In the ‘70s and ‘80s, contact lens management of keratoconus patients consisted almost exclusively of any one of several available small-diameter rigid lenses. Today, the toolbox includes sclerals, intralimbal GPs, custom soft lenses, and hybrids. Scleral lenses, in particular, appear popular, as a recent survey of eyecare practitioners fitting contact lenses showed that almost 51% of respondents fit, at minimum, 50% of their irregular cornea patients into scleral lenses (Bennett, 2017). We will review a preliminary approach to using today’s available tools for fitting keratoconus patients.
Age of Onset
For young (i.e., teenage onset) progressive keratoconus patients, we recommend initiating a discussion about corneal cross-linking as an option. Although the results have varied in terms of slowing progression and even reducing existing change, and (of course) there is the cost involved, this option has benefitted an increasing number of young patients since its recent approval by the U.S. Food and Drug Administration. It is evident that this procedure will continue to be refined and will improve in its effectiveness and success in the future (Hauswirth, 2017).
Degree of Progression
Mild For early keratoconus patients (defined here as average keratometry or Sim K values between 45D to 50D), several options are available. Custom soft and hybrid lenses can be successful for many of these patients, as can small-diameter lenses for keratoconus and intralimbal GP lenses (overall diameter in the 10.5mm to 11.5mm range). For GP wearers, we recommend either very mild central touch or minimal clearance with moderate edge clearance.
Moderate When the average K value is between 50D and 55D, sclerals are often our go-to lens, although hybrids and intralimbals can also be successful in these cases.
Severe When the average K value is greater than 55D, scleral lenses are the lens of choice for comfort, vision, and fit.
Size and Location of Cone
Central “Nipple” Cone According to the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) topography assessment group, almost 29% of keratoconus patients in the CLEK study had this type of cone (McMahon, 2008). With these patients, a small-diameter or intralimbal GP should center well and would be the best choice.
Oval Cone An intermediate-sized cone, present in more than 44% of patients in the aforementioned CLEK study, would benefit from any of the available options, notably intralimbal, hybrid, and scleral lenses.
Globoid Cone With most of the cornea impacted (and found in about 7% of CLEK patients), a scleral or hybrid lens would be indicated to provide optimum centration.
Marginal Cone About 6% of subjects in the same CLEK study had this form of cone, which is typically decentered inferiorly. A scleral lens would be recommended, although both intralimbals and hybrids can be successful. If it is a mild form of the disease, custom soft lenses can be used as well.
The GP Lens Institute (www.gpli.info ) offers webinars and a Scleral Lens FAQs Troubleshooting Guide. In addition, the Scleral Lens Education Society (www.sclerallens.org ) offers hands-on workshops and numerous other resources. Of course, the best resource is often your laboratory consultant. For a more comprehensive guide to lens selection and the surgical procedures, check out next month’s feature article by Dr. Jeffrey Sonsino and colleagues.
A step-wise approach can be successful to prescribe the most appropriate lens that provides optimal optical correction or physiological improvement while improving the quality of life for those individuals who have irregular corneas. CLS
For references, please visit www.clspectrum.com/references and click on document #266.