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- Eye Care Treatment
- Eye Disease
- Lasik Surgery
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Cornea Topography - Technology To Study Your Cornea
A remarkable innovative technique called "corneal
topography" can generate a computer printout that shows the
curvature and the "hills and valleys" of your cornea. By studying
these brightly color-coded contour maps, your physician can diagnose
corneal shape abnormalities and monitor changes in the front surface
of your eye. A thorough understanding of the various elevations of
your eye's bubble-like window can help your doctor decide whether
you are a candidate for refractive surgery.
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If you decide to have LASIK, a specialist can
literally take "before and after" pictures that show
surgically-induced changes in your corneal topography. Used
in evaluating your results, these maps show the pre and
post-surgical dioptric (refractive) power of your cornea.
Rare complications usually can be easily pinpointed. For a
nearsighted person, such elevation "photos" should show the
flattening effect of the operation on the cornea.
To create topography maps of your cornea, high resolution
video cameras that are attached to a specially programmed
computer photograph your eye's front surface and profile.
Each half-diopter change in elevation, which has a different
light-focusing power, is represented by a different shade of
color. The steeper curvatures, or "hills," are colored in
warm shades of reds, oranges, and yellows while the flatter
"valleys" are cool shades of light and dark blue. |
The middle areas are green. In other words, the
steepest elevations with greatest refractive power are bright
red and the lowest elevations with the least dioptric power are
dark blue.
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Kept in your chart, these elevation maps
graphically illustrate the different refractive power of
many points on your cornea and most irregularities in its
surface. Corneal topography helps your doctor see how the
pattern of your astigmatism looks on paper. As you now know,
this refractive error is often caused by unevenness in the
curvature of the cornea's surface. Topographic maps may also
enable your physician to rule out subclinical keratoconus (a
cone-shaped steepening and thinning of the cornea that
causes irregular astigmatism). In addition, he can diagnose
subtle conditions with corneal topography that might be
missed with less sophisticated tests.
Your eye doctor will compare the astigmatism shown on your
corneal maps to the total refractive astigmatism that your
glasses correct. These measurements don't always agree. Some
astigmatism is caused by irregularities within the eye.
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Laser surgery corrects only corneal astigmatism. Hence, corneal
topography helps your doctor predict how much of your astigmatism
can be successfully treated with the laser.
Corneal maps also can help your doctor find the best contact lens
fit for you. A computer generated image of your cornea can quickly
"try on" many different types of contact lenses from the computer's
large database of soft, soft toric (for astigmatism), and rigid gas
permeable lenses without placing a single lens in your eye. |
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