Soft Contact Lenses
Very mild cases of keratoconus can often be treated successfully using regular soft contact lenses. This is because in mild disease, the cornea has not begun to bulge significantly.
RGP (Rigid Gas Permeable) Contact Lenses
These lenses (also known as hard contact lenses) are not as flexible as soft lenses. They are usually used to correct the greater amounts of astigmatism or corneal irregularities present in keratoconus, giving better vision than either glasses or soft contact lenses. Using small-diameter specialised RGP lenses, approximately 60% of keratoconic corneas can be successfully fitted in the long term. What is critical is that your optometrist has multiple trial sets at their disposal. No two keratoconus corneas are alike.
So that leaves the 40%… This is where things can get tough. What do we go to next, if the small diameter RGPs fail?
Larger diameter RGPs
Larger lenses up to 11mm in diameter are often useful if stability cannot be achieved or if centration is poor with the smaller diameter lenses. Learn more about RGPs here.
If RGP lenses are not well tolerated, a popular option is to piggyback the RGP lens onto a soft lens. Usually the primary reason RGPs fail is because they are too uncomfortable. Occasionally, even in the best hands, the patient is just too sensitive. Piggybacking the RGP on a soft daily disposable can be the difference. That is assuming the soft lens can drape the cornea successfully. By introducing a piggyback system with an RGP lens, success can increase by up to another 20%.
Unfortunately if the keratoconus is beyond moderate, other contact lens designs may be required, including hybrid lenses. These have a rigid centre with a soft skirt. They have a long history but were never very successful due to lack of oxygen transmission. A number of years ago, a new generation hybrid lens was released. This design definitely has a big role to play once RGP lenses fail. Hybrid lenses are also great options when any form of dynamic sport is involved. They just do not fall out. Read more about hybrid lenses here.
Moving on from there we also have scleral contact lenses. These designs have made a resurgence among contact lens experts, as they are able to vault the very fragile advanced keratoconic cornea. Even very advanced keratoconus can be fitted successfully. Learn more about scleral lenses here.