Abstract
Exposure Limit Values (ELV) for artificial lighting were defined in order to prevent light-induced damage to the retina. The evaluation of the lighting devices include the correction of their spectra by the B(λ) function or blue light hazard function, representing the relative spectral sensitivity of the human eye to the blue light. This weighting function peaks between 435 and 440 nm. In this study we evaluate a new generation of light emitting diode (LED), the GaN-on-GaN (gallium nitride on gallium nitride) LED, that present an emission peak in the purple part of the spectrum. Wistar rats were exposed to GaN-on-GaN and conventional diodes at different retinal doses (from 2.2 to 0.5 J/cm2). We show that GaN-on-GaN diodes are more toxic than conventional LED for the rat neural retina and the rat retinal pigment epithelium, indicating that the BLH (blue light hazard) weighting is not adapted to this type of diodes. One of the reasons of this increased toxicity is the effects of shorter wavelengths on mitochondria polarization. We also show that the threshold of phototoxic retinal dose in the rat (fixed at 11 J/cm2, BLH weighted) is overestimated, suggesting that the values used for regulations, calculated in primates using the same methods than in rats, should be revised.
Highlights
Exposure Limit Values (ELV) for artificial lighting were defined in order to prevent light-induced damage to the retina
We have shown[9] that after light emitting diode (LED) exposure at doses below the recognized toxic levels, there is a permeabilization of the outer blood retinal barrier (OBRB), a feature seen in many common retinopathies[11] together with an increase of the cells size, both features related to ageing of the retinal pigment epithelium (RPE) cells[12]
At the neural retinal level we found an increase of stress markers like glial fibrilary acidic protein (GFAP) (Fig. 1A), and a decrease of antioxidant enzymes like superoxide dismutase 2 (SOD2) at the photoreceptor level (Fig. 1B)
Summary
Exposure Limit Values (ELV) for artificial lighting were defined in order to prevent light-induced damage to the retina. Exposure Limit Values (ELV), proposed by the ICNIRP (International Commission for Non-Ionizing Radiation Protection) were defined in order to prevent light-induced photochemical damage to the retina (blue light hazard). The B(λ) function, called the blue light hazard function represents the relative spectral sensitivity of the human eye to the blue light hazard It is based upon the relative spectral effectiveness of optical radiation to induce retinal photochemical injury (photic maculopathy)[1,2]. These diodes can be operated at higher current densities and produce more light from a smaller area Their short wavelength emission is shifted to the purple part of the spectrum (around 405 nm) and they use a mix of three phosphors giving a better color rendering while avoiding the blue overshoot and the cyan gap of conventional LED. The relevance of using the BLH (blue light hazard) weighting in assessing the risk group of household lighting devices is discussed
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