Nomogram M addresses epi-off cross-linking of thin corneas

PARIS — Thin corneas can safely and effectively undergo epi-off corneal cross-linking using a new nomogram that customizes cross-linking parameters and depth of the demarcation line.

Nomogram M was created by Cosimo Mazzotta, MD, PhD, cross-linking pioneer, who received the Joseph Colin Keratoconus Award, attributed each year to the best papers published in the Journal of Keratoconus and Ectatic Disease. The award was created as a memorial tribute to Joseph Colin, MD, world-renowned keratoconus expert and OSN Europe Editorial Board member, who passed away in 2013. The award is given each year at the European Society of Cataract and Refractive Surgeons meeting.

The nomogram M allows epithelium-off accelerated cross-linking to be customized to corneas of a wide range of thickness values, including very thin corneas.

“Based on pachymetry and maintaining the standard Dresden protocol fluence of 5.4 J/cm², UV light power and irradiation time are varied according to corneal thickness values and to where we predict the demarcation line should be to make the procedure safe for the endothelium but effective as a treatment. At least two-thirds of the initial thickness are cross-linked,” Mazzotta said in an interview with

Thin corneas have been a limitation and a major challenge for cross-linking. Several attempts were made, ranging from the use of hypo-osmolar riboflavin to mechanical shielding with a contact lens to Mazzotta’s own “epithelial islands” technique. However, none of these techniques was ever validated as a standardized, reproducible method.

“The nomogram M was an attempt to standardize the treatment of thin corneas, based on OCT and confocal microscopy studies,” Mazzotta said. “Corneas between 250 µ and 400 µ, epithelium included, can safely be treated, using accelerated cross-linking with pulsed or continuous light.” – by Michela Cimberle

Reference: Mazzotta C, et al. Pachymetry-based accelerated cross-linking: the ‘M nomogram’ for standardized treatment of all-thickness progressive ectatic corneas. Joseph Colin Keratoconus Award. Presented at: European Society of Cataract and Refractive Surgeons meeting; Sept. 13-18, 2019; Paris.