Background: Intrastromal corneal ring segments (ICRS) attain regularization of corneal surface in keratoconus (KC), while collagen cross-linking (CXL) halts or slows its progression. The long-arc 320° rings combined with CXL may have a dual-benefit synergistic effect of surface regularity and progression halt.
Methods: This was a prospective case series study including eyes with progressive KC. Femto-assisted 320° ICRS implantation and epi-off CXL 8 weeks later were carried out in all cases. Uncorrected (UCVA) and corrected distance visual acuity (CDVA) were assessed using Snellen's chart, while corneal tomography was evaluated using Scheimpflug imaging. Follow-up was carried out 3, 6, and 12 months after the CXL.
Results: Thirty-two eyes of 32 patients with progressive KC were included, 18 males and 14 females, and the mean age was 23.1 years. According to the Amsler-Krumeich classification, four eyes had stage 1 KC, 20 had stage 2 KC, and eight had stage 3 KC, and UCVA and CDVA improved from 0.1 ± 0.15 and 0.2 ± 0.19 to 0.4 ± 0.2 (P> 0.01) and 0.5 ± 0.2 (P> 0.01) respectively at 12 months. Manifest refraction spherical equivalent was reduced from - 5.6 ± 2.3 to - 1.1 ± 1.3 D at 12 months after the procedure (P> 0.01). In addition, maximum keratometry was significantly reduced from 54.8 to 49.3 diopters (P> 0.01), while the asphericity index (Q value) has changed from - 1.4 to - 0.25 (P> 0.01) after 12 months. No significant differences were detected between central (n = 12) and eccentric (n = 20) KC in all outcomes.
Conclusion: The 320° ICRS-CXL protocol has improved the visual and the tomographic outcomes at 1 year in our patients with progressive KC. No differences were detected between central and eccentric cases. Further larger studies could ensure the safety profile of the combined protocol.
Keywords: Corneal rings; Cross-linking and central/eccentric cones; Keratoconus.