CORNEAL SENSITIVITY MEASUREMENT 
             WITH THE COCHET-BONNET AESTHESIOMETER

The Cochet-Bonnet aesthesiometer 
actually measures the corneal touch 
threshold (inverse of the sensitivity) 
with a variable length nylon filament.  

The end of the filament is brought up 
against the corneal surface with a 
force that just gives a noticeable 
bend to the filament.  The patient is 
asked to indicate when they feel the 
probe.  The test is started with longest 
filament possible since the long 
filament will give the least pressure 
as it bends very easily.  If the patient 
does not feel the filament, it is shortened in 0.5 cm steps until it is felt. There should be four to eight touches at each length.  When at least 50% of the touches are felt the test is completed.  The length of the filament is noted and using the conversion chart supplied with the instrument, the reading can be converted into mg./sq. mm.