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.