Q: I noticed that there are several new soft lens options for thinning disorders like keratoconus. Are practitioners using these as first-line options or last-ditch efforts when rigid gas-permeable lenses or hybrids fail before grafting? How do the designs differ?
A: While there are a couple of new soft lens options for managing keratoconus and other irregular corneal astigmatism, the idea itself is not a new one, says Mark André, a contact lens specialist and associate professor of optometry at Pacific University, in Forest Grove, Ore. He has been using soft lenses to manage irregular astigmatism for more than three decades—starting with the Flexlens for Keratoconus (Walman Optical) in the late 1970s. “With the advent of more sophisticated manufacturing techniques and higher Dk materials, there has not been a better time to incorporate custom soft lenses for keratoconus into your practice,” Mr. André says.
While rigid corneal contact lenses have long been the go-to treatment for keratoconus, many patients are looking for a more comfortable lens that can be worn all day. New soft lens designs have made it possible to address the complex optical issues that keratoconus creates, while also providing more comfortable wear for many patients.1
The latest soft lenses for keratoconus on the market are NovaKone (Alden Optical) and KeraSoft IC (Bausch + Lomb). The biggest difference between the two lenses is the material—NovaKone is comprised of Benz G4X 54% water hydrogel material with a Dk value of 21, and KeraSoft IC is a lathe-cut silicone hydrogel material that is 74% water with a Dk value of 60. The NovaKone can be ordered in five different thicknesses in order to mask varying degrees of corneal distortion. Mr. André has found great success with both lens designs and recommends having both fitting sets if you have a large specialty contact lens practice.
|Patient wearing a soft custom lens for keratoconus. Photo: Patrick Caroline, C.O.T.
“Historically, custom soft lenses that mask irregular corneal astigmatism have met resistance from practitioners concerned with their increased lens thickness,” he says. “I rarely observe hypoxia-related complications with these specialty lenses, and the best explanation that I have is that they move up to 1mm with a blink. The increased tear exchange under the lens must make up for the relative decrease in oxygen transmissibility.”
He always considers soft lenses as one of his contact lens options for keratoconus before resorting to surgical intervention. “Generally, I will consider the rigid lens designs first, but if the patient has exhausted the rigid lens options or dislikes the comfort of rigid lenses, I would not hesitate to recommend a custom soft lens,” he says. “The visual outcomes we achieve with these lenses are often equal to, and in some cases better than, the results we get with rigid lenses.”
The patient’s corneal topography plays an important role in how successful the soft lens approach will be. Due to corneal asymmetry, patients with large-diameter sagging may be poor candidates because the steepening of the inferior cornea can cause the lens to lift inferiorly.1 However, corneas with nipple- and globus-type cones, with relatively concentric 360° peripheral topography, seem to respond well to soft lenses.1
“Take advantage of the manufacturer’s consultants to help you through the learning curve,” Mr. André says. “Once you build your confidence with fitting these lenses, you will wonder how you managed your challenging contact lens patients without them.”
1. Caroline P, Andre M, Kinsohita B, Choo J. Etiology, diagnosis, and management of keratoconus: new thoughts and new understandings. Pacific University College of Optometry. Available at:
www.pacificu.edu/optometry/ce/courses/15167/etiologypg4.cfm (accessed May 30, 2012).