This article was originally published in a sponsored newsletter.

Corneal collagen cross-linking incorporates the use of ultra-violet (UV) light and riboflavin (vitamin B2) drops. The absorption of UVA by riboflavin creates radical riboflavin and singlet oxygen to form cross-links.¹ Corneal cross-linking forms new corneal collagen cross-links, which results in a shortening and thickening of the collagen fibrils and creates stiffening of the cornea.² For many, corneal cross-linking has been revolutionary in the treatment of keratoconus to effectively halt ectatic progression.
 
A cross-sectional cohort study described the visual and topographic outcomes 10 years following corneal cross-linking in individuals with progressive keratoconus and corneal ectasia after refractive surgery.³ The single-center prospective, randomized, clinical trial was conducted to evaluate patients who were in the U.S. pivotal trials, which led to the U.S. Food and Drug Administration approval of corneal cross-linking.³ Patients were enrolled for an examination 10 years after the pivotal trials. The study evaluated 19 eyes of 13 patients treated with standard cross-linking.
 
Uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), logMAR, maximum keratometry, and thinnest pachymetry were assessed. Progression was determined with the Belin ABCD progression display of the anterior curvature, posterior curvature, and corneal thickness of each eye.

Ten years after cross-linking, mean maximum keratometry values were 58.3D ± 10.1Dfrom 58.2D ± 12.0D and thinnest pachymetry values were 442.3μm ± 54.4μm from 440.6μm ± 51.6μm. Using logMAR lines (LL), UCVA changed from 0.79LL ± 0.42LL to 0.86LL ± 0.46LL, and BSCVA changed from 0.38LL ± 0.26LL to 0.33LL ± 0.34LL 10 years following cross-linking.
 
Corneal ectasia continued to be topographically stable 10 years after standard cross-linking in 68.5% of the entire cohort. In eyes that had keratoconus, 81.8% of eyes were topographically stable. In eyes that had corneal ectasia, 50% of eyes maintained topography stability. In this study 10 years after cross-linking, eyes that had keratoconus were more stable than those that had corneal ectasia.
 
All patients after cross-linking treatment should be advised about the importance for continuous follow-up examinations after treatment. Specifically, individuals that have corneal ectasia after laser refractive surgery should be instructed on possible progression after corneal cross-linking and the possibility for future cross-linking retreatment.
 
A limitation of the study is the small sample size. Of those enrolled in the original clinical trial, a small percentage of the patients returned since nearly half of them had other corneal procedures and were ineligible to be evaluated for progression or stability.

REFERENCES

1. Kamaev P, Friedman MD, Sherr E, Muller D. Photochemical kinetics of corneal cross-linking with riboflavin. Invest Ophthalmol Vis Sci. 2012 Apr 30;53:2360-2367.

2. Beshtawi IM, O’Donnell C, Radhakrishnan H. Biomechanical properties of corneal tissue after ultraviolet-A-riboflavin crosslinking. J Cataract Refract Surg. 2013 Mar;39:451-462.

3. Greenstein SA, Yu AS, Gelles JD, Huang S, Hersh PS. Long-Term Outcomes After Corneal Cross-linking for Progressive Keratoconus and Corneal Ectasia: A 10-Year Follow-Up of the Pivotal Study.

Melissa Barnett, OD, FAAO, FSLS, is the Director of Optometry at the University of California, Davis in Davis, specializing in anterior segment disease and specialty contact lenses. She is the past president of the Scleral Lens Education Society. She is an advisor to and/or has received honoraria or travel expenses from AccuLens, Alcon, Allergan, Bausch + Lomb, Bruder, Contamac, CooperVision, Johnson & Johnson Vision, Ocusoft, ScienceBased Health, Shire, Tarsus, and Visus Therapeutics.