Silicone Hydrogel Contact Lenses and Keratoconus
Treating keratoconus can often involve many different methods throughout a patient�s life. A common method early in the treatment of keratoconus is through the use of contact lenses, including silicone hydrogels. Silicone hydrogel contact lenses are contact lenses made of a substance that is super-permeable to oxygen and yet made of a soft flexible substance, known as silicone hydrogel.
For patients with keratoconus, fitting a contact lens can be difficult, silicone hydrogels can often be an important part of the fitting process. In progressed cases of keratoconus, the cornea has become thin to the point where it bulges outward. A contact lens must be fit around this bulge and still maintain proper fit, comfort, centration, and acuity.
Standard rigid gas permeable contact lenses are the simplest fitting choice and are often able to achieve success in early or mild cases of keratoconus. Because of the spherical shape, rigid gas permeable contact lenses provide clear vision when fitted correctly. A rigid gas permeable lens will fit over top the �cone� caused by keratoconus, allowing clear vision.
Piggyback contact lenses requiring a rigid lens and a silicone hydrogel lens are occasionally used to correct keratoconus. At times, a rigid gas permeable contact lens can be uncomfortable, especially for someone with keratoconus. Sometimes a hard contact lens is also unable to remain centered correctly to provide good vision for someone with keratoconus. In these cases, it is occasionally necessary to use two contact lenses simultaneously. A soft lens, often a silicone hydrogel, is placed directly on the eye. This silicone hydrogel lens can provide greater comfort and give a platform for the rigid lens to sit more accurately. A second lens, a rigid gas permeable contact lens, is then placed on top of the soft lens to help maintain the shape further and improve visual acuity further.
The silicone hydrogel lens is important because of its great capacity to allow oxygen to reach the cornea. A standard soft lens would reduce the amount of oxygen that arrived at the cornea causing hypoxia, a unintended side effect that could hasten the onset of keratoconus. A silicone hydrogel lens can provide up to six or seven times the oxygen transmissibility as a standard soft contact lens made of another plastic polymer. The silicone hydrogel is therefore a much safer lens for use with keratoconus.
While silicone hydrogel lenses with a rigid gas permeable can often provide many years of good vision, many patients with keratoconus will eventually require further treatment or may desire a surgical treatment that might allow them more freedom from contact lenses. Turner Eye Institute can provide these other options to assist patients with keratoconus.