7 Blue Light Facts: How Blue Light Affected Your Eyes
Key points about blue light
Like ultraviolet radiation, visible blue light — the portion of the visible light spectrum with the shortest wavelengths and highest energy — has both benefits and dangers. Here are important things you should know about blue light:
1. Blue light is everywhere.
Sunlight is the main source of blue light, and being outdoors during daylight is where most of us get most of our exposure to it. But there are also many man-made, indoor sources of blue light, including fluorescent and LED lighting and flat-screen televisions.
Most notably, the display screens of computers, electronic notebooks, smartphones, and other digital devices emit significant amounts of blue light.
The amount of HEV light these devices emit is only a fraction of that emitted by the sun. But the number of time people spend using these devices and the proximity of these screens to the user's face have many eye doctors and other health care professionals concerned about possible long-term effects of blue light on eye health.
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2. HEV light rays make the sky look blue.
The short-wavelength, high-energy light rays on the blue end of the visible light spectrum scatter more easily than other visible light rays when they strike air and water molecules in the atmosphere. The higher degree of scattering of these rays is what makes a cloudless sky look blue.
3. The eye is not very good at blocking the blue light.
Anterior structures of the adult human eye (the cornea and lens) are very effective at blocking UV rays from reaching the light-sensitive retina at the back of the eyeball. In fact, less than one percent of UV radiation from the sun reaches the retina, even if you aren't wearing sunglasses.
(Keep in mind, though, that sunglasses that block 100 percent of UV are essential to protect these and other parts of the eye from damage that could lead to cataracts, snow blindness, a pinguecula and/or pterygium, and even cancer.)
On the other hand, virtually all visible blue light passes through the cornea and lens and reaches the retina.
4. Blue light exposure may increase the risk of macular degeneration.
The fact that blue light penetrates all the way to the retina (the inner lining of the back of the eye) is important because laboratory studies have shown that too much exposure to blue light can damage light-sensitive cells in the retina.
This causes changes that resemble those of macular degeneration, which can lead to permanent vision loss.
Although more research is needed to determine how much natural and man-made blue light is "too much blue light" for the retina, many eye care providers are concerned that the added blue light exposure from computer screens, smartphones, and other digital devices might increase a person's risk of macular degeneration later in life.
5. Blue light contributes to digital eye strain.
Because short-wavelength, high energy blue light scatters more easily than other visible light, it is not as easily focused. When you're looking at computer screens and other digital devices that emit significant amounts of blue light, this unfocused visual "noise" reduces contrast and can contribute to digital eye strain
Research has shown that lenses that block blue light with wavelengths less than 450 nm (blue-violet light) increase contrast significantly. Therefore, computer glasses with yellow-tinted lenses may increase comfort when you're viewing digital devices for extended periods of time.
6. Blue light protection may become even more important after cataract surgery.
The lens in the adult human eye blocks nearly 100 percent of the sun's UV rays. As part of the normal aging process, the eye's natural lens eventually blocks some short-wavelength blue light as well — the type of blue light most likely to cause damage to the retina and lead to macular degeneration and vision loss.
If you have cataracts and are about to have cataract surgery, ask your surgeon what type of intraocular lens(IOL) will be used to replace your cloudy natural lens, and how much blue light protection the IOL provides.
After cataract surgery, you might benefit from eyeglasses that have lenses with a special blue light filter — especially if you spend long hours in front of a computer screen or using other digital devices.
7. Not all blue light is bad.
So, is all blue light bad for you? Why not block all blue light, all the time?
Bad idea. It's well documented that some blue light exposure is essential for good health. Research has shown that high-energy visible light boosts alertness, helps memory and cognitive function, and elevates mood.
In fact, something called light therapy is used to treat the seasonal affective disorder (SAD) — a type of depression that's related to changes in seasons, with symptoms usually beginning in the fall and continuing through winter.
The light sources for this therapy emit a bright white light that contains a significant amount of HEV blue light rays.
Also, blue light is very important in regulating circadian rhythm — the body's natural wakefulness and sleep cycle. Exposure to blue light during daytime hours helps maintain a healthy circadian rhythm.
But too much blue light late at night (reading a novel on a tablet computer or e-reader at bedtime, for example) can disrupt this cycle, potentially causing sleepless nights and daytime fatigue.
If you are using your phone constantly — especially if you use it primarily for texting, e-mailing and web browsing — a convenient way to reduce your blue light exposure is to use a blue light filter.
These filters are available for smartphones, tablets, and computer screens and prevent significant amounts of blue light emitted from these devices from reaching your eyes without affecting the visibility of the display. Some are made with thin tempered glass that also protects your device's screen from scratches.
With protective lenses, blue-screen/blue-light glasses reduce digital eye strain caused by blue light. Here are some more top benefits of these amazing glasses:
- Alleviate eye discomfort.
- Improve sleep habits.
- Fight against AMD.
By wearing blue-screen/blue-light glasses while on the computer and taking other steps to limit your exposure to blue light, you can improve your overall eye health.
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Notes and References
The lowdown on blue light: good vs. bad, and its connection to AMD. Review of Optometry. February 2014.
The role of UV damage in ocular disease. Review of Optometry. October 2012.
The contrast sensitivity function measured under blue haze conditions. Investigative Ophthalmology & Visual Science. March 2012.
Retinal light toxicity. Eye. January 2011.
Superior short-wavelength contrast sensitivity in asthenopics during reflexive readjustments of ocular accommodation. Ophthalmic & Physiological Optics. July 2007.
Contrast is enhanced by yellow lenses because of selective reduction of short-wavelength light. Optometry and Vision Science. February 2000.