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Keratom.DIr
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00193_Field_193.txt
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1997-10-29
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621b
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HOW THE KERATOMETER WORKS
The keratometer treats the cornea
as a convex mirror. A pattern,
called mires, of known size are
reflected off the cornea. The mire
pattern used with the keratometer
is a circle with plus signs on each
side in the horizontal meridian
and a line (minus sign) top and
bottom.
The mire pattern is formed by a
plate on the front of the keratometer
which is opaque except for the
transparent pattern which is illuminated
from behind by a mirror at a 45 degree
angle which reflects the light from the
bulb below the axis of the instrument.