To determine 18-month changes in mesopic contrast sensitivity (CS) and higher order aberrations (HOA) after accelerated collagen cross linking (CXL) in keratoconic patients.

In this before-after interventional case series, 70 eyes of 623 keratoconic patients underwent accelerated CXL (18 mW/cm2, 5 min). Patients were examined with OPD Scan III and CVS-1000 grating charts under mesopic conditions at baseline, and at 6 and 18 months.

At 18 months postoperatively, compared to baseline, mesopic CS at spatial frequencies of 3, 6, 12, and 18 cycle/deg reduced by 0.05±0.27, 0.04±0.30, 0.04±0.21, and 0.02±0.18, respectively, which were statistically insignificant (all P>0.05). There was a reduction of 0.12±0.44µm in ocular HOA; 0.19±0.91µm in coma, 0.07±0.34µm in trefoil, and 0.02±0.15µm in spherical aberration (SA) (all P>0.05). Decreases in corneal HOA, including coma (0.61±3.60), SA (1.70±5.72) and trefoil (.08±4.14) were not statistically significant (all P>0.05). Coma had the largest share of corneal HOAs before and 18 months after the procedure, and the most reduction was observed in corneal SA.

At 18 months after accelerated CXL, despite reduced keratometry and corneal flattening, mesopic CS as well as ocular and corneal HOAs remained unchanged, and the procedure was not associated with reduced quality of vision.