Progression Analysis with ABCD Grading System following Corneal Collagen Cross-Linking in Keratoconus

INTRODUCTION: To evaluate the ABCD grading system used in follow-up of keratoconus progression after the corneal collagen cross-linking (CXL) treatment in different Kmax groups.
METHODS: This study included 57 eyes of 43 patients applied with CXL treatment for progressive keratoconus. All the patients were applied with the standard CXL protocol (Dresden). According to the changes in the Kmax value at the end of 12 months postoperatively (0–1D, 1–2D, >2D), the groups were separated as steepening and flattening. Scheimpflug progression parameters, such as ABCD keratoconus grading systems, were evaluated in six different groups. The Paired Samples t-test was used in the evaluation of parameters with normal distribution and the Wilcoxon test for parameters not showing normal distribution. A value of p<0.05 was accepted as statistically significant.
RESULTS: Mean age of patients was 18.37±3.86 years (11–28 years). According to the ABCD grading system, 0.19 significant regression was determined in grade A (p=0.014) and 0.24 in grade D (p<0.0001). 0.10 progression was seen in grade B (p=0.089), and 0.11 in grade C (p=0.011). In the mean Kmax value 0.25±0.42, D flattening was seen (p=0.137).
DISCUSSION AND CONCLUSION: The anterior corneal surface grade in ABCD system is correlated with Kmax in different groups. However, the posterior corneal surface parameter is not correlated with Kmax in 1-2 D steepening and >2D flattening groups. Although there is an increase in posterior elevation after CXL, despite excessive Kmax flattening, it would be inaccurate to consider this increase as an indicator of topographic progress.