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00034_Field_34.txt
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1997-10-29
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677b
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FITTING RIGID LENSES
Rigid lenses are fitted such
that the back curve of the lens
approximately matches the
shape of the cornea. There are
flatter curves in the periphery
of the lens to give some edge
clearance. The lens should stay
reasonable centered on the
cornea and move with a blink.
Sodium fluorescein is used to
visualize the tears behind the
lens and to determine the
clearance of the lens from the
cornea.
The fluorescein has to be illuminated with a blue (or UV) light source either from a hand held source or with the colbalt filter in the biomicroscope in order to obtain the fluorescence.