Eight-year results of laser in-situ keratomileusis with or without combined accelerated cross-linking in highly myopic eyes

Purpose: To analyze the 8-year results of femtosecond laser-assisted-in-situ-keratomileusis (LASIK) combined with simultaneous accelerated corneal cross-linking (LASIK-Xtra) compared to conventional LASIK (convLASIK). Setting: Department of Ophthalmology, Goethe-University, Frankfurt, Germany. Design: A follow-up analysis of a prospective, randomized fellow eye-controlled clinical trial. Methods: Patients who received randomized treatment with the LASIK-Xtra (30mW/cm 2 , 90sec with continuous UVA) in one and convLASIK in the fellow eye were subjected preoperatively, 1 (pos1y) and 8 years postoperatively (pos8y) to subjective refraction, uncorrected (UDVA) and distance-corrected visual acuity (DCVA), endothelial cell count (ECC), biomechanical evaluation, and tomographic examination. Results: Twenty-six eyes (-7.07±1.86 diopter [D]) from 13 patients (mean age 30.7±10.4 years) were included. UDVA and DCVA were insignificant different at pos1y and pos8y between convLASIK and LASIK-Xtra (each p>0.28). Safety index at pos8y was 1.09 for convLASIK and 1.15 for LASIK-Xtra (p=0.799), and the efficacy index 0.91 and 0.94 (p=0.875), respectively. Significant myopic shift in spherical equivalent between pos1y (-0.30±0.40D) and pos8y (-0.80±0.86D) was found in the convLASIK group (p=0.018), compared the LASIK-Xtra group (-0.25±0.49D and -0.40±0.86D; p=0.261), respectively. However, these refractive changes cannot be fully attributed to corneal alterations alone and may also reflect other factors. Insignificant differences in mean keratometry, corneal thickness, and ECC were found at pos8y (p>0.05). Stress-strain index was the only biomechanical parameter that was significantly higher in the LASIK-Xtra group at pos8y (p=0.034). Conclusion: After 8 years, no substantial disparities in efficacy and safety indices were observed between the two groups. There were no substantial differences in most of the evaluated postoperative corneal biomechanical parameters between the two groups. However, these findings need to be validated by further studies with larger sample sizes.