Conventional vs. pulsed-light accelerated corneal collagen cross-linking for the treatment of progressive keratoconus: 12-month results from a prospective study

The aim of the present study was to compare the clinical outcomes of conventional corneal collagen cross-linking (CXL) and pulsed-light accelerated CXL (pl-ACXL) in the eyes of patients with progressive keratoconus. A total of 72 eyes with progressive keratoconus in 58 patients were equally divided into the CXL and pl-ACXL treatment groups. The CXL treatment was performed using the UVX 1000 system with 0.1% riboflavin solution in 20% dextran presoak for 30 min, and 3 mW/cm2 ultraviolet A (UVA) light for 30 min. The pl-ACXL group was treated with the KXL system using 0.1% riboflavin with HPMC presoak for 10 min, followed by 8 min (1 sec on/1 sec off) of 30 mW/cm2 UVA light. Patients were evaluated according to the uncorrected distance visual acuity (UDVA), corrected DVA (CDVA), refraction, maximum keratometry (Kmax), endothelial cell density (ECD), anterior segment optical coherence tomography and in vivo confocal microscopy. The follow-up period was 12 months. Transient haze was observed in 17 eyes (47.22%) in the CXL group and 8 eyes (22.22%) in the pl-ACXL group at 1 month postoperatively. There were no significant postoperative differences in the astigmatism, manifest refraction spherical equivalent, ECD or thinnest corneal thickness. By contrast, UDVA, CDVA and Kmax presented significant improvement at 12 months postoperatively in the two groups. The demarcation line depth was 284.94±33.29 µm in the CXL group, which was significantly deeper in comparison with that in the pl-ACXL group (201.64±27.72 µm; P<0.01) at 1 month postoperatively. In vivo confocal microscopy revealed keratocyte apoptosis and stromal edema at 1 month postoperatively, which gradually recovered towards the normal status after 12 months in the two groups. There were no apparent changes in the posterior stroma and endothelium in either group. The results of the present study revealed that CXL and pl-ACXL were safe and effective procedures in stabilizing the progression of keratoconus. The CXL technique offers more effective visual and topographic outcomes compared with pl-ACXL, while pl-ACXL ensures shorter treatment time and reduced microstructural damage.