Abstract
Purpose :
Currently, the evaluation of the phototoxicity of light sources focuses on their blue component. Light spectra are weighted using the Blue Light Hazard (BLH) curve that peaks at 445nm. Thus, the blue component is considered as the only source of phototoxicity. The other wavelengths of the spectrum, such as green or red, are assumed to be non-toxic for the retina. In addition, the phototoxicity threshold for blue light at 445nm is used to define the limit exposure value (LEV) and corresponds to an energetic retinal dose of 11J/cm2 for rodents. Here, we aim to evaluate the state that only blue wavelengths are phototoxic and the pertinence of the current LEV.
Methods :
Male Wistar rats were exposed to light-emitting diodes (LED) displaying different wavelengths and at various retinal doses. Damages induced by light exposure were evaluated by immunostaining and TUNEL staining on retina sections or flat mounts of the retinal pigmented epithelium (RPE).
Results :
We show that at a retinal dose 20-fold lower than the phototoxicity threshold, blue and white LED induce a significant retinal degeneration characterized by rod demise. When analyzing cell death and oxidative stress after exposure to LED, BLH-weighted retinal doses of 0.2 J/cm2 and 0.02 J/cm2 for blue and white LED respectively constitute the thresholds at which almost no damage is observed. Moreover, addition of a red component, by simultaneous exposure of rats to white and red LED, significantly decreases photoreceptor cell death. LED-induced damages are also observed in the RPE with changes in the RPE cell structure and size, and patches accumulation of rhodopsin aggregates.
Conclusions :
Taken together these results suggest that the phototoxicity threshold for rat could be overestimate by a factor of 50. Moreover, we note differences in the effects of blue and white LED at similar retinal doses, highlighting the negative impact of the other wavelengths contained in white light on phototoxicity. Also, the protective effect of the red component underlines the different effects of each part of the spectrum, indicating that the evaluation of phototoxicity should not be restricted to the blue part of the spectrum. Thus, the use of the BLH weighting to assess the LEV must be reconsidered.
This is a 2021 ARVO Annual Meeting abstract.