LENS POWER



For spherical contact lenses the power 
is specified in diopters just as with 
spectacle lens powers.  The lens power 
for RGP lenses can be measured on a 
lensometer just as spectacles, the lens 
is held against the lens stop.  Hydrogel 
lenses require that the water be blotted 
off the surface before measuring them 
in the same way.