| Silicone-Hydrogel Contacts | ||||||||||
 Contact lenses offer a great many advantages to patients who would rather
not wear glasses. Contact lenses can be the perfect solution for playing
many sports. For people who work outdoors in colder climates, contacts
don't "fog up" , like glasses can. For those with high optical
prescriptions, contacts can provide better overall vision and significant
cosmetic advantages.However, there is a very large issue with contact lenses that is not a factor with glasses...your eye needs oxygen. The cornea (the clear window forming the front of the eye) is a living tissue. To stay clear and healthy, the cornea needs a good supply of oxygen but it has no blood vessels of its own to supply it. The majority of oxygen required by the cornea must be drawn from the air in contact with the cornea. When you insert a contact lens, you're essentially placing a plastic "seal" over your cornea that can significantly reduce the amount of oxygen available. This is especially true if you sleep with contact lenses in place. Manufacturers of contact lenses have made significant developments in lens materials in recent years. A material creating a great deal of interest is a blend of silicone and the hydrogel material from which most soft lenses have traditionally been made . A "blended" silicone-hydrogel material transmits 7-8 times more oxygen to the cornea than a conventional hydrogel material does. Lower risk of eye infection Eyes starved of oxygen tend to develop problems. Studies have demonstrated that as  the
oxygen transmission of a contact lens material goes down, bacterial
binding to the cornea goes up...and with it, the risk of eye infection. This is because, when oxygen levels are reduced, the surface of the cornea can be compromised, thereby allowing pathogenic bacteria to bind to the corneal surface cells. Since silicone-hydrogel contact lenses transmit oxygen at high levels, they do not disturb the surface of the cornea or reduce the eyes' own ability to minimize bacterial binding. If bacteria can't bind to the eye then it can't infect the eye. One way to evaluate how well oxygen reaches the cornea through a contact lens is to monitor corneal swelling. If not enough oxygen is present, the cornea swells. Corneal swelling measured with silicone-hydrogel contact lens wear is often identical to swelling measured when no lens at all is being worn...a remarkable finding. Who is a candidate? The unique properties of
silicone-hydrogel contact lenses makes them an attractive option for all
patients. Silicone hydrogels are increasingly being used for daily,
flexible Silicone hydrogels are also finding a place as a therapeutic lens for a
range of conditions. The ocular health benefits of high oxygen
permeability combined with the comfort of a soft lens make silicone hydrogels an excellent choice
for wear as a "bandage lens". Silicone-Hydrogel "extended-wear" contact
lenses are a good
alternative to laser vision surgery for the many people who are not good
candidates for the procedure. The shape of their eyes, size of their
pupils or even the amount of vision correction required are all
contributing factors to whether a person is suitable for laser surgery.
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