Copyright 2007 www.eyes-and-vision.com
The
next-generation of hard lenses were known as gas permeable
lenses. And the lenses were not actually called "hard" anymore,
they changed the name to "rigid" to refect the flexibility of the new
lense's material.
Contact Lenses: Rigid Gas Permeable Type
Really the only problem with these lenses is
that while they can absorb a bit of moisture, it's still generally not
enough. Hence gas permeables tend to dry out and become
uncomfortable by the end of the day. They are a good choice if
you aren't happy with the vision clarity provided by soft contacts,
and/or are worried about possible infection more frequently associated
with soft lenses.
Although they resembled the old style hard lenses, they were light years ahead in the comfort department. Gas permeables allowed the cornea to "breathe"
by letting in oxygen and allowing carbon dioxide to escape. They
could also absorb small amounts of fluid, and weren't as vulnerable to
bacteria as soft lenses. The secret of the new lenses was the
addition of silicone to the len's surface area.
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