Stepping outdoors into sunlight, your eyes are being exposed to a variety of visible (and sometimes invisible) light rays that can have a range of effects. 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.

As we know, 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. Ultraviolet radiation, in moderation also has beneficial effects such as helping the body manufacture adequate amounts of vitamin D.

You may remember the blue-blocking sunglasses that were popular in the U.S. in the 1980s. The glasses, with their amber-colored lenses, had a bit of a cult following and were perhaps best known for how clear they made regular objects appear.

Here are important things you should know about blue light:

Blue light is everywhere.

HEV light rays make the sky look blue.

The eye is not very good at blocking blue light.

Blue light exposure may increase the risk of macular degeneration.

Blue light contributes to digital eye strain.

Sunlight is the main source of blue light, but now we have indoor, man made sources such as; flat screen TVs, LED lighting, display screens on computers, electronic notebooks, smart phones, ebooks and other digital devices, that emit significant amounts of blue light. Though the amount of HEV light these devices emit is a fraction of that emitted by the sun, it’s the amount of time, and proximity of the screen to the user, that's the issue. Many eye doctors and other health care professionals are concerned about the long-term effects of blue light on the eyes, and our health.

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. Blue light protection is even more important after cataract surgery, and one would benefit from eyeglasses with a special blue light filter.

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.

The AMA also pointed out that blue-rich LED streetlights operate at a wavelength that adversely suppresses melatonin at night — far more so even than other types of light. The AMA noted white LED lights "have a five times greater impact" on circadian sleep rhythms than conventional street lamps.

Risks noted by the AMA include risks to nighttime drivers, including:

• Worse nighttime glare than conventional lighting

• Discomfort & disability from these intense lights decrease visual acuity & safety

• Reduced sleep times

• Dissatisfaction with sleep quality

• Excessive sleepiness

• Impaired daytime functioning

• Obesity

Exposure to artificial light is one of the largest often-overlooked health risks of living in the 21st century. Your early ancestors had no such worries, as their day started and ended with the rise and fall of the sun, which synchronized perfectly with their circadian rhythm.

Your health depends on a regular light-dark cycle that, in a perfect world, starts and stops at the same time each day. By getting exposure to sunlight in the morning and at mid-day, you can protect the needs of your body's internal clock.

Examples of blue light filters for digital devices include:

Eyesafe (Health-E), iLLumiShield, RetinaShield (Tech Armor), Retina Armor (Tektide), Frabicon and Cyxus.

Apple Released Blue Light Filter In iOS Update For iPhones And iPads, and Night Shift feature on the Apple iOS 9.3 operating system, which activates blue light filtering at night.

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. You can also have a blue-blocking filter added to your prescription eye glasses.