Photochemical Crosslinking of Eyelid Tissue by Trans-Conjunctival Exposure to UV-A Radiation: Implications for Biological Safety.

A procedure based on exposure to ultraviolet-A (UV-A) radiation is in current development for treating pathological conditions of the eyelid generated through the laxity of the tissues. By irradiating the eyelid in the presence of a photosensitizer, photochemical crosslinking of tarsal collagen is induced, leading to its mechanical reinforcement, thus preventing further laxity increase. Here, we investigated potential radiation-induced damage to the target tissues. Ex vivo specimens of ovine tarsal plates were irradiated trans-conjunctivally with UV-A radiation (365 nm) in the presence of riboflavin at increasing irradiances. The specimens were processed histologically and analyzed. Except for episodic minor conjunctival epithelial damage, there was no evidence of injury to resident cells, connective tissue, meibomian glands, or muscles. Based on in vitro histological analysis, the study demonstrated negligible tissue damage induced by irradiation with UV-A, thereby suggesting the crosslinking of tarsal collagen as a possible therapeutic approach for treating eyelid laxity.