These lenses are most commonly used where the surface of the eye is irregular. This may be due to diseases such as keratoconus, or, procedures such as corneal transplant. You cannot achieve a clear focus with an irregular cornea, even with glasses. These contact lenses create a smooth surface and clear vision is restored.
Keratoconus and RGPs
One of the most common uses of RGP hard contact lenses is in the management of keratoconus. They are in fact the mainstay treatment for keratoconus. RGP lenses for keratoconus come in a range of designs:
These may be smaller or larger diameter, depending on the unique characteristics of your eye, but they only touch your cornea.
These are larger than corneal designs, and extend onto your sclera. This can greatly enhance comfort and provide better vision
These are the largest of all and only touch the white of your eye, completely vaulting the central (often very sensitive) surface of your eye. These used to be the lenses we turned to when all else had failed but they provide such clear, comfortable vision, they are often our lens of choice for a sensitive or very irregular eye.
Corneal Transplant and hard contact lenses
Sometimes, if the cornea has become scarred or can no longer provide clear vision, even with contact lenses, you may need a corneal transplant. Grafts are best avoided for as long as possible, but can be a sight-saving procedure when indicated. After a corneal graft, your eye will have an irregular surface and much clearer vision may be possible through the use of specialised RGP lenses.