Part 2: Blue light and The Brain
In the retina, there are special cells called retinal ganglion cells (RGCs), which are sensitive to blue light, and they relay information to the brain to control our circadian rhythm a.k.a. the sleep/wake cycle.
Before the days of computers and mindless phone scrolling, our exposure to blue light at night time was relatively low. Daytime blue light exposure (from the sun) travels from the eyes, to the RGCs, then to the brain’s internal clock, called the suprachasmatic nucleus (SCN). The SCN signals to the pineal gland to STOP secreting melatonin, which helps to wake us up! Then, in the evening, as blue light levels decreased (as the sun goes down) the SCN allows the pineal gland to release melatonin, and we feel sleepy! But nowadays, with exposure to screens and fluorescent light bulbs well into the evening, we aren’t getting that natural dose of melatonin, and it’s harder to fall asleep. People these days are sleeping fewer hours than generations before.
A small amount of blue light is actually beneficial to our brains. It helps us to wake up in the morning, and also combats Seasonal Affective Disorder. Kids need a small amount (from the sun - not digital devices) in order for their eyes to develop properly, and to prevent nearsightedness. However, with long hours on digital devices, it is important to protect the eyes against the unnatural blue light exposure. We typically recommend that people put on their blue light blocking lenses around mid-day, to soothe the eyes and help maintain the natural sleep/wake cycle.