Keratoconus, a degenerative eye disease, generally causes vision problems that cannot be adequately corrected with eyeglasses.

But specially designed contact lenses often provide excellent visual acuity for people suffering from mild or even moderate stages of keratoconus.

In the January 2010 issue of Optometric Management, Gregory W. Denaeyer, OD, reviews four contact lens strategies for correcting vision problems caused by keratoconus:

Specialty soft contact lenses. This option often works well for individuals with mild keratoconus. Several contact lens companies produce specially designed soft contacts to fit the steep curvature of mildly keratoconic eyes, and these lenses also can correct significant amounts of keratoconus-induced astigmatism, according to Dr. Denaeyer.

Bi-aspheric gas permeable contacts. Gas permeable contact lenses that are aspheric on both surfaces (bi-aspheric) offer two advantages for keratoconus patients. The aspheric back surface helps the lenses stay centered for a more comfortable fit, and the aspheric front surface helps reduce higher-order aberrations for sharper vision, Dr. Denaeyer says.

“Piggybacking” contact lenses. This strategy involve fitting a gas permeable (GP) contact lens over the top of a soft lens. The GP lens can be specially designed to provide optimal vision for the keratoconic eye, and the underlying soft lens provides a cushioning effect for greater comfort. The soft lens also may help improve the fit of the GP lens and protect the cornea from friction caused by the GP lens that could otherwise lead to corneal scarring.

Scleral contact lenses. Specialty gas permeable lenses called scleral contact lenses are much larger in diameter than regular GP lenses so they can vault over the entire cornea and rest on the white of the eye (sclera). The large size of scleral lenses reduces pressure on the cornea and enables the lenses to stay centered, even on highly irregular keratoconic eyes.

Eye doctors who can offer their keratoconus patients all four of these contact lens strategies will help improve the fit and comfort of their contacts and help provide optimum vision, Dr. Denaeyer says.

[Ed. note: Another strategy not discussed by Dr. Denaeyer is the use of hybrid contact lenses. Essentially, the center of a hybrid contact is a gas permeable lens and the peripheral portion is a soft lens. Special hybrid lens designs are available specifically for keratoconus.]

SOURCE:  Four strategies for keratoconus. Optometric Management. January 2010.

Scleral contact lenses provide acceptable visual acuity and comfort in patients with keratoconus, according to researchers evaluating the effect of these extra-large gas permeable (GP) lenses on people with the corneal condition.

In a report published in this month’s issue of Eye & Contact Lens, researchers Muriel M. Schornack, OD, and Sanjay Patel, MD,  described the results of a study of 32 patients with keratoconus who were evaluated for scleral contact lens wear.

Of these, 12 patients (37.5 percent) decided not to be fitted with scleral lenses after an initial contact lens exam and consultation.

The remaining 20 patients (32 eyes) underwent the fitting process with Jupiter scleral contact lenses (Medlens Innovations, Front Royal, Va., and Essilor Contact Lenses, Inc., Dallas, Texas).

Mean best-corrected visual acuity (BCVA) of the keratoconic eyes prior to being fitted with the scleral lenses was 20/76, as tested on a standard eye chart. After being successfully fitted with the lenses, mean BCVA improved to 20/30.

One patient (two eyes) abandoned the fitting process because he needed cataract surgery. The remaining patients (95 percent) continued to wear the scleral lenses successfully over a follow-up period ranging from 3 to 32 months.

Scleral contact lenses differ from conventional gas permeable contacts in their size and design. Scleral lenses have a much larger diameter than regular GP lenses so they can vault over the entire clear front surface of the eye (cornea) to correct vision problems caused by severe corneal irregularities.