Posterior corneal elevation changes and characteristic analysis 1 year after corneal collagen cross-linking for keratoconus

Purpose To investigate the changes in posterior corneal elevations (PCEs) in the circular areas and local points after corneal collagen cross-linking (CXL) for the treatment of keratoconus. Methods Method 1 divided the cornea into 0–2, 2–4, 4–6, and 6–8 mm regions centering on the apex. Method 2 obtained other 34 PCE values of local point that were identified on the nasal, supra-nasal, sub-nasal, superior, inferior, temporal, supra-temporal, and sub-temporal sides of the circle with diameters of 2, 4, 6, and 8 mm, and the apex and thinnest point. Results Method 1 showed a forward displacement of PCE at 1 month after CXL and then a backward displacement at 3 months. In Method 2, the points on the temporal side of 2 mm and 4 mm showed the same trend. The backward displacements of PCE on the temporal side of 2 mm at 6 months and on the temporal side of 4 mm at 12 months after CXL were both statistically different than those at 1 month after CXL ( P < 0.05). No significant forward displacement of PCE was found in all local points in different quadrants at 1 year after CXL. Conclusion The PCEs in circular areas and characteristic points of different diameters in keratoconic eyes after CXL change with time. Local point assessment of the PCE is more clinically significant. In points selected in different quadrants of the cornea, the change in temporal points was more significant after CXL.