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Ultraviolet-A collagen cross-linking therapy: effect on the biomechanics and histology of the human cornea

Poster Details

First Author: M.Del Buey SPAIN

Co Author(s):    E. Lanchares   J. Cristobal   B. Calvo   L. Lavilla           

Abstract Details


The purpose of this experimental study is to evaluate the immediate effect of the CXL treatment on the biomechanical properties and histological microstructure of healthy human corneal tissue. With this purpose, in vitro mechanical tests and histological observation of cross-linked and untreated human corneal tissue were performed.


1 Department of Ophthalmology, “Lozano Blesa” University Clinic Hospital, Zaragoza, Spain. 2 Aragón Institute of Engineering Research (I3A) University of Zaragoza, Spain. 3 Aragon Health Sciences Institute


Mechanical tensile test and histological analysis were performed in de-epithelialized healthy human corneal tissue treated with riboflavin solution (0.01% riboflavin-5-phosphate and 20% dextranT-500) – 30 min UVA irradiation (treated sample TS). A similar study was performed to untreated de-epithelialized healthy human corneal tissue (control sample, CS). The corneas were clear and their pachymetry was between 540 and 550mm. Both histological and mechanical analyses were performed immediately after treatment. The stress-strain behaviour of the two specimens was measured to compare the corneal biomechanical properties between them.


The analysis of the stress-strain curves showed a different corneal response between treated (TS) and untreated (CS) samples. TS showed a stiffer behaviour than CS. The treated corneal tissue (TS) resulted 1.8, 1.6, 1.7 and 1.5 fold stiffer than the untreated sample (CS) at 6, 8, 10 and 12% stretch, respectively. The histological analysis of TS showed an increased fibrillar density with decrease of interlamellar space in comparison with CS. Keratocyte apoptosis was observed in TS even at deep stromal level. There is an evident absence of nuclei in the treated sample compared to the control. Interlamellar spaces correspond to the presence of a cellular body, but the nucleus could not be present at the depth of the tissue section.


The UVA-induced CXL has an immediate biomechanical and histological effect over the treated healthy human corneal tissue. Stiffening of the tissue, keratocyte apoptosis and stromal compacting were observed. The CXL treatment is not advisable for corneas with a thickness lower than 400 microns. Future studies may help to customize the parameters of the treatment in order to establish the pair intensity/ UVA-time to guarantee the application of a quantity of energy under the damage threshold.

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