Keratometry Changes Between Year Seven and Twelve After Corneal Crosslinking in Patients with Keratoconus

<b>Background/Objectives</b>: To evaluate the timing and extent to which late keratometric changes can occur between year 7 and 12 after corneal collagen crosslinking (CXL) in patients with keratoconus. <b>Methods</b>: A subgroup of a retrospective cohort study of all consecutive patients who underwent CXL at our cornea center between 2007 and 2011 was analyzed. The inclusion criteria consisted of CXL according to the Dresden protocol and a full set of keratometry parameters collected by Scheimpflug tomography preoperatively and at year 7, 9 and 12 after CXL. <b>Results</b>: A total of 46 eyes of 35 patients were included. The most relevant keratometric parameters (Kmax, TCT, K1, K2 and anterior astigmatism) decreased statistically significantly at year 7 after CXL, while there was no relevant difference for posterior astigmatism and the flat axes of anterior and posterior astigmatism. All keratometric parameters (except for K2) remained stable between year 7 and 12 without statistically significant change, according to mixed effect model regression analysis. BCVA improved statistically significant between the baseline and year 7 and remained stable until year 12. Suspected disease progression was noted in two patients (4.3%) between year 7, 9 and 12 post-CXL. <b>Conclusions</b>: Keratometric and functional results improve significantly 7 years after CXL in comparison to preoperative values and show very effective stabilization without clinically relevant changes up to year 12. However, while the risk of disease progression decreases remarkably after 7 years, in rare cases, suspected progression can occur even up to year 12. Therefore, regular control visits with keratometry measurements are advisable at least every 2 to 3 years in the late postoperative course.