Knowledge Center

Light, what allows us to see, is much more complicated than what you might know.

All sources of light, from the sun to our phones, flashlights and headlights work by exposing our eyes to a variety of visible and invisible energy. What we see is called the Visible Light Spectrum. We will spare you most of the physics lessons, but a little is necessary. Visible light is composed of energy with wavelengths from roughly 380 – 700 nanometers.

Energy with shorter wavelengths are called Ultra-Violet (UV) and energy with longer wavelengths are known as Infra-Red (IR).

What Is Blue Light?

As we said, visible light is a large spectrum ranging from 380 – 700 nanometers. Blue light is a subsection of this ranging from 380 – 500 nanometers. This is the shortest wavelength of visible light, but has the highest energy levels. This is why Blue Light is sometimes referred to as “High Energy Visible” or HEV light.

Key Points About HEV

Like all energy, including UV, IR and Visible Light radiation, visible HEV — the portion of the visible light spectrum with the shortest wavelengths and highest energy — has both benefits and dangers.

Blue light is everywhere.

Sunlight is the main source of HEV, 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 HEV, 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 HEV. 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 HEV on eye health.

The eye is not very good at blocking HEV.

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. On the other hand, virtually all visible HEV passes through the cornea and lens and reaches the retina. Blue Light filters such as our unique Blue Blockers help keep the HEV from even getting to the eye.

What is so good about HEV?

HEV has many positive effects on the human body. It helps regulate the circadian rhythm. It slows the release of melatonin, therefore boosting alertness. It helps with memory and cognitive function as well as elevating mood. In fact many people with Seasonal Affective Disorder and other similar conditions, obtain relief with Light Therapy utilizing extra HEV exposure.

But too much of a GOOD thing can be BAD.

The amount of natural HEV we would get from spending 3 - 6 hours per day outside in the sunlight is probably optimal. Factor in the different quality from artificial sources (more on this later) as well as the increased exposure in our digital world and we can start to see negative effects.

Many people, especially children, spend significant amount of time looking at phones, tablets or watching LED TV’s before bed. At this time in the evening, the body’s circadian rhythm should be preparing itself for sleep. It starts to release extra melatonin, a natural relaxing/sleep hormone. Reduced melatonin production secondary HEV exposure is a significant factor in difficulty sleeping, or getting a restful night’s sleep. If you ever wonder why your kids are having trouble sleeping at night, consider the timing and amount of digital device time they get.

Poor quality and quantity of sleep also brings with it day time fatigue, increased risk of obesity, diabetes, heart disease and depression.

Additionally there is ongoing research about the effects of nighttime HEV exposure and certain types of cancers.

So why are digital devices so bad?

In addition to the timing and increased exposure already discussed, the quality of HEV is different between natural and artificial sources. Natural sunlight has it’s energy distributed rather evenly over the full range of visible light. Thomas Edison’s good old incandescent lightbulb is somewhat similar in it’s energy distribution to sunlight. LED lights from TV’s, phones, tablets, computers and compact fluorescent lightbulbs on the other hand are more vivid due to their uneven distribution. They tend to peak in certain areas with their largest peak around the 430 – 455 nanometer wavelength. This uneven distribution is unnatural to the human body and tends to highlight the bad properties of HEV, while minimizing the good.

How does all this affect my eyes?

HEV (as well as UV energy), being of higher energy, can be particularly damaging to the vital macular photoreceptors. As we stated earlier, much of the UV is blocked by the front structures of the eye. In addition, even clear eyeglass lenses block almost all UV from even getting to the eye. Even with this reduced penetration, we know that UV exposure is the 2nd strongest risk factor for Age Related Macular Degeneration (ARMD), behind only smoking. With the relatively short time that we have seen a proliferation of LED lights, it is too early to see the natural course on our eyes, however the potential to see a dramatic increase in the incidence and severity of ARMD certainly exists. Early laboratory studies are proving this to be true.

In fact, studies are showing that the most damaging wavelength of light to the retina, centers just around 445 nanometers, which if you recall is the greatest peak in wavelength of LED devices. Our Blue Blockers lenses filter this specific wavelength.

Although more research is needed to determine how much natural and man-made HEV is "too much blue light" for the retina, many eye care providers are concerned that the added HEV exposure from computer screens, smartphones and other digital devices might increase a person's risk of macular degeneration later in life.

Blue light also 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 nanometers increase contrast significantly. Our Blue Blockers can easily reduce this strain and increase contrast.

So what can be done to protect yourself

Reducing your amount of exposure to HEV emitting sources is certainly the key to help protect yourself from the harmful effects. Especially important are the artificial sources discussed. This can be achieved in a number of ways.

Reduced screen time: Easy in concept but not always in reality. A good recommendation on the amount of screen time is around 2 hours a day at a maximum. Furthermore, it is advisable to break that up to no more than 30 minutes at a time. This can significantly increase your contrast and reduce eyestrain and the potential damaging affects to the retina. In addition, avoid exposure in the few hours before bedtime for improved sleep patterns.

Physical device filters: A number of manufacturers make filters that attach directly to your devices. These filter out the harmful HEV, while allowing other light to pass to your eyes. In addition to protecting your eyes, they can also protect your screen from scratches and other damage.

Software filters: For smartphones and tablets, there are a number of apps that will filter out the more intense HEV. These serve not only to protect your eyes, but also increase contrast and help lessen the negative effects on Circadian rhythm.

Eyeglass lenses: HEV filters are becoming increasing common on eyeglass lenses. Applied as a coating much the same way as Anti-Reflective or UV coatings are, these lenses will then filter out the excessive HEV, helping to reduce the negative impacts from increased exposure. These can be used as single vision lenses or in progressive lenses. Lenses with no prescription, but with a HEV filter are even commonly worn by people who either do not need a prescription or to be worn over contacts. At Payne Glasses, we make protecting yourself from damaging HEV a very affordable option with our unique Blue Blocker technology.

In Summary

From the beginning of human history, we have always been exposed to HEV. Over the past decade, advancements in technology have had a tremendous impact on our daily lives. Daily tasks are easier and we are able to work more efficiently, however there are some negative consequences of this technology. One of these is the increased exposure to HEV. With that can come sleep problems, obesity, depression, vascular disease and certainly increased risk of ocular problems, most significantly ARMD. Following the simple guidelines above, complete with Blue Blocker lenses from Payne Glasses, can have both an immediate and long lasting impact in quality of life for many people.