To study one-year changes in uncorrected contrast sensitivity (CS) and corrected CS under scotopic conditions after accelerated cross linking (ACXL) compared to unoperated cases.

In this non-randomized clinical trial, 60 eyes (30 in each group) were enrolled. CS and glare were assessed under scotopic conditions using the Metrovision platform at baseline and at 6 and 12 months after the procedure. Patients were seated in the room for 10-15 minutes to adjust to lighting conditions.

Mean age of the participants was 24.32±5.17 years and 30.93±7.43 years in the ACXL and control groups, respectively (P<0.001). After adjusting for age, 1-year changes in uncorrected and corrected CS and glare were similar in the two groups (all P>0.05). Regression analyses indicated that corrected CS at low (0.5-2.2) spatial frequencies (SF) was not affected by ACXL or baseline CS (all P>0.05), but changes in corrected CS at 3.4 correlated with its preoperative values and was higher in cases with worse baseline CS. Corrected CS7.1 and CS15 related to both surgery and their corresponding baseline values; at both SFs, surgery caused decreased CS in those with better baseline CS and improved it in those with lower CS (all p<0.050). At one year, uncorrected CS was affected by baseline CS at all SFs (all P<0.001) and declined in those with better pre op and vice versa.

ACXL causes a reduction in scotopic corrected CS in SFs higher than 7 in cases with better baseline CS and vice versa. Changes in uncorrected CS are only influenced by preoperative CS; those with better pre CS have worse outcomes and vice versa.