Induction Of Cross-Links In Corneal Tissue By Sunlight Exposure And Oral Riboflavin Administration In Rabbits: The Biomechanical Impact Using Extensometry And High-Resolution Oct Elastography
Published 2023 - 41st Congress of the ESCRS
Reference: PP14.03 | Type: Free paper | DOI: 10.82333/v1w0-gz28
Authors: Emilio A. Torres-Netto* 1 , Sabine Kling 2 , M. Enes Aydemir 3 , Nanji Lu 4 , Nikki Hafezi 3 , Mark Hillen 4 , Farhad Hafezi 1
1ELZA Institute & University of Zurich,Dietikon/Zurich,Switzerland, 2OPTIC Team, Computer Vision Laboratory,ETH Zurich,Zurich,Switzerland, 3ELZA Institute,Dietikon/Zurich,Switzerland, 4ELZA Institute,Zurich,Switzerland
Purpose
The range of sunlight extends from the UV-C spectrum to the infrared, including UV-A at 365 nm. Previous experiments have shown that ex vivo exposure of isolated porcine corneas soaked in riboflavin leads to a stiffening effect similar to the one observed in classic corneal cross-linking. Here, we assessed whether long-term administration of oral riboflavin, combined with extended exposure to natural sunlight may lead to a stiffening effect in the corneas of free-moving rabbits. Biomechanical changes were analyzed using OCT elastography and stress-strain extensometry.
Setting
Methods
16 Male New Zealand White rabbits were used. First, 4 rabbits received riboflavin orally and stromal riboflavin concentration was estimated. 12 additional rabbits were divided into two groups: the riboflavin group received vitamin B2 and sunlight exposure while the control group was exposed to sunlight only. Similar to a recent in vivo case report, a total light dosage of 2700 klux*h was targeted. To account for the light energy absorbed by the stroma, the spectral absorbance of riboflavin and the emission spectrum of sunlight were considered. OCT elastography was conducted by applying a 5 mmHg change in ambient pressure. The cornea was analyzed using stress-strain extensometry.
Results
After relaxation, control, and riboflavin conditions had a stress of 152±11.5kPa and 146±7.0kPa (p=0.57). The mean elastic modulus between 0.1 and 0.2 strain was 4.1 and 4.0 MPa (p=0.870). In elastography, the posterior half of the riboflavin cornea presented a higher strain amplitude compared to the control cornea (8.1‰ versus 3.8‰, p=0.03) suggesting a lower stiffness in the former.
Conclusions
Oral riboflavin and reduced sunlight exposure in vivo did not significantly improve the corneal stiffness of rabbit corneas. Interestingly, animals that received riboflavin and were exposed to sunlight showed a trend toward softening in the posterior corneal stroma.