One of the most consistent issues that we discuss is how blue light affects the retina, but do we really understand what the retina is, how it works, and how blue light affects it?
As light travels through the eye, it enters through the pupil and is focused by the lens so that it hits the retina correctly. The retina, a thin layer of tissue at the back of the eye, is what converts the light waves into information able to be processed by the brain. Light first passes through a nerve fiber layer, a layer of ganglion cells which provide blood supply to the retina, and finally land in the layer of photo-receptors, made of both rods and cones. The rod photo-receptors process peripheral vision and dim light, while the cones process color, brighter lights, and finer details.
For a long time, it has been assumed that the rods and cones were the only photo-receptor cells, however recent research has shown that there may be an additional type of photo-receptor situation within the ganglion layer, “intrinsically photosensitive retinal ganglion cells” (ipRGC). These cells have been shown to independently control pupil dilation and contraction. Not coincidentally, these cells have their most noticeable response at high wavelengths of light- blue length. Learn More about the Anatomy of the Retina and Blue Light Hazards
So we know that the retina is essential to our eyes processing blue light, but why does high energy visual light affect the retina differently than other ranges?
The retina is equipped with several different mechanisms to combat the strain of high energy light on its tissues, however, overexposure in either duration or intensity of light can produce what is known as a “thermoelastic pressure wave.” Because light is waves of energy, when the chemical and mechanical protection mechanisms of the retina cannot handle the waves it creates this physical wave or ripple across the retina, and “tissue is disrupted by shear forces or by cavitation.” Learn More about Phototoxicity
To sum it up, our retinas are designed to handle the strains of the natural sun cycle. They are well designed to accommodate the energy levels of the far away sun and the intensity of daylight. When we expose them to long durations of blue light or intense blue light, the high energy light overloads the retina and may cause physical damage that manifests as digital eye strain and may even up our risk of long term damage.