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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.

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.

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 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.

But ultra­vi­o­let radi­a­tion, in mod­er­a­tion, also has ben­e­fi­cial effects, such as help­ing the body man­u­fac­ture ade­quate amounts of vit­a­min D.

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:

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 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.

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 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 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.

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 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 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.

Exam­ples of blue light fil­ters for dig­i­tal devices include: Eye­safe (Health-E), iLLu­miShield, Reti­naShield (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 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 bifo­cals or pro­gres­sive lens­es, pre­scrip­tion com­put­er glass­es 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.

Ask your eye doc­tor about 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.



June 15th, 2017|Comments Off on Blue Light: It’s Both Bad And Good For You

About the Author:

Born in Connecticut and raised in Upstate New York , Dr. Stetson graduated Cum Laude from Colgate University in New York, and then earned an MD degree with honors at the University of Vermont College of Medicine. He distinguished himself again in residency at the Albany Medical Center, where he obtained the highest percentile in the Ophthalmology Knowledge Assessment Examinations. Dr. Stetson has performed more than 50,000 refractive surgeries and has been on staff at Diamond Vision since 2004, before becoming Medical Director in 2006.


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