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New research · Ophthalmology
Photochemistry and photobiology · 3d
StudyPhotochemistry and photobiology · 2026

Human ocular-discomfort-free thresholds for 222 nm Far-UVC irradiation: A prospective interventional study.

Sachiko Kaidzu, Kazunobu Sugihara, Masaki Tanito
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OphthalmologyStudy

222 nm Far-UVC stays discomfort-free below about 5.5 mJ/cm2 total eye dose.

Human ocular-discomfort-free thresholds for 222 nm Far-UVC irradiation: A prospective interventional study.

Sachiko Kaidzu … Masaki Tanito
Photochemistry and photobiology · 2026
Purpose

The purpose of this study is to examine irradiation conditions of 222 nm Far-UVC that do not cause ocular discomfort to participants, considering both the irradiation intensity (ODF-IT; ocular-discomfort-free irradiance threshold) and irradiation dose (ODF-DT; ocular-discomfort-free dose threshold).

Methods

A prospective, single-blind interventional study was conducted with 36 healthy adults exposed to 222 nm Far-UVC under five different irradiation conditions varying in intensity and total dose, along with a visible-light control condition.

n = 36 healthy adults
5.5
Results
5.5
mJ/cm2
eye discomfort stayed absent when total light exposure remained at or below this level
n = 36 healthy adults
More results

The irradiation device, placed under the TV monitor, delivered 222 nm Far-UVC or visible light to participants viewing the video.

No adverse changes were observed in spherical equivalent refractive error, or corneal endothelial cell density under any condition.

More results

Corneal fluorescein staining occurred in some cases but showed no consistent correlation with ocular discomfort.

Discomfort was significantly associated with radiant exposure dose, video viewing time and time after video viewing.

“
Conclusion

The ODF-IT and ODF-DT values of 222 nm Far-UVC determined by the present study were around ≤1.0 μW/cm 2 and approximately 5.5 mJ/cm 2 respectively.

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