Evaluation of the Robustness of Current Quantitative Criteria for Keratoconus Progression and Corneal Cross-linking

Abstract

The criteria used to define keratoconus progression were satisfactory when compared to inter-session reliability of corneal parameters. Because higher variability was noted at apex, its curvature repeatability cut-off may be raised to 1.25 D for identifying progressive keratoconus. [J Refract Surg. 2016;32(7):465-472.].

Repeated Same-Day Versus Single Tomography Measurements of Keratoconic Eyes for Analysis of Disease Progression

“…This finding is comparable with the results of Prakash et al 21 for a CV of 7.2%. Prakash et al 21 also found a low CV of 0.4% for SimKave, which was confirmed in our study.…”

“…Hence, criteria for progression with an increase as low as 0.5 D over a certain period seem to be insufficient for the purpose of detecting “true” progression of the disease and not merely a numerical increase in measurement results. A recently published study by Prakash et al 21 came to the same conclusion. The authors recommended the curvature repeatability cutoff to be set as high as 1.25 D. In this context, keep in mind that that criteria for progression in clinical trials often include an increase in different K-readings by only 0.5 to 1.0 D. 21 Interestingly, in our study, SimKast had one of the highest CVs at 11.4%.…”

“…The authors recommended the curvature repeatability cutoff to be set as high as 1.25 D. In this context, keep in mind that that criteria for progression in clinical trials often include an increase in different K-readings by only 0.5 to 1.0 D. 21 Interestingly, in our study, SimKast had one of the highest CVs at 11.4%. This finding is comparable with the results of Prakash et al 21 for a CV of 7.2%. Prakash et al 21 also found a low CV of 0.4% for SimKave, which was confirmed in our study.…”

“…We also chose this cutoff because it has been used in previous trials, although several authors advocate for the use of even higher thresholds. 20 , 21 …”

Evaluation of keratoconus progression

“…In the available literature,17 whole numbers rather than decimals are currently used, for example, for Kmax, a cut-off of 1 dpt and for Pachymin a cut-off of −10 µm. The KPI takes curvature as well as corneal thickness into consideration.…”