Silicone Hydrogel 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:
There are also currently two toric (astigmatism correcting) silicone hydrogel lenses on the market:
- 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.
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.
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Focus Night & Day were the subject of a three year study by Alcon.
The company reported that the performance of this silicone hydrogel (SiHy)
contact lens indicated that wearers enjoyed improved corneal health and
reduced frequency and symptoms of contact lens related eye health symptoms.
In particular, the study of 317 patients showed that Focus Night & Day
wearers had less problems with red eye, reduced dryness (22%) and
neo-vascularization (the development of new blood vessels in the cornea)
was reduced by 13%. During the first 8 months of 2005, Silicone Hydrogels
represented 24% of all soft contact lens sales – more than double the figure
for the same period of 2004. Ciba lenses represented almost 50% of silicone
hydrogel sales during this time.
Bausch & Lomb (manufacturer of Purevision, Purevision Toric and
Purevision Multifocal contact lenses) reported that 40% of new
contact lens fits are now silicone hydrogel contacts. They claim that
94% of wearers of their sector leading Soflens 66 Toric contacts can be
migrated to the Purevision Toric lens without a script change.
Vistakon, manufacturer of the Ultra-Comfort series of contact lenses
which comprises the Acuvue Advance, Acuvue Advance for Astigmatism and
the Acuvue Oasys says their silicone hydrogels are all addressing the
issue of end-of-day comfort for contact lens wearers. Prescription
parameter ranges are being expanded for each of these lenses (most
recently, plus powers for Oasys were made available). Acuvue Oasys
was also recently given FDA approval for up to 7 days of continuous
wear. Vistakon claims to have the number one silicone hydrogel with
their Acuvue Advance and the number one new-wearer toric in the Advance