Purpose: The aim of this study was to develop a modified ex vivo corneal cross-linking method that increases stromal resistance to enzymatic degradation for use as a carrier for the Boston keratoprosthesis.
Methods: Ex vivo cross-linking of human corneas was performed using Barron artificial anterior chambers. The corneas were deepithelialized, pretreated with riboflavin solution (0.1% riboflavin/20% dextran), and irradiated with ultraviolet A (UV-A) light (λ = 370 nm, irradiance = 3 mW/cm2) for various durations. The combined effect of UV-A and gamma (γ) irradiation was also assessed using the commercially available γ-irradiated corneal donors. The corneas were then trephined and incubated at 37°C with 0.3% collagenase A solution. The time to dissolution of each cornea was compared across treatments.
Results: Deepithelialized corneas (no UV light, no riboflavin) dissolved in 5.8 ± 0.6 hours. Cross-linked corneas demonstrated increased resistance to dissolution, with a time to dissolution of 17.8 ± 2.6 hours (P < 0.0001). The corneal tissues' resistance to collagenase increased with longer UV-A exposure, reaching a plateau at 30 minutes. Cross-linking both the anterior and posterior corneas did not provide added resistance when compared with cross-linking the anterior corneas only (P > 0.05). γ-irradiated corneas dissolved as readily as deepithelialized controls regardless of whether they were further cross-linked (5.6 ± 1.2 hours) or not (6.1 ± 0.6 hours) (P = 0.43).
Conclusions: Collagen cross-linking of the deepithelialized anterior corneal surface for 30 minutes conferred optimal resistance to in vitro keratolysis by collagenase A.
*Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA; and
†Schepens Eye Research Institute, Harvard Medical School, Boston, MA.
Reprints: Joseph B. Ciolino, MD, Massachusetts Eye and Ear Infirmary, Harvard Medical School, 243 Charles St, Boston, MA 02114 (e-mail: firstname.lastname@example.org).
Supported in part by the Boston Keratoprosthesis Research Fund (Massachusetts Eye and Ear Infirmary), Boston, Massachusetts, and the National Institutes of Health, National Eye Institute, Bethesda, Maryland (NEI 1K08EY019686 to J. B. Ciolino) and an unrestricted grant to the Department of Ophthalmology, Harvard Medical School, from Research to Prevent Blindness, New York, New York.
The authors have no other conflicts of interest to disclose.
Received April 04, 2014
Accepted May 13, 2014