![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 00 called Title)](gifs/SIGGRAPH96ET/ETs00_Title.jpg) |
(Title Screen)
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 01 called Neha)](gifs/SIGGRAPH96ET/ETs01_Neha.jpg) |
At the University of California at Berkeley, the OPTICAL project is a
multidisciplinary effort in the Computer Science Division and School
of Optometry.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 02 called Acronym)](gifs/SIGGRAPH96ET/ETs02_Acronym.jpg) |
"OPTICAL" is an acronym for "OPtics and Topography
Involving the Cornea And Lens". This project is concerned with the
computer-aided measurement, modeling, reconstruction, and
visualization of the shape of the human cornea, called corneal
topography.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 03 called NehasEye)](gifs/SIGGRAPH96ET/ETs03_NehasEye.jpg) |
The cornea is the transparent tissue covering the front of the eye.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 04 called LabeledCornea)](gifs/SIGGRAPH96ET/ETs04_LabeledCornea.jpg) |
It performs 3/4 of the refraction, or bending, of light in the eye,
and focuses light towards the lens and the retina. Thus, subtle
variations in the shape of the cornea can significantly diminish
visual performance.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 05 called ContactLenses)](gifs/SIGGRAPH96ET/ETs05_ContactLenses.jpg) |
Eye care practitioners need to know the shape of a patient's cornea to
fit contact lenses,
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 06 called Surgery)](gifs/SIGGRAPH96ET/ETs06_Surgery.jpg) |
to plan and evaluate the results of surgeries that
improve vision by altering the shape of the cornea,
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 07 called Keratoconus)](gifs/SIGGRAPH96ET/ETs07_Keratoconus.jpg) |
and to diagnose
keratoconus, an eye condition where the cornea has an irregular shape
with a local protrusion, or "cone", which has dramatic effects on
vision.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 08 called ThreeReasons)](gifs/SIGGRAPH96ET/ETs08_ThreeReasons.jpg) |
(Summarized reasons why eye clinicians need to know the shape of patients' corneas)
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 09 called BrianWheeledUp)](gifs/SIGGRAPH96ET/ETs09_BrianWheeledUp.jpg) |
Recently, instruments to measure corneal topography have become
commercially available. These devices, called videokeratographs,
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 10 called Measurement)](gifs/SIGGRAPH96ET/ETs10_Measurement.jpg) |
typically shine rings of light onto the cornea and then capture the
reflection pattern with a built-in video camera.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 11 called Videokeratograph)](gifs/SIGGRAPH96ET/ETs11_Videokeratograph.jpg) |
Instead of allowing
the videokeratograph to process the pattern,
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 12 called VKCloseUp)](gifs/SIGGRAPH96ET/ETs12_VKCloseUp.jpg) |
we at the OPTICAL project
extract the data and
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 13 called MeasReconModelVis)](gifs/SIGGRAPH96ET/ETs13_MeasReconModelVis.jpg) |
construct a mathematical spline surface representation from these
reflection patterns,
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 14 called Reconstruction)](gifs/SIGGRAPH96ET/ETs14_Reconstruction.jpg) |
as is described in our SIGGRAPH '96 paper. In
addition to developing this novel modeling algorithm, we are exploring
new scientific visualization techniques to display the resulting
information in an intuitive and accurate manner.
This video compares
our new visualization methods with an existing technique.
Using our modeling and visualization software, we will first show real
keratoconic data and then a simulated keratoconic model.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 15 called Visualization)](gifs/SIGGRAPH96ET/ETs15_Visualization.jpg) |
The most popular display of corneal topography is called the "corneal
map". This is similar to a topographic map where equal values of some
parameter are displayed in the same color.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 16 called AxialPower)](gifs/SIGGRAPH96ET/ETs16_AxialPower.jpg) |
The usual parameter that is
displayed is called axial power. However, as we will show, this can
produce misleading results.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 17 called GaussianPower)](gifs/SIGGRAPH96ET/ETs17_GaussianPower.jpg) |
We are proposing a pair of alternative
parameters that overcome this problem: Gaussian power, which is
related to the geometric mean of the minimum and maximum curvatures at
each data point,
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 18 called Cylinder)](gifs/SIGGRAPH96ET/ETs18_Cylinder.jpg) |
and cylinder, related to the difference between the
maximum and minimum curvatures at each data point.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 19 called ModellingWireframe)](gifs/SIGGRAPH96ET/ETs19_ModellingWireframe.jpg) |
We compute the
values of these parameters using our reconstructed spline surface
model.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 20 called BrianWheeledUp)](gifs/SIGGRAPH96ET/ETs20_BrianWheeledUp.jpg) |
Let's look at the corneal data from the patient we saw being
measured earlier.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 21 called BBAllNothing)](gifs/SIGGRAPH96ET/ETs21_BBAllNothing.jpg) |
His cornea has a cone in the lower right (our left).
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 22 called BBAllAxialPowerOnly)](gifs/SIGGRAPH96ET/ETs22_BBAllAxialPowerOnly.jpg) |
The top two
corneal maps show axial power,
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 23 called BBAllAxialGaussLabel)](gifs/SIGGRAPH96ET/ETs23_BBAllAxialGaussLabel.jpg) |
and the bottom maps show Gaussian power.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 24 called BBAllRegularBoxed)](gifs/SIGGRAPH96ET/ETs24_BBAllRegularBoxed.jpg) |
The left pair shows regular fixation where the patient is looking
directly into the videokeratograph.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 25 called BBAllConicBoxed)](gifs/SIGGRAPH96ET/ETs25_BBAllConicBoxed.jpg) |
In the right pair, the patient
has shifted his gaze up toward his left so that the cone aligns with
the center of the videokeratograph; we call this conic alignment.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 26 called BBAllAxialArrows)](gifs/SIGGRAPH96ET/ETs26_BBAllAxialArrows.jpg) |
As we compare the two representations, we note an important
difference: For different gaze directions, the shape and values of the
cone region as depicted in the axial power maps differ
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 27 called BBAllAxial5778Circled)](gifs/SIGGRAPH96ET/ETs27_BBAllAxial5778Circled.jpg) |
(for example,
the values at the cone center are 57 and 78 Diopters)
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 28 called BBAllWithAllCircled)](gifs/SIGGRAPH96ET/ETs28_BBAllWithAllCircled.jpg) |
but remain
invariant with our Gaussian power map. In other words, by simply
changing the direction of the patient's gaze, axial power yields two
conflicting descriptions of the cone whereas our proposed
visualization does not have this problem.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 29 called ModelWithoutConus)](gifs/SIGGRAPH96ET/ETs29_ModelWithoutConus.jpg) |
Now let's look at a simulated cornea. These four windows all display
the same keratoconic model. The upper left animation indicates how we
scale and move the cone around, while the other images show corneal
maps displaying different parameters. Axial power is shown in the
upper right, Gaussian power in the lower left, and cylinder in the
lower right.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 30 called ModelConus15Deg)](gifs/SIGGRAPH96ET/ETs30_ModelConus15Deg.jpg) |
The model of our simulated cone is rotationally symmetric, and
maintains a constant shape when moving across and around the
cornea.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 31 called ModelConus0Deg)](gifs/SIGGRAPH96ET/ETs31_ModelConus0Deg.jpg) |
Our two new visualizations faithfully represent the symmetry
and shape invariance.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 32 called ModelConusNeg20Deg)](gifs/SIGGRAPH96ET/ETs32_ModelConusNeg20Deg.jpg) |
However, axial power fails on both accounts,
erroneously showing the cone region as significantly changing shape as
it moves around and across the cornea, which is what we saw earlier.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 33 called MeasReconModelVis)](gifs/SIGGRAPH96ET/ETs33_MeasReconModelVis.jpg) |
This video has shown how the OPTICAL project is developing new
computer aided cornea modeling and visualization techniques to enable
eye care clinicians to help people overcome some of their difficult
vision problems.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 34 called Credits0)](gifs/SIGGRAPH96ET/ETs34_Credits0.jpg) |
Roll credits.
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![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 35 called Credits1)](gifs/SIGGRAPH96ET/ETs35_Credits1.jpg) |
![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 36 called Credits2)](gifs/SIGGRAPH96ET/ETs36_Credits2.jpg) |
![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 37 called Credits3)](gifs/SIGGRAPH96ET/ETs37_Credits3.jpg) |
![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 38 called Credits4)](gifs/SIGGRAPH96ET/ETs38_Credits4.jpg) |
![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 39 called Credits5)](gifs/SIGGRAPH96ET/ETs39_Credits5.jpg) |
![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 40 called Credits6)](gifs/SIGGRAPH96ET/ETs40_Credits6.jpg) |
![(1996 Siggraph Electronic Theatre OPTICAL Visualization Scene 41 called Credits7)](gifs/SIGGRAPH96ET/ETs41_Credits7.jpg) |
An inside joke. We found it funny.
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