Abstract
Purpose :
The tarsus provides structure to the upper and lower eyelid and alterations in tarsus may result in floppy eyelid syndrome, entropion, or ectropion. Surgery is currently the standard treatment for these conditions, but crosslinking (CXL) has recently been proposed as an alternative therapy by changing tarsal tissue stiffness. This study used an emerging bioimaging technique, second-harmonic generation (SHG) microscopy, to examine tarsal collagen fibers ex vivo before and after crosslinking at different riboflavin concentrations. Fluorescence recovery after photobleaching (FRAP) was also performed to confirm the effects of tarsal tissue crosslinking.
Methods :
Tarsus was isolated from eighty upper eyelids of Sprague-Dawley rats. Immediately following isolation, tarsus was incubated with fluorescein isothiocyanate-dextran (FITC), then riboflavin at different concentrations (0.1%, 0.3%, 0.5%). Tissue was irradiated with ultraviolet (UV) light at 365 nm, then imaged using SHG technology. Tarsal permeability was assessed with the FRAP assay.
Results :
The organization of tarsal collagen bundles varies greatly depending on location. After crosslinking with high concentration riboflavin (0.5%), collagen fibers became more densely packed and wavier compared to untreated tarsus, but no changes were observed with the lower riboflavin concentrations. Tissue permeability was significantly decreased compared to control only in the 0.5% concentration group as well.
Conclusions :
To the authors’ knowledge, this is the first description of SHG imaging of the tarsus before and after crosslinking. This study highlights the unique and widely variable arrangement of tarsal collagen bundles in the upper eyelid and establishes the methodology to study collagen fibrils ex vivo after crosslinking. It also confirms the crosslinking effects of ultraviolet radiation on tarsus collagen.
This is a 2020 ARVO Annual Meeting abstract.