Lasik Eyes Surgery - What We Should Really Tell LASIK patients

Author

What We Should Really Tell LASIK patients

LASIKtruth

2005-04-19, 10:51 am

This is an article by Dr. Jack Holliday explaining that all LASIK patients
lose contrast sensititivy and why this happens. NO prospective patient
wants to lose contrast sensitivity. This is why pre and post-op contrast
sensitivity should be measured and the RESULTS reported to patients.

This little tidbit of LASIK TRUTH, if widely known would be the death of
LASIK in and of itself. As if the nerve damage and ocular surface damage
were not enough disincentive already.

http://www.revophth.com/1999/May_ar...RPE9f5lasik.htm

Excerpts:

Because excimer laser manufacturers were unaware of the true physiologic
shape of the human cornea, both procedures reduce contrast sensitivity in
low-light conditions.

Excimers assume all corneas look like this, a sphere. Unfortunately, that's
not the case. Function follows form.

To understand the problem, it's important to understand the impact of the
cornea's shape on the light that passes through it.

The natural shape of most corneas is what's called prolate. A prolate
surface is shaped something like the head of a bullet. It is steep curvature
in the center, but flatter toward the periphery (see figure 1). As the

cornea flattens, its dioptric power decreases. The net effect is that
central and peripheral light rays all focus at a single point inside the
eye, regardless of pupil size.

In a small percentage of the population, the cornea is spherical. In these
patients, the focus of rays shifts depending on pupil size. In the daytime,
when the pupil is 3 mm or smaller, most of the rays focus at

one point. At night, when the pupil is dilated, the peripheral rays focus at
a point anterior to that of the central cornea (see figure 2). This results
in night myopia; the optical property is called spherical aberration.

The problem with all excimer lasers on the market today is twofold. First,
the engineers assumed that the cornea is spherical rather than prolate.
Second, they assumed that their job was to reshape a relatively

steep sphere into a relatively flat sphere, rather than to reshape a steep
prolate into a flatter prolate.

As a result, excimer lasers actually reshape prolate corneas into what is
known as an oblate. An oblate is shaped like the cross-section of a
hamburger bun, flatter in the center but steeper in the periphery (see

figure 3). This shape is actually optically worse than a sphere, because now
the peripheral rays are bent even more powerfully than in the periphery of a
sphere, causing even more pronounced spherical aberration when the pupil
dilates. Unlike the haloes that result from a too-small optical zone, this
problem affects every patient who undergoes an excimer laser procedure to
some extent. Like the halo problem, the oblate dilemma is worst for patients
whose pupils dilate widely at night.

....Also, at the six-month mark, the average contrast threshold in dark
conditions was 2.3 lines poorer than at

baseline, though it returned to baseline under medium and high brightness
levels.

It's important to remember that these patients' pupils did not dilate
outside the ablation zone. Patients with pupils that do dilate this much
could be expected to have even lower contrast sensitivity.

(HEY GLENN, AT 6 MONTHS LASIK PATIENTS CAN'T SEE WELLIN THE DARK! SO MUCH
FOR YOUR 'EVERYTHING IS GREAT AT 6 MONTHS HAGELE_HOGWASH!)

The first step is to make sure you take an accurate measurement of pupil
size. As I mentioned, the larger the pupil, the more optical aberration
patients will experience from the oblate cornea effect. Large-

pupil patients are also much more likely to see haloes at night, because
their pupil exceeds the ablation zone.

To measure the pupil, I simply darken the room and then aim a penlight
covered by a cobalt blue filter from the temporal side of the eye towards
the nose. Blue light is also very inefficient at causing

pupillary reflex. I then measure the pupil with a pupil gauge manufactured
by Asico. I have recently begun to use the Colvard infrared Pupillometer. If
the patient appears to dilate widely under dim lighting, I

use this pupillometer, which is much more accurate and requires no visible
light.

Remember that high correction and astigmatic correction both can effectively
reduce the size of the optical zone. This will intensify

the halo effect.

serebel

2005-04-19, 10:51 am

All this and millions of people are walking out after their surgeries
able to see just fine. Oh yeah, this 'll kill RS alright.

SErebel

Glenn - USAEyes.org

2005-04-19, 10:51 am

Yes, six years ago, first generation lasers, less understanding than
today, no wavefront analysis or guided ablation profiles.

Things change.

Glenn Hagele
Executive Director
Council for Refractive Surgery Quality Assurance

Email to glenn dot hagele at usaeyes dot org

http://www.USAEyes.org
http://www.ComplicatedEyes.org

I am not a doctor.

Pauli Soininen

2005-04-19, 10:51 am

Well, my eyes are lasered to Prolate (Zeiss MEL-80) and basically the newest
wavefront analysis was used (and a doctor with 14 year experience on
refractive surgery) but I still have those exact spreading problems. (My
guess is that they won't go away since this is the 3rd month and there has
been no change or improvement whatsoever after two days of surgery.)

Notice that I'm only making an observation and not trying to judge anything.

LASIKtruth

2005-04-19, 10:59 pm

Wavefront doesn't do anything but reduce those horrible induced aberrations
by 20%. In the process it eats much more precious corneal tissue than
standard LASIK. Hello ectasia.

Many surgeons use so much tissue in a first round wavefront treatment, they
give the patients a 'one shot deal' and they don't tell them they won't have
enough tissue in reserve for an enhancement. Now that's criminal behavior.

Instead of at least a doubling of your induced corneal distortions with
standard LASIK you get... well 20% less than a doubling with a wavefront
treatment. You still wind up with corneal nerve damaged and a flattened
lumpy cornea that doesn't spread tear film as well as your pre-op round,
healthy cornea.

There are some problems with LASIK that have been hyped but not fixed (eg.
wavefront is a SHAM) and others that are just plain not fixable, such as the
creation of the LASIK flap. Dangerous to create, weakens the cornea,
vulnerable to later infection and injury.

Folks, think twice about refractive surgery. Glenn is pimping LASIK for cash
so he's not the best source of information. Nor are his websites. Check out
the new FBA LASIK websites. They have updated them and the LASIK warnings
are much more DIRE. Particularly in regard to pupil size. You owe yourself a
visit there if you are contemplating refractive surgery, and also a visit to
the archives of VSRN, the former Surgical Eyes. Read there for a good long
time, read patient stories and think about what your life may be like should
you be one of the unlucky victims of a poor refractive surgery outcome.

Some things never change. New casualties are popping up every day. If you
hear that these things don't happen with today's new lasers... don't listen.
It's just more Hagele-hogwash.

"Glenn - USAEyes.org" <glenn.hageleSTOPSPAM@USAEyes.org> wrote in message
news:j6t861d0ausdbrlh05didop5l17mvqjgl8@4ax.com...
> Yes, six years ago, first generation lasers, less understanding than
> today, no wavefront analysis or guided ablation profiles.
>
> Things change.
>
> Glenn Hagele
> Executive Director
> Council for Refractive Surgery Quality Assurance
>
> Email to glenn dot hagele at usaeyes dot org
>
> http://www.USAEyes.org
> http://www.ComplicatedEyes.org
>
> I am not a doctor.

serebel

2005-04-19, 11:00 pm

Definately read SE, what you'll find are a handful of lunatics who have
posted for years. That would be why you'll see tons of posts.

SErebel

Glenn - USAEyes.org

2005-04-20, 8:54 am

ANY reduction in the introduction of additional higher order
aberrations (HOA) is desirable, however the information stated by
LASIKTruth is inaccurate. All currently US approved wavefront-guided
excimer lasers providing "custom" LASIK and PRK are providing
significant better results than just a 20% decrease in induction of
HOA. You need to review the more current data.

The amount of tissue that will be removed is generally greater with
wavefront-guided surgery when compared to conventional, but the
patient's corneal thickness can be measured preoperatively, the
thickness of the flap can be predicted within a reasonable margin of
error (Intralase has a big advantage on this point), and the amount of
untouched cornea that will remain after surgery can be evaluated to
determine if the patient would have the postoperative stability
needed.

Conventional LASIK rarely doubles HOA, however if preoperative HOA are
abnormally low, a doubling may occur. In many cases, doubling the HOA
may only put the patient up to the level of HOA of the average
patient. Some individual HOA as represented in Zernike polynomials
may double, but the importance of that particular HOA varies case by
case.

What I have seen at the ASCRS convention is study after study that
shows not only does wavefront provide a better outcome than
conventional for the majority of patients within the treatable range,
but it is now reducing HOA more than ever before. This can be
attributed to refinement in the lasers, but also in refinement of the
preoperative evaluations and surgical techniques that reduce the risk
of problematic outcomes.

When looking at a topography, Orbscan, or wavefront analysis of a
cornea after LASIK, it does appear more "bumpy" than before surgery,
but the real question is the relevance of those "bumps". In a
peer-reviewed study from Alexandria Egypt, 100% of 50 eyes that had
wavefront-guided PRK and 100% of eyes that had wavefront-guided LASIK
achieved 20/16 or better visual acuity. There were no reports of
objective or subjective complications. The myopic corrective range
was wide, including higher myopes, with a mean of about 3.50 diopters.
The actual purpose of the study was to determine if wavefront-guided
PRK provided a clinically significant better result than
wavefront-guided LASIK. The study shows that the reduction of HOA
overall was greater with PRK than LASIK, the induction of HOA overall
was less with PRK than LASIK, and the outcome of the first three
orders of Zernike HOA (most important) were better with PRK, but who
cares? When all the patients received 20/16 uncomplicated uncorrected
vision or better, does the presences of "bumps" in a topography or
wavefront scan really matter? This is like making fun of a Panda
because he does not do well at geometry.

I hasten to warn that these outcomes are NOT the norm that one would
expect. In fact, physicians in the audience were surprised at the
results, and a flurry of questions trying to find some reason for
these unusually excellent outcomes ensued.

About the only thing in LASIKTruth's post with which I can agree is to
think twice abut LASIK or any refractive surgery. If anything, these
kind of result reports make LASIK MORE dangerous, because I fear
people will take good results for granted and not do the research and
due diligence needed to make an informed decision.

As for the accusation that I sell LASIK, I do not. Any reasonable
person can see this from my posts and from the content of our
websites. I have never privately or publicly told anyone they should
have refractive surgery of any kind. My income isn't any different if
someone has refractive surgery or not, or has refractive surgery with
a CRSQA Certified Refractive Surgeon or not. I will provide
researched information and highly recommend anyone serious about
surgery consider using a CRSQA certified surgeon, but the decision to
undergo elective surgery is the patient's and the patient's alone.

For some people, if you are not adamantly against LASIK in all
circumstances, then you are a "LASIK pimp"

Glenn Hagele
Executive Director
Council for Refractive Surgery Quality Assurance

Email to glenn dot hagele at usaeyes dot org

http://www.USAEyes.org
http://www.ComplicatedEyes.org

I am not a doctor.