Table 7. Summary of endothelial cell density (ECD) outcomes from representative studies across protocols in progressive keratoconus.

A-CXL: accelerated corneal cross-linking; CXL: corneal collagen cross-linking; ECD: endothelial cell density (the number of endothelial cells per square millimeter in the cornea); TE-CXL: transepithelial corneal cross-linking

CXL Protocol	Mean Baseline ECD (Range)	Mean Follow-up ECD (Range)	Mean Change (Range)	Mean Follow-Up (Range)	Statistical Significance
Dresden [14-16,34-37,40,50,58,72,73,75,85,91]	2697.8 cells/mm2 (2690–2846)	2682 cells/mm2 (2672–2805)	-15.8 cells/mm2 (-33 to +3)	17.5 months (6–40)	No significant differences in ECD were observed within or between protocols (p > 0.05).
TE-CXL [14,37,40,42,45,50,51,58,61]	2663 cells/mm2 (2545–2750)	2651.6 cells/mm2 (2532–2738)	-13.2 cells/mm2 (-100 to -12)	21.1 months (12–40)	No significant differences in ECD were observed within or between protocols (p > 0.05).
A-CXL [16,62,72,73,75,80,85,91,93]	2772.3 cells/mm2 (2485–2854)	2742.9 cells/mm2 (2468–2821)	-29.4 cells/mm2 (-15 to -12)	11.5 months (6–24)	No significant differences in ECD were observed within or between protocols (p > 0.05).