If you have keratoconus, Drs. Reto and Halscheid may recommend gas permeable contact lenses (also called GP, rigid gas permeable or RGP lenses). Since GP lenses are made of a non-pliable material, they retain their shape on the eye. Because of this feature, gas permeable contacts replace the irregular surface of a keratoconic cornea with a smooth, uniform surface to focus light and sharpen vision.
Sometimes an eye with keratoconus is too sensitive and unable to adapt to gas permeable lenses. In these cases, a contact lens fitting technique called “piggybacking” may be used. First the cornea is fitted with a soft contact lens, and then a GP lens is fitted over the soft lens. Because the soft lens acts like a cushion, piggybacking can make gas permeable contact lenses more comfortable for people with keratoconus.
Another option for keratoconus is hybrid contact lenses. These advanced lenses have a gas permeable optical center with a soft ring around it. For many wearers, hybrid contacts offer the clarity of GP lenses and wearing comfort that rivals soft lenses. Special hybrid lens designs are available specifically for eyes with keratoconus.
Still another contact lens option for keratoconus is scleral GP lenses. These large gas permeable lenses vault over the irregular surface of the cornea and rest on the white sclera of the eye. The large diameter of scleral lenses provides a more stable fit than regular gas permeable lenses on highly irregular corneas with keratoconus.
