Blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood—seem to be the most disruptive at night.
Research on rhesus monkeys, conducted decades ago, found that exposing the retina to the light of ophthalmoscopes produces retinal lesions and damages the retinal pigment epithelium after 15 minutes
Additional evidence is accumulating indicating that blue light is also toxic to the human retina. Braunstein and Sparrow, looking at blue and green light exposure on cultured human pigment epithelial cells, found that blue light exposure led to cell death, while placing a blue blocking filter over the cells, protected them. Furthermore, they found that only blue light caused cell damage; there was no adverse effect to the cells when they were exposed to green light
Epidemiological studies of the impact of light on the retina have produced conflicting results.
Of course, we do not see any immediate detrimental effect of blue light damage after an ophthalmic examination. However, we must realise that a cascade effect of cellular changes is induced when blue light strikes the retina. In an animal model researching exposure to blue light and photoreceptor apoptosis, the most pronounced cell death was found to occur 16 hours after exposure