The study was done to compare immediate sequential bilateral corneal cross-linking (CXL), wherein both eyes are treated on the same day, to delayed sequential bilateral CXL, where each eye is treated on different days for bilateral progressive keratoconus.

This was a retrospective case note review of all patients who underwent sequential CXL or delayed CXL for keratoconus at Royal Liverpool University Hospital, United Kingdom. Parameters assessed were the change in maximum keratometry and minimum central corneal thickness on corneal tomography scan, corrected distance visual acuity, and cost estimates of treatment.

A total of 38 patients (31 men and 7 women) with keratoconus with a mean age of 25.3 ± 7.0 years were included. Twenty patients received sequential CXL and 18 received delayed CXL treatment. In both the sequential CXL and delayed CXL groups, the treated eye(s) showed no evidence of progression after the corneal CXL treatment at last follow-up visit after 358 ± 158 days for sequential CXL and 451 ± 205 days for delayed CXL. There were no complications from the treatment in either group. In the delayed CXL group, the mean time interval between the two CXL procedures was 146 ± 129 days. Five of 18 patients (27%) showed progression of keratoconus in their second eye during the waiting time. Economical evaluation showed that four visits were saved for each sequential CXL treatment compared to delayed CXL.

The study concluded that the delayed CXL carries a risk of progression in the second eye and is associated with a higher economic burden.