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Updated: Feb 17, 2026
Three Different Protocols of Corneal Collagen Crosslinking in Keratoconus: Conventional, Accelerated and Iontophoresis
Published on: November 12, 2015
Mechanical outcome of accelerated corneal crosslinking evaluated by Brillouin microscopy
Joshua N Webb1, Johnny P Su1, Giuliano Scarcelli1
1From the Fischell Department of Bioengineering, University of Maryland, College Park, Maryland, USA.
Purpose:
To quantify corneal mechanical changes induced by corneal crosslinking (CXL) procedures of different ultraviolet-A (UVA) intensity and exposure time using Brillouin microscopy.
Settings:
University of Maryland, College Park, Maryland, USA.
Design:
Experimental study.
Methods:
Porcine cornea samples were debrided of epithelia and soaked with riboflavin 0.1% solution. Samples were exposed to a standard 5.4 J/cm2 of UVA radiation with varying intensity and exposure time as follows: 3 mW/cm2 for 30.0 minutes, 9 mW/cm2 for 10.0 minutes, 34 mW/cm2 for 2.65 minutes, and 50 mW/cm2 for 1.80 minutes. Using Brillouin microscopy, the Brillouin modulus for each sample was computed as a function of radiation intensity/exposure time. For validation, the Young's modulus was found with the stress-strain test and compared at each irradiation condition.
Results:
The standard 3 mW/cm2 irradiance condition produced a significantly larger increase in corneal Brillouin modulus than the 9 mW/cm2 (P ≤ .05), 34 mW/cm2 (P ≤ .01), and 50 mW/cm2 (P ≤ .01) conditions. Depth analysis showed similar anterior sections of the standard and 9 mW/cm2 conditions but significantly less stiffening in the central and posterior of the 9 mW/cm2 condition. The stiffening of the standard protocol was significantly larger in all sections of the 34 mW/cm2 and 50 mW/cm2 conditions (P ≤ .01). The overall change in Brillouin-derived Brillouin modulus correlated with the increase in Young's modulus (R2 = 0.98).
Conclusions:
At a constant UVA light dose, accelerating the irradiation process decreased CXL stiffening. Brillouin analysis showed that accelerated protocols were especially ineffective in the deeper portions of the cornea.
