The two main types of contact lenses are soft and rigid. As the names
indicate, it is how the material feels that separate the types.
Rigid, or hard contact lenses as
they are sometimes referred to, are not very flexible. They are usually
made with a oxygen permeable material that breaths well, allowing
oxygen to get to the cornea of the eye which important for the health
of your eye. The optics of the rigid lenses are very stable and will
generally provide superior vision under extreme varying environmental
conditions. The rigid lenses usually need to be replaced about every
2 to 6 years. The major downfall of the rigid lenses is comfort.
It can take the average wearer several months before they no longer
feel the lenses on their eye. Also, dust or dirt in the air, if
it gets between the lens and the cornea, can be very painful until
tears wash the substance away or you remove the contact lens and
rinse it.
Soft contact lenses are very flexible.
There are dozens of materials that soft contact lenses can be made
from. The materials very in their water content and the amount of
oxygen that can pass through them. Also, soft lenses differ in the
length of time they can be worn; daily wear, taken out at night,
versus extended wear, where you can sleep in them. Soft contact lenses
also have different replacement schedules, from replacing them every
day to replacing them every six months to a year. The most common
contact lens today is a two week disposable, where the lenses are
taken out at night and thrown away after two weeks of wear. There
is also a new contact lens material called silicon hydrogel that
allows up to seven times more oxygen to reach to cornea. These lenses
have varying wearing schedules from one week to one month of continuous
wear. There are some patients with health issues like diabetes who
would benefit from wearing the silicone hydrogel lenses on a daily
wear basis.
For patients with an astigmatism,
toric contact lenses may be needed. Toric contact lenses are also
made from the same types of materials as other soft lenses except
they correct for an astigmatism.
