Behind your eye, the rod and cone cells on your retina read light so you can see. Alongside them, a third kind of cells in the retina read the same light so your body knows what to do.
This simple division of labor is the reason you can watch TV until late at night, but you might not get to sleep easily. It’s why you may memorize, learn, and solve puzzles better in sunlight than firelight. Blue light is the reason.
If your rod and cones see blue light, then these others tell your brain, “wake up, daylight’s burning!” And when blue light goes away, these cells allow melatonin to rock you to sleep again.
How To Make Blue/Not-Blue Work for You
This third type of cell called “intrinsically photosensitive retinal ganglion cells,” or ipRGCs, were discovered in the 1920s. Their effect on our biological rhythms was not clear for decades.
It may seem logical that humans became daytime creatures because we see better when the sun is up. In actuality, we become more active in sunlight or any blue light because it causes our brain to release a chemical called melanopsin. Melanopsin regulates our circadian clock and sends out nerve impulses that cause a ripple of effects. As melanopsin rises, melatonin (the sleep enzyme) falls.
Blue light is your friend when you want to study, learn, memorize, or be productive.
Several studies have shown that blue light enhances alertness and vigilance. One done at the University of Greenwich found that exposing workers to enriched blue light in the office made them happier and more productive.
Another study showed that a half hour of exposure to rich blue light while studying enhanced memory consolidation—so that items learned were retained better.
If you want to be productive or learn something, turn up those blue lights.
If you are a slow starter and need to get over your morning sluggishness, LED and fluorescent lights are the best sources of blue light waves after natural sunlight. Turn them on, even if you can see fine without them
We Need Blockers for Nighttime
Good as blue light is, it’s not helpful 24-hours around the clock.
All the while you’re in blue, your melatonin is being suppressed. That becomes an unnatural pattern when you turn on fluorescent lights, LED screens and computers late in the day and after dark.
This is why TVs and computer screens can disrupt our ability to get to sleep at night.
The irony in this is that the older you get, the less melatonin you make and the more likely you are to suffer insomnia. So just at the age when you are more likely to be settled in front of the TV instead of meeting friends in a dark bar, you are loading up on blue light that is not helping.
It takes just 10 minutes of prolonged light exposure for the melanopsin-producing cells to start the process of suppressing melatonin. Staring at your cell phone or tablet may not be hard on your eyes, but it may be having a big effect on your ability to wind down and get some sleep.
Let Melatonin Begin
We've long known what melatonin does and how to use it to encourage sleep. But until recent work at Salk Institute, the exact mechanics of the melanopsin-melatonin process has been unclear.
Like many other cells in your body, the cells in the retina can be “down-regulated,” or turned off by other chemicals called arrestins.
But the Salk Professor, Satchin Panda, found that the expected arrestin process doesn't work as expected with the melanopsin cells in the retina.
Instead of shutting down melanopsin production, the arrestin made it increase. Increased melanopsin causes wakefulness because it suppresses melatonin.
This is what matters... The new findings at Salk finally explain how your computer is keeping you awake, and, further, they could eventually lead to effective treatments for migraines, insomnia, jet lag and circadian disorders that may also play a role in obesity, insulin resistance, metabolic syndrome, and cognitive problems.
When it's daytime to your eyes, your brain will get a wake-up call, even if that light is coming from your TV screen broadcasting Jimmy Kimmel Live! around midnight.
If you are not likely to turn off the television and walk away from your computer or cell phone after dark, however, you have defenses.
The hands-down best one is to get glasses with blue-blocker lenses.
In fact, you don't need to spend $50 (nonprescription) or $300 (prescription) for help. Consumer Reports tested three brands of nonprescription blue-blocking glasses. The winner was the basic orange safety glasses. Cost $8. Go to a Home Depot near you.
The nice thing about the big orange safety glasses is that you are also protected from flying debris, should that happen around your house. Say champagne corks on New Years' Eve? But on a typical evening, they give your surroundings a lovely calming glow. It's like seeing the world by firelight.
It's a cheap fix, and it actually works.