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

Abstract

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.

The meaning of the demarcation line after riboflavin-UVA corneal collagen crosslinking

“…Jiang et al 70 documented that the DL depth in the pulsed light 30mW/cm 2 A-CXL group was 201 ± 27 µm at 1 month postoperatively confirming Mazzotta's first observation 67 as showed in Figure 4 c -d. The study revealed keratocyte apoptosis and stromal edema at 1 month postoperatively, which gradually recovered towards the normal status with no changes in the posterior stroma and endothelium. Pulsed light A-CXL 71 was safe and effective procedure in stabilizing the progression of keratoconus and by comparing the S-CXL, where the DL depth was 284.94±33.29 µm, authors obtained more effective visual and topographic outcomes than with pulsed light 30mW/cm A-CXL group.…”

“…70,71 The pulsed light A-CXL ensured a shorter treatment time, increased the average penetration of the DL from 150 µm of the continuous light to 200 µm and reduced postoperative microstructural damage thus limiting stromal wound healing reactivity. 67,70,71 Substantially, the kinetic models after S-CXL and A-CXL protocols confirmed that there is a faster oxygen depletion and a slow oxygen replenishment shifting the CXL photodynamic reaction predominantly in the type I. It happens also in the standard protocol with continuous light UV-A exposure because of the fast oxygen consumption (10-15 sec) during the UV-ON phase.…”

Prospective two‐year study of clinical outcomes following epithelium‐off pulsed versus continuous accelerated corneal crosslinking for keratoconus

“…We found no significant improvement in UDVA and CDVA at 1 year following c‐ACXL and p‐ACXL. This is in keeping with a previous prospective study reporting no improvement in UDVA and CDVA at 1 year following p‐ACXL . In our series, after 24 months of follow‐up, a statistically significant improvement was noted in CDVA in both groups.…”

“…This is in keeping with a previous prospective study reporting no improvement in UDVA and CDVA at 1 year following p-ACXL. 18 In our series, after 24 months of follow-up, a statistically significant improvement was noted in CDVA in both groups. There was no significant difference detected in mean visual acuity gain between the two groups.…”

Corneal Crosslinking in Progressive Keratoconus: Comparison of Dextran-Based and Hydroxypropyl Methylcellulose-Based Riboflavin Solutions Differences in demarcation line depth and 1 yaear outcomes

“…The transition of crosslinked to non-crosslinked tissue is detected as a demarcation hyperreflective line within the corneal stroma ( fig.4), possibly representing the effectiveness of the CXL treatment. Studies have shown that the demarcation line is biomicroscopically detectable in slit lamp examination as early as 2 weeks after treatment and it can be equally detected by confocal microscopy and anterior segment optical coherence tomography (AS-OCT) up to a depth of aproximately 300µm [15][16][17][18].…”