Hydrogel lenses are made relatively large in diameter, usually 13.5 to 14.5 mm in diameter which results in the lens edge being beyond the limbus on the sclera.
It is necessary to use these
large diameters to keep the
lens centered and to provide
comfort. Hydrogel lenses are
comfortable due to being large
in size rather than being soft.
Most of the sensation from a
contact lens is due to the
eyelids hitting the edge of the
lens, not from the cornea.
Since these lenses are soft and flexible, not as many back curve variations are required to fit a wider range of eye shapes as is required with rigid corneal lenses.
