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Invest Ophthalmol Vis Sci. 2011 Nov 29;52(12):9275-8. doi: 10.1167/iovs.11-8155.

Cross-linking with ultraviolet-a and riboflavin reduces corneal permeability.

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  • 1Department of Ophthalmology, University of California, San Francisco, San Francisco, California 94143-0730, USA.



To investigate the effect of cross-linking treatment on corneal permeability in a live animal model.


Rabbit eyes were selected at random to be left unoperated or to undergo epithelial debridement with or without treatment consisting of cross-linking (CXL) with riboflavin and ultraviolet-A. Nine eyes received a total dose of 3.6 J/cm² and after epithelial healing the corneas were placed in a two-chamber system for quantification of the diffusion of fluorescein compared with controls. Thirty eyes received a total dose of 5.4 J/cm² and, after epithelial healing, in vivo corneal permeability was quantified as the pupillary response over a 30-minute period to a dose of topical pilocarpine compared with controls.


In the ex vivo assay, the mean permeability coefficient in the CXL group (2.42 × 10⁻⁷) was reduced when compared with the unoperated controls (3.73 × 10⁻⁷; P = 0.007) and to the eyes that received epithelial debridement alone (3.74 × 10⁻⁷; P = 0.01). In the in vivo permeability assay, the change in pupillary diameter at 30 minutes after pilocarpine administration was smaller in the CXL group (-1.9 mm), compared with the epithelial debridement group (-2.6 mm; P < 0.001) and with the unoperated controls (-2.7 mm; P = 0.003).


Corneal cross-linking with ultraviolet-A and riboflavin results in a statistically significant reduction in corneal permeability. These findings suggest that dosing of topical medications may need to be increased in eyes with a history of CXL to achieve expected therapeutic effects, and they may have implications for the long-term health of the cornea.

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