Silicone Hydrogel Contact Lenses
Silicone Hydrogel contact
lenses are the latest development in soft contact lens
materials. They are healthier than conventional soft lenses
because they allow up to 6 times more oxygen to pass
through them and increased oxygen transmission results in
better overall eye health. Advantages of silicone hydrogel
lenses over conventional soft lenses include: more resistance to
protein deposits, less drying of the lenses, lower risk of
eye infection, easier handling due to increased rigidity of
material, and much lower incidence of complications with
extended wear use (overnight wear). The convenience of 30
days continuous wear (PureVision and Focus Night & Day), as
well as the lowered incidence of eye health complications are
quickly making silicone hydrogels the most popular lens of
choice for both eye care practitioners as well as patients.
Most eye doctors believe that within the next 5 years, more
patients will be wearing silicone hydrogel lenses than any
other lens material.
The current brands of spherical silicone hydrogel lenses
available, in order of highest oxygen transmissibility to
lowest, are:
* Ciba Focus Night & Day which is approved for 30 day
continuous wear
* Vistakon's Acuvue Oasys which is approved for 2 week
daily wear use or 6 night extended wear and is designed to be
more wettable than the others and is therefore beneficial for
people who have dry eyes
* Ciba's O2 Optix which is approved for 6 days continuous
wear or 2 weeks daily wear
* Bausch & Lomb's PureVision which is approved for 30 days
continuous wear
* Vistakon Acuvue Advance which is a 2 week disposable
lens and has not yet been approved for extended wear.
There are also currently two toric (astigmatism
correcting) silicone hydrogel lenses on the market:
* Bausch & Lomb PureVision Toric is the only silicone
hydrogel toric lens available and is approved for 30 days
extended wear use
* Acuvue Advance For Astigmatism - currently approved as a
2 week daily wear lens
Studies have indicated that some lens care cleaning systems are
compatible with silicone hydrogels, while others may cause
adverse reactions due to toxicity. Aquify, Optifree
Express, and ClearCare multipurpose solutions have all been
FDA approved to be used with silicone hydrogels. AOSept has
proven to be an acceptable hydrogen peroxide based system to
use with these lenses. In some studies, Renu Multiplus has been
shown to cause an adverse corneal reaction when used with
some silicone hydrogel lenses (source Contact Lens
Spectrum, August 2005). Additionally, UltraCare and
SoloCare are not recommended for use with silicone hydrogel
lenses.
Most people would benefit from wearing silicone hydrogel lenses
as compared to conventional soft lenses due to the health
advantages, however, these lenses are especially useful in
the following types of patients: people with high
prescriptions; those whose eyes show signs that they require
more oxygen; wearers who experience end of day discomfort,
dryness, or redness with their conventional soft lenses;
people who wear their lenses for more than 12 to 14 hours a
day (including overnight wear); and kids and teenagers who
tend to routinely over wear their lenses. Additionally,
since the Focus Night & Day as well as the PureVision lenses are
approved for 30 days of continuous wear, they can be
considered as a useful alternative for people contemplating
refractive surgery.
Silicone hydrogels may not be the lens of choice for all
patients. These lenses are generally more expensive than
non-silicone lenses so a more price conscious consumer may
not prefer this option. Also, in some wearers, the silicone
material tends to attract more lipid deposits, which may
cause blurred vision and discomfort. There are some cases
where a patient is not able to adapt well to the more rigid
silicone material, which may result in some minor defects
to the corneal integrity. These complications are rare and
generally the health advantages and increased comfort that
most wearers experience far outweigh the incidences of
adverse reactions in those who do not adapt well to the
material.