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Low-fluence corneal cross-linking induces the same biomechanical stiffening as the standard Dresden protocol

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Session Details

Session Title: Presented Poster Session: Cornea IV

Venue: Poster Village: Pod 3

First Author: : S.Kling SWITZERLAND

Co Author(s): :    E. Torres Netto   F. Hafezi           

Abstract Details


Currently used corneal cross-linking (CXL) protocols vary in irradiance and time, but share the same total fluence of 5.4 J/cm2. Although this fluence is considered safe, reducing the UV fluence while maintaining biomechanical efficacy would be beneficial: it would further reduce radiation exposure, and could allow treatment in corneas thinner than 400 µm.


Experimental laboratory study, Laboratory of Ocular Cell Biology, CABMM, University of Zurich, Switzerland


Thirty-four freshly enucleated porcine corneas were de-epithelialized and soaked with 0.1%-hypoosmolar riboflavin solution during 30 minutes. Low-fluence CXL (30 min at 1.5 mW/cm2, fluence 2.7 J/cm2) was compared to standard CXL (30 min at 3 mW/cm2, fluence 5.4 J/cm2). Controls were soaked with riboflavin, but not exposed to UV light. Elastic (stress-strain) and viscoelastic (stress-relaxation) bi-dimensional testing was performed with a commercial stress-strain extensometer to quantify the biomechanical stiffening effect.


Corneas cross-linked with low and standard UV irradiances had a significantly (p<0.001) higher elastic modulus (65.9±15.7 MPa and 67.1±15.6 MPa, respectively) when compared to controls (52.4±12.3 MPa). Also, the remaining stress after 120s of stress-relaxation was significantly (p≤0.013) higher after CXL with low and standard UV irradiances (159±21 kPa and 158±25 kPa, respectively) compared to controls (135±20 kPa). Between CXL conditions, no difference (p=0.64) was observed with low and standard irradiances.


The UV fluence for CXL may be reduced while maintaining the biomechanical efficacy by using a lower UV irradiance and the same irradiation duration. This may open alleys in the treatment of extremely thin corneas.

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