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.

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.

WHENEVER a patient undergoes any type of surgical treatment there is a possibility for a complication. The main questions are: are these complications serious and could affect the final outcome – or minor and short lived and which do not affect the ultimate vision? Also, what are the chances of a complication occurring that would require adjustment or follow-up correction?

LASIK surgery is no different from any other operation, despite how it may be pitched by some clinics, in that it IS a surgical correction and should be approached as such. However, and fortunately, most complications are in fact minor and easily resolved.

Technology

LASIK risk continues to drop as doctors and engineers perfect the equipment used in the treatment. Advances in technology have made a big part of the difference here so make sure you are getting that latest equipment and not an older fashioned approach.

The risks drop as doctors continue to screen for the right candidates to have the procedure, and screen out those with any chance to have a problem. Research also shows that with the right pre-testing and surgical handling, the risk of complications in LASIK surgery is less than 1% and most of these are minor problems which will be fully corrected afterwards without undue ongoing problems.

The most common risk with LASIK surgery is a complication with the flap, created by the surgeon in the first part of the procedure.

In the original LASIK procedure, the flap is cut by a surgical blade device known as a microkeratome. The blade cut is, however, less precise than those from newer femtosecond lasers.

Blade Free LASIK

LASIK risk is reduced by the newer “bladeless” dual laser technique.

In bladeless (blade free) LASIK surgery, the risk of complications is lower because the blade or microkeratome is no longer used. It is replaced by special type of infra-red laser that greatly reduces human or machine error.

The original laser to make a LASIK flap came from the USA, manufactured by Intralase. You may see this surgery called IntraLASIK or iLASIK.

The newer machine is from Switzerland and produced by the Ziemer Group of companies. There appear to be some advantages of the tighter focus of the Swiss laser. This procedure may be called Z-LASIK.

Summary

When assessing these LASIK risks it is recommended that when you are considering surgery that you ask your doctor what technology the clinic has and whether or not a blade free dual laser approach will be used.

Let’s look at the second of Carlo’s questions on laser eye surgery:

My name is Carlo and I have recently discovered this great blog. I would like to ask a couple of questions regarding eye surgery:
Question: Is it true that the LASIK procedure has not been approved for air-force pilots and astronauts in the US but PRK and LASEK has?

No, this is not true.

LASIK was approved for use on consumers a decade ago and reportedly more than 11 million LASIK procedures have been performed in the US. This means LASIK laser eye surgery is the most-common American elective surgical procedure.

NASA has approved LASIK for use on pilots, mission and payload specialists who face extreme and often physically demanding conditions in space. The all-laser LASIK technologies, using a blade free femtosecond laser approach, have also been cleared for U.S. military personnel, including most recently Air Force pilots.

“NASA’s approval is further evidence that today’s LASIK exceeds all established standards of safety and effectiveness,” said Steven Schallhorn, M.D., retired captain of the U.S. Navy.

Though LASIK has been around for a long time, concerns about the harsh environment in aviation prevented its use. To date, aero-medical professionals have been cautious of employing the procedure on military pilots who often encounter environmental extremes such as high altitude, dry air, wind exposure and “G” forces. In space, other conditions further add even higher levels of concern due to the very high level of precision needed during flight and space walks.

Defense Department’s research into laser vision correction included the following results:

# In a study of different methods to create the LASIK flap, 370 naval personnel underwent bilateral (both eyes) wavefront-guided LASIK with either the femtosecond laser (blade free) or microkeratome blade. One week after surgery more than 76 percent of femtosecond laser patients achieved an uncorrected visual acuity of at least 20/16 (better than 20/20) compared to only 58 percent of microkeratome patients

# In an evaluation of 785 pilots, 89% of Navy aviators evaluated their ability to land on an aircraft carrier as moderately to significantly better after laser eye surgery. None said it was worse after treatment

# A separate study determined that over 90 percent of marksmen had improvement in marksmanship skills after laser eye surgery; an impressive finding given the visual precision of marksmen

LASIK, particularly blade free femtosecond LASIK, appears to have established itself as a very effective and reliable procedure. The move from blade to laser blade free has allowed another significant improvement in results (now targeting better than 20/20 as a standard of care) according to the above research findings.

I recently received this email with a couple of great questions:

My name is Carlo and I have recently discovered this great blog. I would like to ask a couple of questions regarding eye surgery:

a) Can the creation of a flap in the eye potentially lead to problems? Should PRK and LASEK be better in the long run for patients?
b) Is it true that the LASIK procedure has not been approved for air-force pilots and astronauts in the US but PRK and LASEK has?

There is a lot of confusion on the web about those issues. Could you spend some time clarifying that?

Let’s look at the first question now and I will address the second in a subsequent posting.
The majority of surgeons use the LASIK technique, where a thin flap is created in the top part of the cornea before applying the vision correction laser. More than 90% of laser eye surgery procedures are LASIK rather than surface laser treatments (PRK or LASEK).

There has not been any research to show signifiant differences in results between LASIK and PRK for short sight so whichever you choose to have, the final outcome will be the same. However, for long sight or reading vision correction, LASIK appears to give a more stable results and this is my preferred method for these types of prescription.

But let’s stay with short sight for the moment, where the vision and stability are not affected by the choice of procedure. It then comes down to safety. I personally used to prefer PRK over LASIK due to the small but measurable complications arising from using a blade to cut a flap. At that time, when I asked myself which procedure I would have, it would have been PRK.

However, with the arrival of the very safe and predictable laser flap makers (femtosecond lasers) I no longer subscribe to that view and would personally now choose to have all-laser LASIK. The femtosecond lasers create a very predictable and thin flap time after time, with greater precision and safety than the mechanical keratomes could. Early research also shows improved vision results, especially in reaching the very high target of better than 20/20 vision.

You still need an expert surgeon and a very thorough examination and consultation because there are points we can detect which do predict a bigger chance of having a problem in the long term. Such patients need to be screened out of the LASIK or PRK process and should not have surgery.

So choose an expert centre with an expert surgeon and you will have a safe and predictable experience and result. You can comfortably opt for LASIK over PRK/LASEK without worries for the long term.

Certainly, patients much prefer LASIK as vision is very good within a few hours (even quicker with our Z-LASIK approach) and they can be back at work the next day, rather than needing to take several days off work. Also, most patients find PRK or LASEK to be a pretty painful experience for 2-3 days after correction (the procedure itself is painless).

I get asked about the so-called ‘femtosecond‘ lasers now being used in LASIK laser eye surgery, and what these devices do. OK, here are the answers.

First of all, LASIK eye surgery is a laser procedure with two parts. First we have to make a thin flap from the top part of the cornea, basically a thin hinged layer we can temporarily fold to the side (painlessly!).

Next we use an ‘excimer‘ laser to reshape the exposed cornea to correct the vision focusing problem. The laser will polish away certain areas, depending on your prescription, to bring back clear vision.

The flap is put back in place and heals over very quickly. The eye feels gritty or scratchy for about 3-4 hours only. OK, so far so good.

For the first stage, making a flap, we have used a mechanical device called a keratome (or microkeratome). Keratomes have been around for 50 years and use a blade to make a controlled cut. This stage is where significant complications can occur, so we have been looking for a way to make this corneal flap but without the need for a blade.

Along come femtosecond lasers.

The eye lasers use ultra-short infra-red low energy pulses to create microscopic bubbles at a precise depth below the surface of the cornea. If you do this millions of times, you can create a super precise separation as a sheet, and hence a near-perfect corneal flap, which you can now fold to the side ready for vision correction with a second laser.

The femtosecond laser means we no longer run risks from using a blade to cut a flap. This means safer LASIK eye surgery.

You can watch a video of femtosecond laser eye surgery here.

More on femtosecond lasers coming soon.

Definition for femtosecond:

(This definition follows U.S. usage in which a billion is a thousand million and a trillion is a 1 followed by 12 zeros.)

A femtosecond is one millionth of a nanosecond or 10^-15 of a second and is a measurement sometimes used in laser technology. So that’s one billionth of a millionth of a second! As a comparison, one femtosecond to a second is like one second to 32 million years.

For comparison, a millisecond (ms or msec) is one thousandth of a second and is commonly used in measuring the time to read to or write from a CD-ROM player.

A microsecond (µs) is one millionth (10^-6) of a second.

A nanosecond (ns or nsec) is one billionth (10^-9) of a second and is a common measurement of read or write access time to random access memory. A picosecond is one trillionth (10^-12) of a second, or one millionth of a microsecond. An attosecond is one quintillionth (10^-18) of a second and is a term used in photon research.

[tags] LASIK, femtosecond, laser eye surgery, safety, risks, compications [/tags]

 We have been using the Ziemer LDV for 3 weeks now with great results. Vision results and flap creation have been excellent and without any complications.

For eyes with pre-existing corneal scars there has always been a question mark over the ability of femtosecond lasers to create LASIK flaps as the scar tissue may prevent the laser from passing through the tissue. Intralase users report that they found an inability perform LASIK to treat eyes that have pre-existing moderate to dense corneal scars.

Unlike the Intralase (American made femtosecond eye laser), the Swiss-made LDV will pass through even fairly dense corneal scars without a problem. So far the LDV has created excellent flaps in these cases. I will keep you updated on our progress.

[tags] laser eye surgery, complications, femtosecond, flap, Intralase, LASIK, risks, safety, Z-LASIK, Ziemer [/tags]