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00193_Field_193.txt
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1997-10-28
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21 lines
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.