When you look at the light scattered by a prism you can see the colors spread out from red to orange, yellow, green and then the blue end of the spectrum: blue, indigo and violet. Light in the visible spectrum has a range of wavelengths and energy. Wavelengths are longer and energy is less on the red end of the spectrum and wavelengths are longer with more energy on the blue end. Excessive light energy entering the eye can cause damage. Keep this fact in mind as you read on. The truth about blue light is that it is good for you but too much blue light can be bad as well.
Sunlight on a bright summer day is white light. This is because when you add all of the colors of the visible spectrum together, the eye seems them as white. And, there is more to sunlight. We know that there is UV (ultraviolet) light in sunlight which is why we get a tan from exposure to sunlight. And, it is why we get sunburned from too much exposure. Pretty much everyone knows not to look directly into the sun so it is rare for folks to burn their retina at the back of the eye. And, UV light exposure on the skin helps produce vitamin D for strong bones!
However, next to ultraviolet light, blue light is high in energy, and with cumulative exposure can cause damage to the cells in the retina at the back of the eye. And, while we do not look directly into the sun, we do often look directly at things that have a relatively high amount of blue light. You may have already guessed that we are talking about digital device screens. Everything from your home TV set and desktop computer to the laptop your child uses at school and the smartphone he or she uses to chat all night long with friends, emit blue light.
Again, looking at computer tablets does not provide the intensity of exposure to blue light that one gets from looking into the sun. But, no one would be able to look directly at the sun for hours at a time, day after day, for years. However, we live in a digital age and children, especially, are exposed early and will be exposed for years to blue light emissions from their digital devices.
So, why do you wake up in the morning? Medical scientists have looked at the physiology of sleeping and waking, often because of folks who have trouble sleeping or staying awake. What they have found is that the human brain secretes a substance called melatonin.
The natural hormone melatonin is secreted by the pineal (pih-knee-uhl) gland. This tiny gland attached to the bottom side of the brain is switched on to produce melatonin by the absence of sunlight, especially the energetic blue part of the spectrum. And, when we arise in the morning to a bright day, melatonin production turns off.
And, melatonin helps us sleep. Unfortunately, when we watch TV up close or especially when we stare into our digital device screen in the hours preceding our normal bedtime, we may well delay the secretion of melatonin and not be able to get to sleep. And, of course, if we keep looking at the digital device screen (because we cannot sleep) we simply delay our rest even longer. (See the National Sleep Foundation for further information).
So, if your child is not sleeping well and also playing video games or otherwise looking directly at their digital device screen until all hours of the night, a good house rule will be to restrict their use in the two to three hours before bedtime.
Being the most energetic part of the light spectrum, blue light is responsible for a greater number of issues relating to computer use such as digital eye strain. Digital eye strain presents as visual difficulty and discomfort of the eyes and occurs when people spend a long time at their computer, smartphone, or tablet. Part of this is because we do not blink normally when using these devices so our eyes dry out. We also remain focused close to the eyes instead of looking into the distance. And, part of this in many cases may well be the energy of blue light from the digital device screen.
Because short wavelength, more energetic blue light waves scatter more readily when passing through the atmosphere, they give the sky its blue color. At sundown when a high-pressure system is moving in and there are dust particles trapped in the air, they block the blue light and the sky appears red at sunset.
Looking directly at the sun is a bad idea. But, so is looking at a computer or smartphone screen for hours on end without some degree of protection. The long term concern with blue light and digital devices is a condition called macular degeneration. The macula is the center of the retina in the back of the eye. It is also the area of the eye which has the best vision. Macular degeneration has always been a disease of the elderly that steals their vision and causes central visual field blindness. It is the result of years of damage from energetic light waves. The concern today is that we are exposing our children to greater amounts of high energy blue light than have been seen in any previous generation. Thus, there would appear to be a greater risk of eye damage, macular degeneration, and at an earlier age than ever seen before. What can you do about this?
As we can see, blue light is important to waking and sleeping and even ultraviolet helps us produce vitamin D. But, the cumulative effect of blue light may be dangerous over the long term. And, while the cornea and lens of the eye do a good job of blocking UV light, the eye is not good at blocking blue light. This is because we need some blue light and for all of human history until the last generations, there were no computers or other digital devices!
It is unlikely that we will give up computers, smartphones, etc. Rather, we can protect our eyes and those of our children with protective eyewear. There are protective lenses for folks who need glasses because of refractive errors and there are protective lenses with no refraction but the ability to reduce passage of blue light.
For more help with choosing the protective lenses you need to protect your children’s eyes, you can shop right here.
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