The Belin ABCD Progression Display can provide additional information to assist both surgeon/patient in determining the proper time to intervene in keratoconus.
Corneal collagen crosslinking (CXL) offers the opportunity to slow, stabilize, or even partially reverse what has been a chronically progressive disease in keratoconus. Though CXL has been available for more than a decade outside the United States, its usage within America is still, to some degree, in its infancy.
Adaption of this treatment modality has been hampered by both the expense and the lack of appropriate insurance coverage. When covered, however, many insurance carriers require documentation of further progression using the parameters from the FDA CXL trials.
The most commonly used progression parameter is an increase in Kmax of 1 D or more. Parameters used in FDA trials are just that, and are not meant to set or establish a standard of care, let alone used limit access to care.
An abnormal anterior surface with an elevated Kmax already implies some degree of visual compromise. A further increase in Kmax, as required by many carriers, is typically associated with a further reduction in visual function.
This is contrary to our normal practice of medicine. When we identify a patient with elevated serum cholesterol levels, we empirically start the patient on a statin. We do not wait until they have an occlusive event.
Yet, frequently, our current approach to keratoconus is to intervene only after the patient has already lost vision. This is secondary to both a late diagnosis and the mandate that anterior surface parameters, such as Kmax, must change before carriers will cover the cost of CXL. A few years ago, we introduced a new classification system (Table 1) on the OCULUS Pentacam, the Belin ABCD Keratoconus Staging, to replace the grossly outdated, but commonly used, Amsler-Krumeich Classification.
Michael W. Belin, MD
E: [email protected]
Dr. Belin is professor of ophthalmology and vision science, University of Arizona, Tucson. He serves as a consultant to Avedro, CXLO, and OCULUS Optikgeräte GmbH
1. Belin MW, Duncan J. Keratoconus: The ABCD Grading System. Klin Monbl Augenheilkd. 2016;233:701-707
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3. Belin MW, Meyer JJ, Duncan JK, Gelman R, Borgstrom M, Ambrosio R. Assessing progression of keratoconus and crosslinking efficacy: The Belin ABCD Progression Display. Int J Kerat Ect Cor Dis. 2017;6:1-10.
4. Belin NW, Lim L, Rajpal RK et. al. Corneal Cross-Linking: Current USA Status – Corneal Society Guidance Document. Cornea. 2018;37:1218–1225.