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Ex vivo thermographic analysis of the eyelid conjunctival surface during ultraviolet A-mediated photochemical crosslinking of tarsal collagen: A step in translational safety evaluation

Shuko Suzuki1 ,  Nadja E. Pop2,3 ,  Alexandra I. Manta1,2,3,4 ,  Traian V. Chirila1,2,3,5*
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1 Queensland Eye Institute, Woolloongabba, Queensland, Australia
2 Center for Advanced Medical and Pharmaceutical Research, George E. Palade University of Medicine, Pharmacy, Sciences and Technology, Târgu Mureş, Mureș, Romania
3 Faculty of General Medicine, George E. Palade University of Medicine, Pharmacy, Sciences and Technology, Târgu Mureş, Mureș, Romania
4 Faculty of Health and Behavioural Sciences, University of Queensland, St Lucia, Queensland, Australia
5 Australian Institute of Bioengineering and Nanotechnology, University of Queensland, St Lucia, Queensland, Australia
Global Translational Medicine, 025410078 https://doi.org/10.36922/GTM025410078
Received: 10 October 2025 | Revised: 24 November 2025 | Accepted: 18 December 2025 | Published online: 20 January 2026
© 2026 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

Ultraviolet A (UVA)-induced collagen crosslinking can mechanically reinforce collagenous tissues and is being translated as a minimally invasive treatment for pathological eyelid laxity, yet the extent of irradiation-related heating at the conjunctival–tarsal interface remains unclear. In this study, we developed a novel procedure to treat pathological eyelid laxity. The methodology is based on the photocrosslinking of tarsal collagen, leading to mechanical reinforcement of the entire eyelid. In our previous studies, exposure to ultraviolet A (UVA) radiation at fluences below 20 J/cm2 did not cause histopathological alterations to the eyelid tissues. Here, we further evaluated biological safety by quantifying conjunctival surface temperature increases during UVA irradiation to inform clinical translation. Using ex vivo sheep eyelids as a model, we used infrared thermography to measure the temperatures attained on the tarsal conjunctival surface during UVA irradiation (365 nm) at four irradiances for a maximum exposure time of 3 min, corresponding to fluences of 8.1, 13.5, 27, and 45 J/cm2. Both the exposure time and irradiance caused an asymptotic increase in temperature, while a linear dependence was observed between fluence and temperature increase (ΔT). The recorded values for ΔT ranged from 3.3°C to 14.0°C. In summary, at clinically practicable fluences (<20 J/cm2), such increments are not expected to raise the final temperature to the threshold for collagen denaturation and tissue damage.

Keywords
Eyelid laxity
Tarsal collagen
Photochemical crosslinking
Ultraviolet A radiation
Infrared thermography
Thermal damage
Funding
None.
Conflict of interest
The authors declare that they have no competing interests.
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