We know that sunlight can be dangerous for the eyes if we do not protect ourselves from it. It is notably responsible for the appearance and progression of age-related macular degeneration (AMD).
Old standards
But natural light is not the only thing that harms our good visual health. “It is particularly established that blue light, emitted in particular by LEDs, damages retinal cells and causes sleep disorders and other abnormalities associated with dysregulation of the circadian rhythm”notes the National Institute of Health and Medical Research (Inserm) in a recent article.
To protect us from the effects of artificial light, standards were established almost 40 years ago. However, according to Alicia Torriglia, researcher at Inserm, these standards are obsolete and the doses, expressed in joules per cm2, at which artificial lighting has been deemed dangerous, are largely overestimated.
White light made up of different colors
Natural or artificial, white light combines rays of different colors, each corresponding to a specific wavelength.
Each light Source combines different colors at varying wavelengths. The toxicity of light therefore depends on its intensity but also on the wavelengths of which it is composed.
- Blue light : in the 1980s, the International Commission on Non-Ionizing Radiation Protection set limit values for exposure to the retina.
Exposure is thus considered harmful from 11 joules/cm² in rodents, from 22 joules/cm² in primates.
However, the recent Inserm study, published in International environmentshows much lower tolerance thresholds.
“ We had to interrupt our experiments a third of the time planned, so as not to cause suffering to the animals exposed to light which nevertheless respected the established thresholds. », Underlines Alicia Torriglia, cited by Inserm. “ The limit of 11 J/cm² for blue light is clearly overestimated for rats, which suggests that this is surely also the case for primates and humans. »
- The green light : The study also suggests that green light causes deleterious effects on the eye, with an invasion of the retina by pro-inflammatory cells eight times greater than blue light
- The red light : The latter present in incandescent bulbs, replaced by LEDs by decision of the European Union, would on the contrary reduce the loss of photoreceptors, the sensitive cells of the retina.
Review the regulatory thresholds?
For Alicia Torriglia, all of the regulatory exposure thresholds should be reviewed. She adds : ” The effect of light on the retina is complex, it depends not only on the quantity, but also on the timing of exposures. The retina has a circadian rhythm and its sensitivity during the day is not the same as at night. Physiological changes that occur at night make it more sensitive to light and more subject to phototoxic stress.”
Inserm therefore warns against LEDs and screens in the evening and at night, especially among children, who have lower sensitivity thresholds than those of adults.
