% rate. Without any hype or spin, that’s just very impressive and a great step forward.

To fully reverse the effect of e.g. a short-sighted laser eye treatment, we remove some tissue from the outer part of the cornea to put the corneal curvature back to where it started. So now an equal amount of tissue has been removed across the cornea and so the focus would be back where it started. Of course, the cornea is a little thinner than before, but still strong enough for its role.

It’s the accuracy of the dual laser approach that allows such a very low enhancement rate, which means 99.5% of short-sighted patients are on target and very happy with only one treatment and without the need for a top-up.

IMPORTANT NEWS for those people considering having LASIK laser eye surgery.

There appears to be a fundamental difference between LASIK flaps cut either with a blade or created with a laser. Laser created flaps mean a safer surgery as the results are more accurate, so fewer enhancements needed, and the eye is left stronger.

Making a replaceable flap is the first part of the LASIK procedure, just prior to reshaping the cornea to correct vision. Until recently (and still in many clinics) the flap was made by a physical cut with a very sharp razor blade contained within a precision device. However several clinics and the major three chain operators have invested in femtosecond lasers to create the corneal flap without the need for a blade.

This is known as blade-free LASIK, dual laser LASIK, Z-LASIK or IntraLASIK depending on which clinic you are talking to.

We know that thicker flaps cut with a blade do not fully heal and can be lifted up surgically even many years later. Traditional blade flaps are thicker and cut deeper into the cornea. However laser flaps are thinner and leave the eye stronger afterwards.

However a key difference highlighted by Professor John Marshall in London is that because these very thin laser flaps pass through near the surface of the cornea where the collagen is different from deeper down, they actually heal down and are not able to be lifted later on. This means the eye regains strength again with a laser flap, but not with a blade flap.

Newer blade machines have been introduced in 2008 and 2009 that cut thinner flaps to compete with the thin femtosecond laser flaps which should benefit from the better healing seen in sub-120 micron flaps

My recommendation to you when choosing a clinic is to be able to select to have a femtosecond laser procedure at a clinic that has that technology. They are more expensive than blade procedures (expect to pay around £300 more per eye) but well worth the likelihood of a long-term increase in safety.

You might want to take a look at the laser eye surgery Lifetime Care Guarantee introduced at FOCUS Laser Vision (www.focusclinics.com/treatments_after.php). There are millions of people who would like to have laser eye surgery, although worries about possible complications is the quoted main reason that people have not yet gone ahead.

People have been looking for peace of mind and want to know that a clinic will take care of them afterwards.

Currently only FOCUS Laser Vision and Ultralase offer a lifetime care guarantee after laser eye surgery.

The biggest thought in every patient’s mind is about safety and that is exactly how it should be. As a prospective laser eye surgery patient (LASIK or PRK) you need to do a little research beforehand, so take a look at various clinics’ websites. Check the FOCUS Laser Vision or Ultralase websites for more details of their Lifetime Care Guarantees.

You can also check out Optimax, Optical Express or Moorfields (or any other UK clinics in fact) but none of these clinics offer a lifetime guarantee.

Continuing from yesterday:
Some surgeons recommend PRK or LASEK (both forms of surface laser eye treatment and basically the same) over LASIK. The article referred to by Kay in her original post and advocating LASEK was written by ophthalmic surgeon Sunil Shah, who was one of the creators of that particular approach (and so has some personal interest in writing about it one presumes).

One of the very vocal and respected advocates of surface laser (PRK) over keratome LASIK was Professor John Marshall in London, UK, a founding father of laser eye surgery back in the 80s. Prof Marshall argued convincingly that the cornea was considerable stronger after PRK compared to mechanical (thicker flap) keratome LASIK.

However, the game has changed with the introduction of femtosecond lasers with much thinner flaps. Even Professor Marshall now supports the move to thin-flap LASIK using a dual laser, blade-free approach.

So if a clinic cannot offer dual laser LASIK (and many still can’t) they may offer PRK/LASEK instead. There are some clinical reasons to perform PRK instead of LASIK but the percentage of these cases has shrunk from 10-15% down to around 5% today, with dual laser technology. Patients much prefer femto-laser LASIK over PRK, as the latter is fairly unpleasant for a few days post-op.

In summary, there are definite clinical reasons why we as treating clinics have moved over to wavefront LASIK and using a blade-free dual laser approach. More accurate treatments so better vision, removal of an older mechanical device technology and improved long-term safety.