Dr. Steven Schallhorn's study is a complete sham. When questioned during deposition about his one and only 8 mm pupil patient in his study, he said he did not know if that patient dropped out of the study. And he only had one patient with a 7.5 mm pupil. The 7.5 mm patient was experiencing visual disturbances at night.

His study mixed patients with astigmatic corrections with patients having pure spherical corrections. That's like comparing apples to oranges. The sizes of the OZs were different.

There is a 10-year old PRK study that Dr. Steven Schallhorn conducted. The ablation zone was 6 mm. The conclusion states that one patient experienced a prolonged reduction in the quality of vision at night. You have to get the full-text to find out that the size of that patient's pupils (AT 10 LUX) was 7 mm. The 7 mm pupil patient refused treatment in the 2nd eye.

There could be an "army" of night-vision impaired patients out there who were treated by Dr. Steven Schallhorn and his colleagues. And they are being lied to -- told that large pupil patients are no more at risk for NVD than small pupil patients. They are being told that all patients, regardless of pupil size, have the same risk for loss of visual quality after LASIK. Absolute lies.

Patients deserve to be told the truth. They are not stupid. They can understand loss of contrast sensitivity if you take the time to explain it to them or show them pictures. Dr. Steven Schallhorn does not believe patients should be informed of loss of contrast sensitivity -- he said so during a deposition against a patient with large pupils. He also said he does not measure pupils pre-operatively because, as a military doctor, he cannot be sued for malpractice.

Dr. Steven Schallhorn should leave the research to competent doctors -- doctors who are interested in the truth and the well-being of patients, not in covering up for the RS industry.

His fly-by-the-seat-of-his-pants mentality belongs back in the c o c k -pit, not in a medical setting performing elective eye surgery.

More on this study later. Stay tuned.

To which study do you refer?

Pupil size and quality of vision after LASIK.

Ophthalmology. 2003 Aug;110 8:1606-14.

Schallhorn SC, Kaupp SE, Tanzer DJ, Tidwell J, Laurent J, Bourque LB.

I am seeking to publish a booklet that attorneys can use to debunk this so-called "expert". If you would like to author a booklet, please send it to me.

One very interesting aspect of the Schallhorn study is the lack of any objective testing post-operatively. Wavefront aberrometry and contrast sensitivity testing were available -- why didn't he use them? He relied on a poorly designed questionnaire. (You can design a study to draw any conclusion you desire.)

A little more detail on the astigmatism factor -- 90 eyes (100 patients were enrolled) received an elliptical ablation with the minor axis optical zone ranging from 4.5 to 5.8 mm. 110 eyes received a 6 mm spherical ablation. As I said before, Dr. Steven Schallhorn mixed apples with oranges.

He classified the pupil sizes as follows:

Pupils of 5.0 mm or less - Small
Pupils 5.5 and 6.0 mm - Medium
Pupils 6.5 and greater - Large

Keep in mind that the optical zone used in this study was 6 mm.

OK, time for a quick lesson in "effective optical zones".

The part of the cornea that the laser attempts to ablate the full refractive correction is called the "optical zone".

The part of the cornea that is tapered or blended is call the transition zone or blend zone. It does not receive the full refractive correction. The purpse of the blend/transition zone is to prevent a sharp knee between the treated area and untreated area of the cornea. The laser used by Dr. Schallhorn in this study did not use a blend zone. It used a 6 mm optical zone, no blend. These patients would have an abrupt transition between the treated and untreated cornea.

The entire area treated by the laser, including the optical zone and the blend zone is called the treatment zone or ablation zone. You might hear a LASIK counselor say, "We can treat patients with large pupils because our laser has an 8 mm ablation zone!" The LASIK counselor is an idiot and might not even be aware that only 6 or 6.5 mm is actually receiving the full correction. (I spoke to a LASIK counselor on the phone one day who insisted that their laser could do a 10 mm LASIK treatment. When I asked what the actual optical zone was, he continued to insist it was 10 mm. I told him to put me on hold and go ask the surgeon. After a few minutes he returned to the line to tell me that the optical zone was 6.5 mm.)

OK, now here's the tricky part -- the "effective optical zone", a/k/a the "functional optical zone".

No one can explain it better than Dr. Jack Holladay:

Early excimer systems, for several reasons, tended to remove less tissue than intended peripherally, resulting in greater positive spherical aberration in the cornea. Those early systems ablated less efficiently in the periphery of the cornea because they were not calibrated on spheres, Dr. Holladay said.

“They were calibrated on flat surfaces, but the cornea is a dome. The only time the laser hits the cornea perpendicularly is at vertex normal — the apex of the cornea — and from then on out the effectiveness of the laser diminishes because it’s hitting the surface obliquely,” he said.

The oblique incidence of the laser on the periphery of the cornea causes a decrease in the efficacy of ablation for several reasons, he said. First, the corneal surface reflects more and transmits less light when the light strikes it obliquely. Second, whether delivered in a broad beam or a flying spot, the energy is spread out over a larger area (an oval rather than a circle), so the effective fluence delivered to the cornea is diminished. Third, the reduction in tissue removal is greater than the reduction in fluence.

“When you cut the fluence by 25%, you remove a lot less tissue,” he said. “You may remove only 50% of what you intended. So the result is, the reduction in tissue removal is greater than would have been predicted by just the difference in reflectance, transmittance and delivered fluence to the cornea. It’s all part of what I call the radial compensation function.”

Because manufacturers did not anticipate the effect of this radial compensation function, the effective optical zone of early excimer systems tended to decrease with greater amounts of refractive correction, he said. The greater the treatment, the greater the discrepancy between the intended amount of correction in the periphery and the actual correction achieved.

Note that Dr. Holladay stated that the greater the treatment, the greater the discrepancy between the optical zone treated by the laser and the "effective" optical zone-- the area that was actually fully corrected.

A patient with low myopia will have a larger effective optical zone than a patient with high myopia.

Now, back to Schallhorn. Not only did he mix patients with and without astigmatism (varying the size of the optical zone on the minor axis), he also mixed patients with varying degrees of myopia. The range of myopia in this study was -2.88 to -9.25D. The low myopes would end up with larger EOZs (effective optical zones) than the high myopes. This is not a valid study.

Let's say you have a -3D patient with no astigmastism, and this patient has 6.5 mm pupils (classified as large in Schallhorn's study). After LASIK with a 6 mm OZ, this patient probably has an EOZ of at least 5.5 or more. This patient will probably experience minor NVD.

Another patient is -9D with astigmatism, and this guy has 6 mm pupils (classified as medium in Schallhorn's study). The programmed optical zone is 6 x 5.0 mm (to correct astigmatism). Due to the high myopia, this patient is going to have a small EOZ, maybe around 5 x 4.0 mm, probably even less. This patient most likely will experience significant NVD.

The first patient with large pupils has only minor problems. The second patient had medium pupils, and is quite unhappy. Bingo! Pupil size has no correlation, right? At least that's how Schallhorn sees it.

Now can you begin to see the flaws in this study?

And we're not done.

Stay tuned.

Next lesson in tearing apart Schallhorn -- methodology of obtaining pupil size measurements.

Schallhorn's study states, " The pupil diameter was measured under low light conditions (<5 lux) using the Colvard Pupillometer..."

Right there we have a huge problem with Schallhorn. 5 lux is NOT scotopic. Why is this important? Because we don't really know the scotopic pupil sizes of these patients; therefore his conclusions are NOT VALID!

Take a look at this:

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http://www.ncbi.nlm.nih.gov/entrez/quer ... query_hl=1


J Refract Surg. 2004 Jul-Aug;20(4):337-42. Related Articles, Links


Comment in:
J Refract Surg. 2005 May-Jun;21(3):303.

Pupil size in refractive surgery candidates.

Netto MV, Ambrosio R Jr, Wilson SE.

Department of Ophthalmology, University of Washington, Seattle, WA, USA.

PURPOSE: To assess pupil size measurements obtained under scotopic and mesopic conditions with the Procyon pupillometer and under photopic conditions with the Humphrey videokeratographer.

METHODS: The pupil sizes of 96 candidates for refractive surgery (192 eyes) were measured with the Procyon pupillometer PS2000 SA and the Humphrey Atlas 992 corneal topographer. Anisocoria and pupillary unrest were analyzed according to gender (two groups: 51 females and 45 males), age (five groups: 20 to 30 yr, 31 to 40 yr, 41 to 50 yr, 51 to 60 yr, older than 60 yr) and level of refraction (five groups: >-6.00 D SE, -6.00 to -3.00 D SE, -3.00 to 0 D SE, 0 to +2.50 D SE, +2.50 to +5.00 D SE).

RESULTS: The median value of pupil diameter measured with the Procyon pupillometer at the scotopic (0.04 lux), mesopic-low (0.4 lux), and mesopic-high (4 lux) levels of illumination were 6.54+/-0.88 mm; 5.62+/-0.95 mm, and 4.09+/-0.76 mm, respectively. The median pupil size with the Humphrey topographer was 3.65+/-0.62 mm. Pupillary unrest was highest at the mesopic-high level of illumination, with a median value of 0.31+/-0.34 mm. Median pupil size measured with both instruments at all light levels dropped significantly after the fifth decade of life (P<.05, ANOVA).

CONCLUSIONS: The Procyon pupillometer and Humphrey videokeratographer revealed an inverse correlation between the pupil size and the age, but no relationship with gender or level of refraction. The Procyon pupillometer provides an objective method for measuring pupil size at controlled light levels with a permanent printed record.

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Note there was a 2 1/2 mm difference between the average scotopic (.04 lux) pupil diameters and the high mesopic (4 lux) pupil diameters.

It's very easy to see how a medium or even small pupil patient with high myopia and astigmatism might report NVD if his/her pupils are really 2.5 mm larger than reported by Schallhorn.

In Schallhorn's study, a patient with 5 mm pupils (classified in the study as small) at high mesopic could actually have 7.5 mm pupils scotopically.

This study is like wet toilet tissue, it falls apart quite easily. And it's about as useful as wet toilet tissue.

Stay tuned for more on defeating Schallhorn's lies.

Instead of just reading the conclusion in the abstract, I wonder how many surgeons who have jumped on the Schallhorn bandwagon have taken the time to read the full-text.

Schallhorn's questionnaire had patients rate the frequency of symptoms, not the severity of symptoms.

If a small or medium pupil patient reported that he/she saw halos around lights at night "Most of the time", and a large pupil patient answered the same way, Schallhorn says there is no correlation to pupil size.

But suppose the small or medium pupil patient's size of the halo is small while the patient with large pupils has massive halos and starbursts?

In this study, patients who report halos at night "most of the time" regardless of the size, are all rated the same -- therefore there is no correlation between pupil size and NVD.


Did we talk about drop-out rate yet? Only 66 subjects (of 100) completed the 6 month (final) questionnaire. Why did 1/3 drop out? Were they happy or unhappy?

When you consider the results of a clinical study, you must consider the Hawthorne effect and cognitive dissonance.

Schallhorn himself speculated that patients might just get used to their new impaired vision after the 2nd eye is treated (in this study they treated one eye at a time, one month apart). There were more complaints during the first month while patients had one good eye for comparison.

More later.

Dr. Jack Holladay talks about the astigmatism factor. Remember, Schallhorn mixed these patients in with other patients with pure spherical corrections which completed invalidated his study.

http://www.osnsupersite.com/default.asp?ID=11816


Before this change, if a plano patient with –4 D of astigmatism was treated with a 6-mm optical zone, the dimensions of the actual treatment on the cornea would have been 4.5 mm by 6 mm.

“This would induce haloes and glare in the shorter axis in a patient with a 6-mm pupil,” Dr. Holladay said. “And because the treatment is not symmetrical, it’s even more bothersome than if it was just circular.”

you can't even get the data for the study. if you ask schallhorn for the data he gives u a list of reasons why the data cant be released.

Wouldn't you like to know what he's trying to hide. He said under oath that he did not recall if his one and only 8 mm pupil patient dropped out of the study. If you're doing a study with the aim of determining whether or not pupil size is important, don't you think you'd be interested in what happened to your only patient with enormous pupils??????

Pupil size and quality of vision after LASIK.

Ophthalmology. 2003 Aug;110 8:1606-14.
Schallhorn SC, Kaupp SE, Tanzer DJ, Tidwell J, Laurent J, Bourque LB


33% of patients dropped out of the Schallhorn study prior to 1 year.

At 1 month and 3 months, there was a statistically significant difference in symptoms between small and large pupil patients.

Patients refractive error was not correlated with their night vision complaints. Patients with residual myopia and astigmatism, regardless of their pupil size, will have night vision complaints. This is different from patients with large pupils and no refractive error that have night vision complaints. By lumping patients with residual refractive error with patients who did not have residual refractive error, Schallhorn could mask the contribution of larger pupil sizes to night vision complaints.

what's interesting to me is that the methodology of the study is so bad it can't justify the conclusion expressed in the title. but, the study was published anyway. why would a journal editor allow such a thing? in my mind, the answer is simply that the industry needed to advance research saying that pupil size was irrelevant to head off other lawsuits. this research was published not because of its scientific merit, but because of legal need.

It would be extremely easy to find out who the editor of Ophthalmology was in 2003.

There is no question that this editor allowed an UNACCCEPTABLE publication to be accepted in this journal - perhaps we should put a little bit of polish on our rebuttal and write it up as a formal request for retraction?

http://groups.google.com/group/alt.lasik-eyes/browse_thread/thread/b5e643ef9aa33878/4e7a36c207aff0a6?q=Trattler+pupil&rnum=2#4e7a36c207aff0a6
Dr. Trattler posted:

"There is no question that pupil size is important in refractive surgery. There are major flaws in the studies that have come out recently.

1. The Schallhorn study had an insufficient number of large pupil patients to make any conclusions on the issue of pupil size and night time vision problems.

2. The Pop and Schallhorn studies have a major flaw in their study. They looked to see whether patients with pupils that are larger than the manufacturer's optical zone had night time vision problems. The problem is that they did not control for the level of myopia. This is critical, because according to Dr. Jack Holladay's article in JCRS 2002 "Topographic changes in corneal asphericity and effective optical zone after laser in situ keratomileusis" - the final functional optical zone for a patient shrinks with increased levels of myopia. So for every diopter of myopia of treatment, the final optical zone will be smaller than the Manufacturer's optical zone. I am sure this is confusing - but the key is that the articles have not shown that pupil size is unimportant - and therefore pupil measurements are important.

Bill Trattler, MD
Miami, FL"

Schallhorn, just like Slade, can't seem to make up his mind whether pupil size is important or not.


http://abstracts.iovs.org/cgi/content/a ... /45/5/2827

Investigative Ophthalmology & Visual Science

Higher order and spherical aberrations of anterior cornea surface before and after LASIK

S. Xu1, S. Schallhorn2, J. Laurent3 and A. Engle4
1 Ophthalmology, Refractive surgery center, San Diego, CA
2 Ophthalmology, Refractive surgery center,Navy Medical Center, San Diego, CA
3 Ophthalmology, Navy Medical Center, San Diego, CA
4 Ophthalmology, Navy Medical Center,Refractive surgery center, San Diego, CA

Abstract

Purpose: To investigate the higher–order (HO) and the spherical aberrations(SA) of the anterior cornea in normal myopic eyes before and after LASIK surgery.

Methods: Using the VOL–Pro program, corneal pupil zone HO rms and the Zernike coefficient of the SA ( Z40) before and after LASIK surgery were computed from the corneal Orbscan topographic maps of 108 myopic eyes (54 subjects). Subjects were 13 female and 41 male; mean age 35.4 ± 7.23; pupil sizes ranged from 4 to 8mm. Mean manifest preoperative spherical equivalent was –4.11±1.51 D (ranged –1.5D to –8.25D). Correlations between the aberrations and pupil size, manifest spherical equivalent (SE), uncorrected visual acuity (UCVA), best–corrected visual acuity (BCVA) and the subject’s responses to psycometric questionnaires were analyzed using Statistica 6.0.

Results: Post LASIK, the HO rms and the coefficient of the SA were increased in 88.0% (95/108) and 96.3% (104/108) of eyes, respectively. The Mean HO rms was 0.50 ± 0.5297µm preoperatively and 0.71± 0.3839µm postoperatively (P<0.001). The mean coefficient of the SA was 0.26 ± 0.1505µm preoperatively and 0.51± 0.3085µm postoperatively (P<0.0001). P value of the correlation between pre– and post–HO rms and SAs and pupil size, manifest SE and VA are listed:
Pupil size Pre–SE Post–SE UCVA BCVA
Pre–HO rms <0.001 =0.7447 =0.9563 =0.4714
Pre–SA <0.001 =0.1121 =0.8835 =0.1818
Post–HO rms <0.001 =0.0008 =0.0066 =0.1197 =0.5679
Post–SA <0.001 =0.00001 =0.0116 =0.1845 =0.5445

The preoperative SA was correlated with subject’s symptoms of glare and clarity, postoperative SAs correlated with haze, postoperative HO rms correlated with symptoms of glare and haze (P<0.05).

Conclusion: Anterior corneal HO rms and SA varied greatly among subjects and increased post LASIK which correlated with the pupil size and the degree of myopia. Higher order and spherical aberrations do not appear to affect the high contrast central visual acuity but do appear to affect the quality of vision.



Another important issue to consider with all of Schallhorn's studies is that he misuses the terms "glare" and "haze". As a matter of fact, the terms are widely misused by the industry, which has created a lot of confusion. They also misuse the term "loss of contrast sensitivity". Any HOA that degrades the retinal image will result in a loss of sharp, distinct images, which is what the industry calls loss of contrast sensitivity. It's not the same as loss of contrast sensitivity from cataract opacities.

Talking specifically about large pupils, spherical aberrations result in starbursts and halos around light sources and illuminated objects. This is not glare -- it's a degraded retinal image due to a multi-focal cornea -- the periphery is out of focus -- you have images that are refracted differently being superimposed on each other. The very same etiology is causing what the industry terms "loss of contrast sensitivity" -- a dark object against dark background which is degraded appears to have lost its edges and just blends into the background. Just like the headlight which scatters out into a starburst, the dark object against a dark background is also scattering making it hard to detect.

This is not haze and it's not glare and it's not loss of contrast sensitivity -- it's spherical aberrations caused by pupils dilating larger than the functional optical zone. And the reason that most patients experience these symptoms is because of a basic design flaw of lasers. Lasers were designed to treat flat surfaces -- the cornea is not flat, it's prolate. Only the very center of the cornea is being fully corrected. And the larger the pupil, the worse the problem. And then you have those patients with enormous pupils whose pupils actually dilate beyond the ablation zone, allowing light from the untreated cornea to reach the retina. Hello, if the light was defocused before LASIK, don't you think it's going to be defocused after LASIK if you didn't touch it with the laser?

Take a wavefront map of a patient with enormous pupils, and take the scan as large as the scotopic pupil, and then tell me that pupil size doesn't matter.