Corneal Collagen Cross-linking with Riboflavin and Ultraviolet A Irradiation for Keratoconus: Long-term Results

Abstract

To evaluate the long-term results of corneal collagen cross-linking (CXL) in patients with progressive keratoconus. Prospective case series. This study was conducted on 40 eyes of 32 patients with progressive keratoconus between 2006 and 2012. Patients underwent CXL no later than 1 month after baseline examinations. For CXL, ultraviolet irradiation was applied for 30 minutes, during which riboflavin instillation was repeated every 3 minutes. Patients were tested for best-corrected visual acuity (BCVA), uncorrected visual acuity (UCVA), manifest refraction spherical equivalent (MRSE), and Scheimpflug imaging from which we extracted maximum keratometry reading (max-K), average of minimum and maximum keratometry readings (mean-K), central corneal thickness (CCT), and anterior and posterior elevation at the apex at baseline, at 1, 3, 6 months after CXL, and 1, 2, 4, and 5 years later. We studied results at 5 years after CXL as well as the trend of changes over the 5-year period. Mean UCVA was 0.67 ± 0.52 logarithm of the minimum angle of resolution (logMAR) at baseline and 0.65 ± 0.51 logMAR at 5 years after the procedure. For mean BCVA, these values were 0.31 ± 0.28 and 0.19 ± 0.20 logMAR, respectively (P = 0.016). The mean MRSE changed from -3.18±2.23 diopters (D) to -2.77 ± 2.18 D, and mean refractive cylinder error changed from -3.14 ± 2.22 to -2.49 ± 1.71 D (P = 0.089). Mean max-K and mean-K decreased by 0.16 ± 2.20 and 0.10 ± 1.69 D, respectively. The CCT increased from 483.87 ± 29.07 to 485.95 ± 28.43 μm. Mean anterior elevation at the apex changed from 13.9 2 ± 8.28 to 11.45 ± 8.18 μm (P = 0.030) and posterior elevation at this point changed from 29.54 ± 18.39 to 26.34 ± 19.59 μm. The mean-K, max-K, UCVA, and astigmatism showed no change over time during these 5 years. After the first year, BCVA, MRSE, and CCT showed no change and stabilized, whereas elevation readings continued to decrease up to 5 years after CXL. Based on our 5-year results, treatment of progressive keratoconus with CXL can stop disease progression, without raising any concern for safety, and can eliminate the need for keratoplasty. The authors have no proprietary or commercial interest in any of the materials discussed in this article.