Daily wear contact
lenses
Daily wear contact lenses can be soft or rigid contact lenses made
of different types of plastic, depending on the specific type of lens. Daily
wear lenses are to be worn for periods of less than 24 hours at a time, and
should be removed each night before the wearer goes to sleep. Lenses generally
need to be replaced annually or biannually.
Extended wear contact lenses
Extended wear contact lenses are
usually soft contact lenses, but are designed to be worn for 24 hours or more at
a time. Some lenses are FDA approved for up to 30 days of continuous wear, but
most doctors recommend removing and cleaning the lenses at least weekly.
Extended wear lenses have replacement schedules that vary significantly by the
specific type of lens and length of continuous wear.
Disposable contact lenses
Disposable contact lenses are soft
contact lenses, either daily wear or extended wear, that are replaced on a 7 to
30 day cycle. Wearers generally purchase a supply of disposable lenses that will
last six months to one year.
Hard contact lenses
Hard contact lenses are made from a rigid
plastic resin, polymethylemethacrylate (PMMA). The lenses are more durable and
easier to handle than soft contact lenses, but many people may find them
uncomfortable. PMMA does not absorb water, and does not allow for the
transmission of oxygen through the lens to the eye. Hard contact lenses should
be removed daily.
Rigid gas permeable contact lenses
Rigid gas permeable (RGP)
contact lenses are made of a non-absorbent material that is oxygen permeable.
RGP lenses are durable and easy to handle like hard contact lenses, but more
comfortable to wear, though usually not as comfortable as soft contact lenses.
Most RGP lenses are used for daily wear, but some lenses can be worn for
extended periods of time.
Medically necessary contact lenses
Following certain surgeries,
soft contact lenses are sometimes prescribed to act as a replacement for the
front covering of the eye that has been removed or disturbed. These contact lens
prescriptions are medically necessary, and are generally addressed differently
than elective contact lenses in managed vision care policies. Medically
necessary contact lenses can also be prescribed for the treatment of certain eye
diseases, including keratonocus.
Toric lenses
Toric lenses are either hard or soft contact lenses
used to treat astigmatism, which cannot be corrected with traditional spherical
contact lenses.
Tinted contact lenses
Many soft and disposable contact lenses have
a visibility tint, usually bluish, that makes them easier to see. This
visibility tint makes the lenses easier to handle and easier to find if the
wearer drops them. There is generally no additional charge for lenses with a
visibility tint. Contact lenses can also be tinted to change or enhance the
color of the wearer's eye. The lenses are generally made with a clear center so
that the wearer's perception of color is not affected. Since these lenses are
more complicated to manufacture, they are generally more expensive than clear
contact lenses.