Repeatability of corneal deformation response parameters by dynamic ultra–high-speed Scheimpflug imaging before and after corneal crosslinking

Purpose: To evaluate the repeatability of deformation corneal response (DCR) parameters before and after corneal crosslinking (CXL) compared with their untreated fellow eyes (uFEs). Setting: University Hospital Carl Gustav Carus, Dresden, Germany; IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy. Design: Multicenter, interventional reliability analysis. Methods: 53 eyes of 53 patients with keratoconus who received CXL treatment after the disease progression (CXL group) were included. Patients were measured 3 times using a dynamic Scheimpflug analyzer to determine repeatability before and 1 month after CXL treatment. The uFEs were measured in the same way (uFE group). Reliability of DCR parameters was assessed by a coefficient of repeatability, coefficient of variation, and intraclass correlation coefficient (ICC). Results: The repeatability of DCR parameters did not change after CXL compared with the preoperative values for all investigated DCR parameters ( P > .05). In the uFE group, no statistically significant shift was observed regarding the repeatability ( P > .05). An ICC greater than 0.75 was achieved in both groups for almost all parameters. Concerning the biomechanical stiffening induced by CXL, integrated inverse radius and stress-strain index were found to be statistically significantly decreased and increased ( P < .001), respectively, both indicating stiffening. No changes were observed for the uFE group. Conclusions: The study demonstrated highly repeatable measurements of the dynamic Scheimpflug analyzer before and after CXL. The improvement of certain DCR parameters after CXL confirmed the capability of the device to detect the stiffening effect.