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Updated: Jul 26, 2025
Scleral Cross-linking Using Riboflavin and Ultraviolet-A Radiation for Prevention of Axial Myopia in a Rabbit Model
Published on: April 3, 2016
Corneal crosslinking with riboflavin using sunlight
Emilio A Torres-Netto1, Hormoz Abdshahzadeh, Nan-Ji Lu
1From the Ocular Cell Biology Group, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland (Torres-Netto, Abdshahzadeh, Abrishamchi, Hillen, F. Hafezi); ELZA Institute AG, Dietikon, Switzerland (Torres-Netto, Abdshahzadeh, Lu, Abrishamchi, Hillen, N. Hafezi, F. Hafezi); Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil (Torres-Netto); Faculty of Medicine, University of Geneva, Geneva, Switzerland (Torres-Netto, N. Hafezi, Koppen, F. Hafezi); Faculty of Medicine and Health Sciences, University of Antwerp, Wilrijk, Belgium (Lu, Koppen); Department of Ophthalmology, Antwerp University Hospital, Edegem, Belgium (Lu); Computer Vision Laboratory, Department of Information Technology and Electrical Engineering, Swiss Federal Institute of Technology, Zurich, Switzerland (Kling); Department of Ophthalmology, University of Southern California, Los Angeles, California (F. Hafezi); School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China (F. Hafezi).
Purpose:
To assess whether sunlight might be used to induce a biomechanical stiffening effect in riboflavin-soaked corneas similar to the effect observed in corneal crosslinking (CXL) using riboflavin and UV-A light.
Setting:
Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.
Design:
Experimental study.
Methods:
52 porcine eyes were assayed. The concentration of riboflavin in the corneal stroma was estimated using UV-A transmission in a preliminary experiment. Then, the duration of sunlight exposure to achieve a fluence of 7.2/cm 2 was calculated. Finally, de-epithelialized corneas were divided equally into 3 groups and soaked with riboflavin 0.1% (control group and Group 1) or 0.5% (Group 2). Eyes from Groups 1 and 2 were then exposed to sunlight. The elastic modulus was calculated as an indicator of stiffness.
Results:
Riboflavin concentration in Group B was higher by a factor of 2.8 than Group A. According to live illuminance measurements and stromal riboflavin concentration, the sunlight exposure duration varied between 16 minutes and 45 minutes. Groups 1 and 2 had higher elastic modulus than controls ( P < .0001) but did not differ between them ( P = .194). The stiffening effect was 84% and 55%, respectively.
Conclusions:
Sunlight exposure of ex vivo corneas soaked in both riboflavin 0.1% and 0.5% resulted in increased corneal stiffness. Specifically, riboflavin 0.1% with longer UV-A exposure showed a trend for a greater stiffening effect, which might open new alleys for the use of oral riboflavin and fractioned sunlight exposure as less invasive CXL techniques.
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