blue light by optom faslu muhammed

1. BLUE LIGHT: IT'S BOTH BAD AND
GOOD FOR YOU
Visible light is much more complex than you might think.
Stepping outdoors into sunlight; flipping on a wall switch indoors; turning on your
computer, phone or other digital device — all of these things result in your eyes
being exposed to a variety of visible (and sometimes invisible) light rays that can
have a range of effects.
Most people are aware that sunlight contains visible light rays and also
invisible ultraviolet rays 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.
What Is Blue Light..?
Sunlight contains red, orange, yellow, green and blue light rays and many shades
of each of these colors, depending on the energy and wavelength of the individual
rays (also called electromagnetic radiation). Combined, this spectrum of colored
light rays creates what we call "white light" or sunlight.

2. Without getting into complicated physics, there is an inverse relationship
between the wavelength of light rays and the amount of energy they contain.
Light rays that have relatively long wavelengths contain less energy, and those
with short wavelengths have more energy.
Rays on the red end of the visible light spectrum have longer wavelengths and,
therefore, less energy. Rays on the blue end of the spectrum have shorter
wavelengths and more energy.
The electromagnetic rays just beyond the red end of the visible light spectrum are
called infrared — they are warming, but invisible. (The "warming lamps" you see
keeping food warm at your local eatery emit infrared radiation. But these lamps
also emit visible red light so people know they are on! The same is true for other
types of heat lamps.)
On the other end of the visible light spectrum, blue light rays with the shortest
wavelengths (and highest energy) are sometimes called blue-violet or violet light.
This is why the invisible electromagnetic rays just beyond the visible light
spectrum are called ultraviolet (UV) radiation.

3. THE PERILS AND BENEFITS OF UV
UV rays have higher energy than visible light rays, which makes them capable of
producing changes in the skin that create a suntan. In fact, the bulbs in tanning
booths emit a controlled amount of UV radiation specifically for this reason.
But too much exposure to UV causes painful sunburn — and even worse, can lead
to skin cancer. These rays also can cause sunburned eyes — a condition called
photokeratitis or snow blindness.
But ultraviolet radiation, in moderation, also has beneficial effects, such as
helping the body manufacture adequate amounts of vitamin D.
Blue light contributes to digital eye strain; computer glasses
that block blue light may increase comfort.
Generally, scientists say the visible light spectrum comprises electromagnetic
radiation with wavelengths ranging from 380 nanometers (nm) on the blue end of
the spectrum to about 700 nm on the red end. (By the way, a nanometer is one
billionth of a meter — that's 0.000000001 meter!)
Blue light generally is defined as visible light ranging from 380 to 500 nm. Blue
light sometimes is further broken down into blue-violet light (roughly 380 to 450
nm) and blue-turquoise light (roughly 450 to 500 nm).
So approximately one-third of all visible light is considered high-energy visible
(HEV) or "blue" light.
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:
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-

4. made, indoor sources of blue light, including fluorescent and LED lighting and flat-
screen televisions.
Most notably, the display screens of computers, electronic notebooks, smart
phones 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 amount 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.
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.
THE EYE IS NOT VERY GOOD AT BLOCKING 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.
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.

5. 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, smart
phones and other digital devices might increase a person's risk of macular
degeneration later in life.
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.
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 — 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.

6. 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 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 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 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.
BLUE LIGHT FILTERS AND PROTECTIVE EYEWEAR
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 smart phones, 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.
Examples of blue light filters for digital devices include: Eyesafe (Health-E),
iLLumiShield, Retina Shield (Tech Armor), Retina Armor (Tektide), Frabicon and
Cyxus.
As mentioned above, computer glasses also can be helpful to reduce blue light
exposure from computers and other digital devices. These special-purpose glasses
are available without an eyeglass prescription if you have no need for vision
correction or if you routinely wear contact lenses to correct your eyesight. Or they

7. can be specially prescribed to optimize your vision specifically for the distance
from which you view your devices.
If you have presbyopia and routinely wear progressive lenses or bifocals,
prescription computer glasses with single vision lenses give you the additional
benefit of a much larger field of view for seeing your entire computer screen
clearly. (Keep in mind, though, that this type of computer eyewear is exclusively
for seeing objects within arm's length and cannot be worn for driving or other
distance vision needs.)
Also, a number of lens manufacturers have introduced special glare-reducing anti-
reflective coatings that also block blue light from both natural sunlight and digital
devices. You also may want to consider photochromic 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.
REFERENCE: INTERNET (https://www.allaboutvision.com)