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Home > Archive > Lasik Eyes Surgery > May 2005 > Gee, even LASIK surgeons think visual quality after LASIK is a problem
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Gee, even LASIK surgeons think visual quality after LASIK is a problem
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| Informer 2005-05-18, 11:47 am |
| http://www.crstoday.com/PDF%20Artic...505_nordan.html
Excerpt from the full text:
Measuring the Results of Refractive Surgery
We still need to improve quite a bit.
By Lee T. Nordan, MD
Now that improved keratorefractive surgery, phakic IOLs, and the surgical
correction of presbyopia are becoming popular topics of conversation, it is
time to reexamine a basic issue: testing the results of refractive surgery
with a Snellen chart. We all know that refractive surgery often reduces
contrast sensitivity, yet we persist in measuring postoperative visual
function with a test that was designed to measure refractive error and uses
only letters at 100% contrast. This practice is tantamount to building a
race car and timing its performance with a sundial. In other words, our
measurements are not very meaningful.
THE VISUAL FUNCTION INDEX
Background
A Regan or Pelli-Robson chart is essentially a Snellen chart, but its
letters progress from 100% to 12.5% contrast. Patients simply read the
lowest line of letters they can. In my experience, the 25% contrast line is
a good starting point, and variations in visual function become apparent at
the 12.5% contrast line. These tests are as easy to administer as a Snellen
test, and they have a definite endpoint. Measuring contrast sensitivity in
the clinical setting that results in a curve is essentially a waste of time;
a contrast sensitivity curve cannot be interpreted in an objective, concise,
clinically significant manner in order to allow comparison with a norm or
another eye's visual function.
In 1993, I edited The Surgical Rehabilitation of Vision.1 In that textbook,
I described the visual function index (VFI) and the surgical efficacy index.
At the recent Aspen Invitational Refractive Symposium (a great meeting, by
the way), Rick Baker, OD, a long-time friend and optometrist who works with
Stephen Slade, MD, reminded me of the VFI. He again posed the question that
I and many others have been asking for 15 years: Why are we still measuring
the results of refractive surgery with a Snellen chart and then resorting to
descriptive phrases such as "patients are happy"? Happy usually means that
the patient's visual function is poorer than desired, but he isn't
complaining . today.
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| Glenn - USAEyes.org 2005-05-18, 11:47 am |
| Recognition of any limitation is the first step to its resolution.
Many common problems with refractive surgery in the early years now
almost do not exist because the limitations were identified and the
best minds worked on the problems finding new methods of resolution or
avoidance.
Of course, there is no such thing as a perfect surgery. There will
always be room for improvement. There will always be risk. This is
something anyone considering refractive surgery needs to understand
and evaluate.
Glenn Hagele
Executive Director
USAEyes.org
"Consider and Choose With Confidence"
Email to glenn dot hagele at usaeyes dot org
http://www.USAEyes.org
http://www.ComplicatedEyes.org
I am not a doctor.
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| CatmanX 2005-05-18, 11:47 am |
| You can't fix a problem until you acknowledge its existence.
dr grant
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| Ragnar 2005-05-18, 11:47 am |
| I agree that the Snellen numbers are pretty useless, but most doctors
are only interested in treating the patient, not tracking the results.
That goes for glasses, contacts, and refractive surgery.
One comment about the article you mentioned... from Dr. Nordan. Dr.
Nordan either semi or completely retired a year or two ago. Since
then, he's been playing the role of backseat driver in the eye care
world. He never applied such rigid standards to his own practice.
On Tue, 17 May 2005 20:57:35 -0400, "Informer"
<Informer@Yahoo_nospam.com> wrote:
>http://www.crstoday.com/PDF%20Artic...505_nordan.html
>
>Excerpt from the full text:
>
>Measuring the Results of Refractive Surgery
>
>We still need to improve quite a bit.
>
>By Lee T. Nordan, MD
>
>
>
>Now that improved keratorefractive surgery, phakic IOLs, and the surgical
>correction of presbyopia are becoming popular topics of conversation, it is
>time to reexamine a basic issue: testing the results of refractive surgery
>with a Snellen chart. We all know that refractive surgery often reduces
>contrast sensitivity, yet we persist in measuring postoperative visual
>function with a test that was designed to measure refractive error and uses
>only letters at 100% contrast. This practice is tantamount to building a
>race car and timing its performance with a sundial. In other words, our
>measurements are not very meaningful.
>
>
>
>THE VISUAL FUNCTION INDEX
>
>Background
>
>A Regan or Pelli-Robson chart is essentially a Snellen chart, but its
>letters progress from 100% to 12.5% contrast. Patients simply read the
>lowest line of letters they can. In my experience, the 25% contrast line is
>a good starting point, and variations in visual function become apparent at
>the 12.5% contrast line. These tests are as easy to administer as a Snellen
>test, and they have a definite endpoint. Measuring contrast sensitivity in
>the clinical setting that results in a curve is essentially a waste of time;
>a contrast sensitivity curve cannot be interpreted in an objective, concise,
>clinically significant manner in order to allow comparison with a norm or
>another eye's visual function.
>
>
>
>In 1993, I edited The Surgical Rehabilitation of Vision.1 In that textbook,
>I described the visual function index (VFI) and the surgical efficacy index.
>At the recent Aspen Invitational Refractive Symposium (a great meeting, by
>the way), Rick Baker, OD, a long-time friend and optometrist who works with
>Stephen Slade, MD, reminded me of the VFI. He again posed the question that
>I and many others have been asking for 15 years: Why are we still measuring
>the results of refractive surgery with a Snellen chart and then resorting to
>descriptive phrases such as "patients are happy"? Happy usually means that
>the patient's visual function is poorer than desired, but he isn't
>complaining . today.
>
>
>
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