Highlights:LED light induces oxidative stress and retinal injury.LED light induces photoreceptors death by necrosis and apoptosis. 2The blue component of LED is the major cause of retinal damage.3 Abstract Background: Spectra of "white LED" are characterized by an intense emission in the blue

Ageing and alteration of the functions of the retinal pigment epithelium (RPE) are at the origin of lost of vision seen in age‐related macular degeneration (AMD). The RPE is known to be vulnerable to high‐energy blue light. The white light‐emitting diodes (LED) commercially available have relatively high content of blue light, a feature that suggest that they could be deleterious for this retinal cell layer. The aim of our study was to investigate the effects of “white LED” exposure on RPE. For this, commercially available white LEDs were used for exposure experiments on Wistar rats. Immunohistochemical stain on RPE flat mount, transmission electron microscopy and Western blot were used to exam the RPE. LED‐induced RPE damage was evaluated by studying oxidative stress, stress response pathways and cell death pathways as well as the integrity of the outer blood–retinal barrier (BRB). We show that white LED light caused structural alterations leading to the disruption of the outer blood–retinal barrier. We observed an increase in oxidized molecules, disturbance of basal autophagy and cell death by necrosis. We conclude that white LEDs induced strong damages in rat RPE characterized by the breakdown of the BRB and the induction of necrotic cell death.

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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/cm 2). 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/cm 2 , BLH weighted) is overestimated, suggesting that the values used for regulations, calculated in primates using the same methods than in rats, should be revised. 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). These limits were used in the EN NF 62471 standard that define four groups of photobiological risk for incoherent (non laser) light sources ranging from risk group 0, concerning light sources delivering a retinal dose up to 2.2 J/cm 2 in 10 000 s, that are thought to be no risk, to risk group 3 for which an exposure of 0.25 s or less might be harmful for the retina. It is worth noticing that the retinal dose corresponds to the amount of blue light reaching the retina. Actually, the spectra of the measured lighting devices is corrected using the B(λ) function. The B(λ) function, also 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. This weighting function peaks near 445 nm and has a profile close to the sensitivity of shortwave cones. The attenuation of sensitivity for shorter wavelength visible light (<440 nm) is caused by the absorption of the lens of the eye and the cornea 3. Most of currently used LED are Gallium Nitride-based (GaN) grown on top of sapphire or silicon substrate. In the last few years a new LED technology was developed using GaN substrates, generating GaN-on-GaN diodes (gallium nitride on gallium nitride) 4. The use of the GaN substrate greatly improves the light emission. These diodes can be operated at higher current densities and produce more light from a smaller area. Their short wavelength em...

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