editor's perspective

Contact Lenses For Keratoconus

Narrowing the Information Gap

BY JOSEPH T. BARR, OD, MS, EDITOR
AUGUST 1998

I spend many hours each week working with keratoconus as a researcher and a clinician, and I'm still amazed by the vast lack of a consensus on how to fit keratoconus patients with contact lenses. We're learning more, but it's a slow process. At least three-fourths of keratoconus patients (in developed countries) use contact lenses for best vision. About 97 percent of them use RGPs. We probably underutilize toric soft contact lenses in the early stages of the condition, and we probably too often avoid piggyback fitting in the moderate to later stages of keratoconus. We certainly don't know how to best fit the RGP lenses.

Oh sure, there are some of you out there who are 100 percent certain about what's best. But I'm always concerned when people are 100 percent certain -- they often have the answer without the data to support it. A few practitioners are sure that a flat fit is ideal to maintain best corneal shape and integrity. Another group is equally certain that only steep lenses should be fitted to prevent scarring induced by flat fitting lens abrasions. Practitioners who have more experience than I tell me that a scleral lens is the worst thing in the world for keratoconus, yet numerous reports of new high Dk RGP scleral lenses (as well as old-fashioned PMMA scleral lenses) used for keratoconus are very positive. I've seen many patients who have worn flat-fitting lenses all their lens-wearing years and have had no corneal scarring. Of course, we know that scarring can occur in the absence of contact lens wear. Most practitioners report better vision with flat fitting lenses in keratoconus than with steep fitting lenses, yet the well-researched data do not make this a firm conclusion.

New contact lens manufacturing and inspection methods allow more complex aspheric geometries to be fabricated in RGP lenses with good repeatability. Some of these designs have well-conceived fitting nomograms. Off-center optic zones are yet another design option. However, the evidence that these designs truly help the keratoconus patient is anecdotal.

So how do we care for keratoconus patients who desperately need contact lenses? Careful examination, careful fitting for best vision, comfort and minimal tissue insult (no we're not sure exactly which design is best), control of wearing time and clean lenses are all essential. As we learn more about the histopathology of the condition, perhaps a medication to help minimize the changes in the cornea will be developed, but this is likely years away. Until then, we'll try to provide you with the best information we can on all the fitting alternatives.