Photochemical Crosslinking of Tarsal Collagen as a Treatment for Eyelid Laxity: Evaluation in Ex Vivo Human Tissue

Abstract

Purpose: Experimental investigation in human eyelids to confirm that exposing excised tarsal plates to ultraviolet-A radiation can induce a stiffening effect through the riboflavin-photosensitized crosslinking of tarsal collagen. Methods: Thirteen tarsal plates excised from nonfrozen human cadavers were irradiated with ultraviolet-A rays (365 nm wavelength) at an irradiance of 75 mW/cm2 for 3 minutes, equivalent to a radiation fluence of 13.5 J/cm2, in the presence of a riboflavin derivative as a photosensitizer. The tensile stress (strength) and Young’s modulus (stiffness) of both nonirradiated and irradiated specimens were measured with the BioTester 5000 in the uniaxial mode at a strain of 10% and analyzed statistically. Individual specimens excised from 2 cadavers were also examined by routine histopathologic protocols to assess the effect of radiation on the Meibomian glands and collagen organization. Results: The irradiation enhanced both stiffness and strength of the human tarsal specimens, the difference between the test samples and controls being statistically significant (p < 0.0002 for n = 13). Histology indicated no damage to tarsal connective tissue or to Meibomian glands, and revealed a more compact packing of the collagen network located around the glands, which may be beneficial. The existence of collagen compaction was also supported by the reduction of samples’ thickness after irradiation (p = 0.0645). Conclusions: The irradiation of tarsal tissue with ultraviolet-A light of tarsus appears to be a safe and effective method for reducing eyelid laxity in human patients.