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00044_Field_44.txt
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1997-10-29
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COMPUTERIZED VIDEOKERATOSCOPES
Limitations and Sources of Error: Instrument Design
The shape and size of the PlacidoΓÇÖs
disc pattern has an affect of the
accuracy and repeatability of the
data. Some instruments have used
a small pattern which is positioned
very close to the cornea (Tomey
Topographic Modeling System for
example). This small pattern allows
a large area of the cornea to be
covered by the reflected pattern
but results in more errors in
focusing and alignment.
A larger pattern (for example on the
EyeSys 2000 Corneal Analysis System)
minimizes the focusing and alignment
problems but may result in the nose
or brow blocking some of the pattern.