subject: Optional Treatments For Keratcononus - Hybrid Lenses [print this page] Contact lenses, in particular Rigid Gas Permeable (RGP) contact lenses, are the most common form of vision correction for individuals that have the eye condition Keratoconus. If these RGP lenses are not working out for you then it may be that a hybrid contact lens is the answer.
Keratoconus is a disease of eye in which the cornea, which is the front part of the eye through which light enters, thins and distorts outwards into an irregular 'conical' shape.
It is this distortion that causes the poor eyesight. This is because the light coming into the eye is scattered and can not be focused onto the retina correctly. This results in blurred vision and ghost images .
Glasses and soft (or hydrogel) lenses may work for early or mild forms of the disease. In the more advanced cases the Rigid Gas Permeable lens is more effective. This is because it keeps its own regular shape and a layer of tears forms underneath it, between the cornea and the contact lens. The combination forms and artificial single surface that acts like a regular shape cornea. The size of the Rigid Gas Permeable lens means that the inner surface of the eyelid can rub against the edge of the lens causing soreness or irritation.
Additionally the lens can become dislodged from the eye very easily, especially if the cornea has become steeply distorted..
if this kind of soreness caused by the edge of the lens is a problem then a possible solution is the hybrid contact lens. The Rigid Gas Permeable lens is a lot smaller than a hydrogel (soft) contact lens. A hybrid contact lens is a combination of an RGP lens in the center with is then surrounded by a layer of hydrogel material around the outside.
Because the centre of the lens, the bit that goes over the cornea, is rigid it will maintain its own shape, trap the layer of fluid and form the single regular surface required for light to pass into the eye without being distorted. The hard edge of the rigid lens is softened by the hydrogel material and this reduces the sensation of the lens rubbing on the inner surface of the eye lid.
If you are struggling to deal with the sensations of wearing an RGP lens then a hybrid solution may be an effective option. Additionally they have less of a tendency to become dislodged and lost, and they may prove to offer greater comfort to people with dry eyes. They're not as easy to fit and remove as the Rigid Gas Permeable lens, and they tend to be more expensive.
by: Ralph Goldsmith
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