A Higher-energy Accelerated Corneal Collagen Cross-linking Method for Keratoconus: A Retrospective, Observational Cohort Study

Abstract

Introduction: Primary keratoconus is a non-inflammatory corneal ectasia disease with an unknown cause. Nowadays, the most widely used treatment method is corneal collagen crosslinking based on the Dresden protocol. Due to the long surgery time, we have been searching for a new method which cost less time in surgery. Methods: A retrospective, observational cohort study was used. A total of 31 participants (59 eyes) with primary keratoconus were collected. Twelve of them (24 eyes) used the standard Dresden protocol, and the remaining 19 (35 eyes) used a higher-energy accelerated corneal collagen cross-linking method. Application of riboflavin solution to the de-epithelialized cornea for 10 min, then the cornea is UVA irradiated (wavelength, 365 nm and power, 30 mW/cm²) for another 3.55 min, and the total irradiation energy is 6.4J/cm². Participants were followed up for 12 months after surgery and underwent complete examinations at 3, 6, and 12 months in predetermined windows of time. The examinations items include routine ophthalmological examination, uncorrected vision acuity (UCVA), best corrected visual acuity (BCVA), refraction, corneal curvature, the elevation of the thinnest point on front surface and back surface (F Ele Th, B Ele Th), the thickness of the thinnest point of the cornea (CT), and the density of the corneal endothelial cells (ECD). The independent sample t-test method was used to compare the changes of the parameters of the standard Dresden protocol and the higher-energy accelerated corneal collagen cross-linking. Results: In the A-CXL treatment group, the maximum keratometry value decreased by 1.48D from baseline, UCVA improved by an average of 0.07 logarithm of the minimum angle of resolution (logMAR) units, BCVA improved by an average of 0.15 logarithm of the minimum angle of resolution (logMAR) units. All of those are similar to standard Dresden protocol group. There were no significant changes in endothelial cell count and thickness of cornea 1 year after treatment. Conclusions: In this study, we found that accelerated corneal collagen cross-linking under 6.4J energy has a similar surgical effect as corneal collagen cross-linking under the Dresden protocol, and did not cause more adverse events.