# Comparative Study of Blue Light with Ultraviolet (UVC) Radiation on Betacoronavirus 1
## 4 Discussion
The basic parts of the eyes are the retina, cornea, pupil, lens, and conjunctiva. The pupil is the small opening that allows the light into the eye, and behind the pupil is the lens that focuses the light energy density on the retina. The superficial part of the eye is the cornea and conjunctiva. The amount of light entering the eye depends on the pupil's size. The pupil's average maximum constriction and dilation are approximately a diameter of 3 and 7 mm, respectively. This diameter is a limiting factor corresponding to the field of view (FOV). It is assumed that the pupil remains constricted to a diameter of 3 mm for visible light, whereas the pupil is dilated for wavelengths outside the visible range. The exposure time also determines the field of view. For disinfection purposes, the exposure time is more than 10,000 s. The exposed area of the retina will be approximately a FOV angle of 0.1 radians, which is over 5 degrees. By IEC 62471 [30], the skin or cornea hazard by blue light is denoted by E\({}_{\text{B}}\). The equation provided by the IEC standard for E\({}_{\text{B}}\) is for small sources, i.e., an aperture less than 0.011 [30]. The skin and cornea hazard (E\({}_{\text{B}}\)) ranges from low risk at 1.0 W.m\({}^{-2}\) and moderate risk at 400 W.m\({}^{-2}\). L\({}_{\text{B}}\) denotes retinal hazard, and the value is based on radiance (W.m\({}^{-2}\).sr). The L\({}_{\text{B}}\) limit ranges from low risk at 10,000 W/(m\({}^{2}\).sr) to moderate risk at 4,000,000 W/(m\({}^{2}\).sr). A human exposed to a light source with a radiance lower than 100 W/(m\({}^{2}\).sr) will receive a dose of greater than 10\({}^{6}\) J/(m\({}^{2}\).sr) in 10,000 s exposure time (2 h and 45 min), and this is classified as no risk [31]. If exposed to a light source of a radiance higher than 100 W/(m\({}^{2}\).sr) but less than 10,000 W/(m\({}^{2}\).sr), the person will receive a dose greater than 10\({}^{6}\) J/(m\({}^{2}\).sr) within a 100 s exposure time, this is classified as low risk [31]. The light source with a radiance that is higher than 10,000 W/(m\({}^{2}\).sr) is classified as medium to high risk, and that light source is prohibited from domestic general lighting [31]. There are many commercial lights such as vital vio [32] that have been tested for IEC 62471 and have been placed in the Exempt Group (RG O), i.e., poses no optical hazard for continuous, unrestricted exposure to humans. The skin and cornea hazard are determined by irradiance, whereas the retinal hazard is by radiance. Assuming that only domestic general visible blue light is used for disinfection means the retinal hazard is already considered. Only skin and cornea hazards must be calculated for uninterrupted disinfection purposes. For safety reasons, the betacoronavirus was used and not SARS-CoV-2, as there have been many reported accidental cases of the usage of SARS-CoV-2 [33]. This study was conducted to achieve surface disinfection through static liquid media. Air disinfection through visible light has been very briefly studied, and future work will focus on using an aerosolized medium to test the efficacy of visible light for air disinfection. Based on the results and discussed advantages of using 405 nm over UVC, the 405 nm deployment in public arenas seems pragmatic and doable. The dose used in this study is safe and can be achieved from commercially available LEDs. This technology can be used to disinfect surfaces continuously in public areas, such as hospitals, schools, aircraft cabins, and laboratories. The potential of 405 nm LED in reducing the betacoronavirus 1 is significant and should be explored further.