Open Access
Photochemistry and Photobiology
First published: 27 November 2022

Safety Evaluation of Far-UV-C Irradiation to Epithelial Basal Cells in the Corneal Limbus


Sachiko Kaidzu 1, Kazunobu Sugihara 1, Masahiro Sasaki 2, Aiko Nishiaki 2, Hiroyuki Ohashi 2, Tatsushi Igarashi 2, Masaki Tanito


1 Department of Ophthalmology, Shimane University Faculty of Medicine, Izumo, Japan. 

2 Ushio Inc., Tokyo, Japan. 


We reported that Far-UVC is unlikely to cause injury because it only reaches the superficial layer of the corneal epithelium, which peels off in 24 hours due to physiological turnover. However, if the basal portion of the corneal ring, where the stem cells of the corneal epithelium reside, is injured, this may lead to corneal injury in the long term. Therefore, we investigated the effects of irradiated UV on the corneal ring. 
In the rat corneal rings immediately after 254 nm UVC and 311 nm UVB irradiation, CPD was observed up to the basal portion of the epithelium of the rings both in the upper and lower regions. 235 nm UVC showed CPD in the upper region up to the middle layer and in the lower region in the superficial layer. In contrast, at 207 and 222 nm UVC, CPD was observed only in the superficial layer of cells. In the porcine corneal ring, 222 nm UVC reached only the superficial layer of the ring epithelium. 
Since corneal epithelial stem cells reside in the basal portion of the corneal ring, Far-UVC, which only reaches the superficial layer, does not injure tissue stem cells and is unlikely to have long-term effects on corneal tissue. 



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