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The
Wrong Diagnosis - Anna's Story Part II
Kristy,
Anna's mom, talks in detail about the topos and data used by Anna's
doctors to diagnose her wth Keratoconus.
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Anna's
Topo's January 2004
The original scans that were used in diagnosing Anna
with Keratoconus
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Kristy:
Above are the topos from the OD that were used to originally
diagnosis Anna. When you compare these topos with ones from
Dr. Sindt, you can see some differences. The astigmatism does
look a bit more irregular on these but even so, if you were
trained, it shouldn't have been alarming! A visual exam should
have ruled it out!!! This doctor explained the topo as being
irregular and having "hot spots". The glasses he
prescribed her made her vision worse instead of better. As
a result, he felt the Keratoconus might actually be worse
than he had first thought. So this is when we went to a corneal
specialist, who we were told would be able to tell us the
exact level and nature of Anna's Keratoconus.
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Anna's
Topo's March 2004
By The corneal specialist who diagnosed Anna with Advanced
Keratoconus
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Kristy:
Above are the scans from the corneal specialist. Note that these
are only axial maps. This was all that the office gave me when I
called and asked for Anna's records. When I called and complained
about this, they told me this was all they had on file. I don't
know if they had originally done more scans or not but this is all
they had in her medical records upon request. Notice that there
are no elevation maps. I was later told it was a grave mistake to
diagnose Keratoconus using axial maps alone. They do not show corneal
thickness, only the rate of change. They show astigmatism but they
don't show the cause. Many doctors see a lot of red and automatically
think it's KC. I later learned that this is the wrong way of thinking,
as the red simply means a faster rate of change but it doesn't mean
thinning. At the end of the day, Keratoconus is about corneal thinning.
Ultimately, any diagnosis must be based on detecting and demonstrating
that thinning is the cause of the astigmatism.
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Orbscan
topographies made by Dr. Sindt
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Kristy:
Notice that the top left and right images are axial maps just
like the ones the other doctors obtained. But notice now the
red is more regular and in a bowtie configuration. The most
important maps are the elevation maps which Anna's other doctors
never did. To make an accurate diagnosis of Keratoconus, you
need to in addition, look at the elevation maps from the topography.
Elevation maps take a best fit sphere. It is similar to a best
fit line. An elevation map will show the bump on the cornea.
The high points will show up as red and the low points will
show up as blue. It tells you the thickness and reveals any
thinning.
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Pentacam
Images
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Kristy:
The pentacam is the most revealing of all scans. It shows
the cornea from every possible angle and shows whether or
not there is thinning. This scan was truly amazing. The above
example shows a cross section of the cornea! So even a layman
would be able to tell if there was any thinning. Dr Sindt
showed me some examples of scans with advanced Keratoconus
and you could see the thinning immediately. It's just like
looking at an archway accept the arch is actually your cornea!
It's truly an incredible machine. But its cost exceeds the
resources of most doctors and therefore is not very commonly
found in most doctors' offices. Below are Anna's Pentacam
maps taken by Dr Sindt.
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Kristy:
Dr Sindt spent a long time explaining to me how to read
the pentacam images as there is a lot of data to try and understand!
An important number is the one I have circled in red on both
maps. This number represents the thinning part of the cornea.
An average healthy cornea is around 550. In Anna's left eye
526 and her right eye 506. Because both thicknesses are below
the normal (although not significantly) Dr. Sindt was careful
not to rule out Keratoconus beyond a shadow of a doubt, however,
she was in no way certain that Keratoconus was present either.
Very early stages of Keratoconus can be difficult to diagnosis.
Kristy:
Dr. Sindt's diagnosis was so different than the other doctors,
who all labeled Anna as a little girl of 5, with Advanced Keratoconus.
Dr. Sindt went on to explain to me just how misleading an axial
map can be. All a patient has to do is have their eye slightly
off center and you get a false reading. If you're not looking
exactly central when the axial scan is taken, your map will
show irregular astigmatism. Just look up slightly and the reading
is false. She went further and said that even irregular astigmatism
is not automatically Keratoconus. Likewise it's possible for
a person to have normal bowtie-shaped astigmatism on an axial
topography and yet still have Keratoconus. There is no way you
can accurately diagnose Keratoconus with axial maps alone. The
thickness of the cornea has to be measured. All you read with
an axial map is rate of change and I think some doctors have
got into the habit of seeing a lot of red on an axial map and
automatically labeling it as Keratoconus. One of the doctors
went so far as to say Anna had visible signs of thinning. This
statement would mean that Anna was at the most advanced stages
of Keratoconus and requiring a transplant. Looking at the true
thickness of Anna's corneas, we now know that this is not the
case. Although Dr. Sindt used some very sophisticated equipment
on Anna, such as the pentacam, Anna's true diagnosis could have
been made with the equipment that all of her previous doctors
had in their office. They all had orbscans and they all would
have been able to have done elevation maps. It was never a question
of them lacking equipment. It was a question of them not knowing
how to use it and read the results correctly. I cannot put into
the words the stress and worry Anna's initial diagnosis of Advanced
Keratoconus put on our family. It all could have been avoided
if the doctors who examined her knew how to read a topography
accurately. |
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