This is Video 10
and a review of everything discussed throughout the video series
and it's intended to be and overview of
use with your Medmont E300 Corneal Topographer.
If you click on the patient name and the,'Clinical' tab,
you can enter the patient Spectacle RX if designing a
Rigid Lens from your Medmont Studio software.
With the, 'Home' icon, selected
you can,
capture Topography,
create new patients, delete patients,
you can link
specific maps
to third party software's.
With the 'Configure' option, you can
create specific
records
to relate your Medmont
to both,
the practice,
to patients,
creating new fields, specific to the patient,
you can calibrate your instrument
with this function.
These functions are used very infrequently generally setup in the
beginning
and the only one you're going to refer to
on a more
routine basis it might be the Calibration, which should be done
every six months,
or if you move your
Medmont.
If we click on a map
we have a number of
functions
available here.
The first
allows us to change the patient
if this map were
saved to the wrong patient file, we can change it here. If
this is not a left eye but rather a right eye, if it was incorrectly captured,
we can change it on this window.
The main function is your 'Image' button,
and this allows us to view from one to four different map simultaneously,
and it's used most frequently.
Your third function is your, 'Comparison' map,
and this allows you to compare two instances in time,
a
Pre Orthokeratology and Post Orthokeratology, or
a
patient
last year's visit,
and this year's visit, to see if there's any change in disease progression.
The next function is your, Combination, which allows you to view the map a
number of different ways.
This function maybe most valuable
in looking at the
Photokeratoscope Image.
Looking for the quality of the Placido Reflection,
Eyelash Shadows,
measuring Visual Iris Diameter,
Pupil size, these type of options.
Lets click back on the main image
option,
and review some of the other analysis
options available to us.
If you click on,
'Analysis',
this allows us to look at the details of
this particular exam or multiple exams.
We can change the axis that it's analyzed on, generally it defaults to the,
'Flat',
the Flat Meridian.
We can change or set the chord
of measure, meaning,
what diameter do we want to measure our information to.
We can look at the 'Flat' Meridian or the 'Steep, Meridian.
This is helpful when looking at
Sagittal Depth for instance.
We measure the Sagittal Depth of this eye as 1453 on the, 'Flat' and
1576 on the 'Steep',
approximately,
a 123 Microns difference exist between
the Flat Meridian and the Steep Meridian.
This tells us that
this patient me require a Specialty Lens
because there is greater than 50 Microns
difference between the Flat and Steep Meridian.
We could look at the, 'e2 Values',
e2 being
in negative, indicating an Oblate Shape, so across the Flat Meridian
this
Pellucid Marginal Degeneration Eye,
has an Oblate Shape across the Vertical or the Flat Meridian.
On the Steep Meridian or the Horizontal the Cornea is a positive e2 Value,
or Prolate.
Oblate being
flattest in the center, steepest in the periphery.
Prolate being steepest in the center, flattest toward the periphery.
Let's close this window down
and we can look at the, 'Display' option.
Presently we have 'Axial Power' displayed. Axial is the best way to
interpret
the type of Astigmatism, be it,
Against the Rule, With the Rule.
In this case we can see clearly an, Against the Rule,
Corneal Astigmatism.
Is it regular or irregular, an Axial map helps us to understand that,
and although there is a defined, Steep and defined
Flat Meridian,
this Pupillary Zone looks
slightly asymmetrical on this Pellucid Marginal Degeneration patient.
If we were
curious where the steepest point of curvature, is we could
select our, 'Tangential' map and see that the
point of most radical steepening is inferior.
The point of most radical curvature change
toward the flatter side
is this deep
blue area.
If we were curious about which is the highest or lowest point on the eye,
we could select our, 'Elevation' map.
Elevation map drops a perfect sphere on top of the topography
and looks at whether the Cornea is above the sphere or below the sphere.
With the white axis line running vertically we can see
the dotted section of the line corresponding here,
with the dotted section of the line on the graph,
and the elevation of this eye goes beyond
the graph. In other words, the
Corneal Elevation here, is much higher than the Spherical Surface.
This is a high point on the Cornea,
this point here
is also a high point on the Cornea, in relationship
to the Spherical Surface.
However; horizontally
we can see by these
blue areas we have a
low point in Corneal Elevation. If we were to drop a Ridged Lens on this eye
it would
lift at three and nine o'clock,
it would bear at twelve and six o'clock.
Also on, Display',
we can change
anyway we analyze these eyes.
We could reduce the Color Map Opacity, to see more Ring Reflection,
or increase the Color Map Opacity to eliminate it.
We could
eliminate the image so just the colorized Topography exists,
we can get rid of the
'Annotations', 'Cross-Section', and
the 'Attributes'.
So you can change
the way your maps appear
using the, 'Display' and
changing these options
anywhere on this,
on this screen.
You can click on, 'Perspective'
and change to a three-dimensional view,
and
if you right click and select the, 'Pan' tool,
you can observe the
Corneal Curvature in 3D
along
the entire surface area.
This is helpful for patients in appreciating
distortions in there eye or
Astigmatism in their eye.
We'll go back to a two-dimensional image,
and right click, select the
pointer,
under the,
'Attributes' window, we can look at disease detection indices.
Before we do so
let's just look at
the main part of the window, the
Corneal Stigmatize and for this patient is measured as 10.5 Diopters.
This is an exceptionally
high Corneal Astigmatism.
We see a very flat, Flat K, and steep, Steep K.
Having the Flat K Axis,
Against the Rule, axis 102,
may be a good indication with the high Corneal Astigmatism,
and the Asymmetrical
appearance of the image,
that this is a Pellucid Marginal Degeneration patient.
We can look at the, Eccentricity Values,
when dealing with diseased eyes they tend to have higher Eccentricity Values.
Normal Eccentricity is .65.
This patient is very close to norm in terms of Eccentricity,
but certainly abnormal in terms of Corneal Astigmatism,
and Against the Rule,
along with the appearance of the map
showing the,
Kissing Doves, or Butterfly Wings as Pellucid is often described
in Corneal Topography
would indicate that this is a
diseased eye.
We could also look at the scale range and we go from
33 Diopters on the flattest we can read,
to 48 Diopters the steepest the Topographer can read,
a scale range of
15 Diopters, normal Cornea falls within
10 Diopters, so this is an abnormal eye.
We could look at the, 'IS' Value and
Corneas with,
Inferior Corneas steeper than
1.5, or in other words,
if the IS Value is greater than 1.5,
that is indicative of the diseased or asymmetrical eye.
In this case
the Topographer is telling you the Inferior Cornea is
steeper, on average, than the Superior Cornea,
by approximately 5.98 Diopters.
We could look at the, Surface Asymmetry Index, and look at these Oblique
Meridians.
Is this Hemi-chord
similar to this Hemi-chord?
If not the Surface Asymmetry Index
will be higher than normal.
The same thing along this axis.
So the more asymmetrical
one side is as compared to the other, and the opposing
Oblique Meridian, if
the Surface Asymmetry Index is greater than 1.0,
that would be indicative of a diseased or Asymmetrical Eye.
Last value, Surface
Regularity Index, looks at the power distribution within the pupil.
The greater the distribution of power
the more asymmetrical
the eye the greater the likelihood
of disease.
The threshold for
abnormal would be greater than .8.
If we were wanting to
design a contact lens for this patient
we might go to the, 'Home',
and, 'Contact Lens'.
Then select from are available lens designs
the appropriate trial lens that we would like to diagnostically fit.
We then enter the Spectacle RX if it weren't already entered on the patient window
and say, 'Okay',
and this brings up Contact Lens Design Window.
The first thing you might do is
pick up the contact lens and put it on the Geometric Center of the Topographer.
If the maps weren't geometrically captured.
Next we might chose
the appropriate
Lens Diameter.
In this case a 10.2.
Next step is click your cursor in the center of the Topography and determine
the Tear Film Thickness.
With the present Base Curve we have a Tear Film Thickness of 37
Microns.
We desire somewhere between 30 and
40 for a diseased or asymmetrical eye.
In a normal eye we want around 20 to 25.
Since we have 37 we will consider this a healthy amount Apical Clearance.
Next will drag this white axis line
to the meridian with the greatest bearing, so observing the graph down
below,
which axis does the lens appear to the land at
on two opposing sides?
In this case at twelve o'clock,
dotted section of the line here corresponding dotted here,
and at six o'clock
solid section of the line corresponding here.
So zero would be the corneal surface
we can see our contact lens lands at this point
then up to Apical Clearance
lands at this point. Then
which axis has our highest lift
along the Horizontal Meridian, or Steep Meridian,
we appear to have a
significant amount of
pooling at
nine o'clock
and three o'clock.
This lens would be
horribly unstable across that Horizontal Meridian with such significant clearance
at three and nine o'clock.
With are bearing at twelve and six o'clock
the lens will not want to have a superior
positioned lid attached
type of alignment with good movement
with the blink, good Tear Pump.
You would have
movement along the Horizontal Meridian, possibly a positioning of the lens
significantly Nasal or Temporal.
So you can
determine which contact lens parameter would be ideal for the eye.
In this case
a Scleral Lens maybe
best suited for this patient with
such a symmetry,
and such a Steep Horizontal Meridian.
A Piggyback might be another option as well.
This concludes
Video 10 on The Review of
Functions and Usage with your Medmont E300 Corneal Topographer.