"Warpage" of the cornea refers to a distortion in the
shape of the cornea, usually due to the use of rigid
contact lenses, and especially poorly fitting rigid
lenses. The type of lens most notorious for this is the "hard"
type of lens, which is a non-gas-permeable lens made of a
plastic called PMMA. This type of lens is still used today
successfully by many people. However, the lens is known to
flatten out the cornea, often reducing or eliminating
astigmatism. When lens use is discontinued, the cornea
will try to spring back to its original shape. Thus, it
may be impossible to find a glasses prescription that will
consistently give clear vision for times when the contact
lens is not in. Often only the contact lens itself can
give clear vision. A condition known as "irregular
astigmatism" refers to an irregular curvature of the
cornea, usually caused by poorly fitting rigid lenses.
It may take several weeks of not using a contact lens for
the cornea to return to its normal curvature. At this time,
the proper fitting measurements can be made to determine
the shape of a contact lens needed which will not distort
the shape of the cornea.
