Visible light is much more complex than you may have thought - from Stepping outdoors into direct sunlight or flipping on a light switch indoors; to turning on your computer, phone or any digital device — all of these things result in your eyes being exposed to a variety of visible and invisible light rays that can have a range of effects on our eyes. Most people know that sunlight contains visible light rays and also invisible UV that can tan or burn the skin. But what many don't know is that the visible light emitted by the sun comprises a range of different-colored light rays that contain different amounts of energy.
UV and it’s benefits -UV rays have higher energy than visible light rays, which makes them capable of producing changes in the skin that create a suntan. Tanning booths work off this principle, but too much exposure to UV causes a painful sunburn — and even worse, can lead to skin cancer. These rays also can cause sunburned eyes — a condition called photokeratitis or snow blindness. UV, in moderation, also has beneficial effects, such as helping the body produce healthy amount of vitamin D.Without getting into the light spectrum and optics, it’s fair to say that approximately one-third of all visible light is considered high-energy visible or "blue" light.
Let’s talk 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 emission. Computers, electronic notebooks, smartphones and other digital devices emit significant amounts of blue light.
The amount of High energy light these devices emit is only a fraction of that emitted by the sun, but the amount of time people spend using these devices and the proximity of these screens to the user's face have many doctors and health care professionals concerned about possible long-term effects of blue light on eye health.
2. The eye is not very good at blocking blue light.
Anterior structures of eye are very effective at blocking UV rays from reaching the light-sensitive retina. at the back of the eye. In fact, less than one percent of UV radiation from the sun reaches the retina, even if you aren't wearing sunglasses.
Sunglasses are still required to protect the same and they parts of the eye from damage ( pterygium, pingueculae and cancer).
On the other hand, virtually all visible blue light passes through the cornea and lens and reaches the retina.
3. 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 central vision compromise.
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 may increase a person's risk of macular degeneration later in life.
4 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. As a result, when you're looking at computer screens, or any digital device that emits significant amounts of blue light, it creates visual strain.
Research has shown that lenses that block blue light with wavelengths less than 450 nm (blue-violet light) increase contrast significantly. Thus, computer glasses with yellow-tinted lenses may increase comfort when you're viewing digital devices for extended periods of time.
5. Blue light protection may be 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 because of its “ yellowing”. t
If you have cataracts and are about to have cataract surgery, ask your ophthalmologist what type of IOL will be used to replace your cloudy natural lens, and how much blue light protection the IOL provides.
After cataract surgery, it may benefit you to use a blue filter pair of glasses, especially if you spend long hours in front of a computer screen or using other digital devices.
7. Not all blue light is bad.
It's well known, 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 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 bright white light that contains a significant amount of High energy blue light rays.
Blue light is also very important in regulating circadian rhythm — the body's natural wakefulness and sleep cycle. Exposure to blue light during daytime hours helps maintain a healthful 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. This is why it’s important to put those devices away an hour before bedtime.
Blue light filters
Computer glasses can be helpful to reduce blue light exposure from computers and other digital devices. These glasses are available without a prescription if you have no need for vision correction or if you routinely wear contact lenses to correct your eyesight.
Or computer glasses can be specially prescribed to optimize your vision specifically for the distance from which you view your devices.
You also may want to consider transition lenses which provide seamless protection from UV and blue light both indoors and out and also automatically darken in response to UV rays outdoors to increase comfort and reduce glare.
Ask your eye doctor or optician which type of vision correction and lens features best suit your needs for viewing your computer and other digital devices and protecting your eyes from blue light.