Blue Light: Your Eyes on Screens?>

Blue Light: Your Eyes on Screens

by UCB Health & Wellness Publications  

Laptops, tablets, and smartphones have transformed our lives, dramatically changing the way many of us spend our time. So it’s no wonder researchers are investigating whether staring at glowing screens for hours at a time may have unwanted side effects.

In the field of vision care, one concern focuses on blue light, the spectrum emitted by digital screens of all kinds. And screens aren’t the only source. New lighting technologies such as compact fluorescent lights and light-emitting diodes, or LEDs, also produce light predominantly in the blue spectrum. Perhaps never before have people been exposed to so much light in the blue spectrum for so many hours of the day and night. Could exposure to all of these sources of blue light be damaging our eyes? Does it cause age-related macular degeneration (AMD)?

Even before researchers have had time to answer any of the questions, manufacturers have rushed in, marketing a variety of blue light–filtering gadgets. Slick websites have popped up, issuing dire warnings about the hazards of blue light—and, naturally, offering all kinds of products to help protect against it, from special lenses to vitamin supplements. Should you consider buying lenses that protect your eyes from blue light, especially if you already have AMD?

Here’s what researchers know—and don’t yet know—about the risks.

Unproven dangers

Bright light of any kind, especially sunlight, can damage our eyes. Ultraviolet (UV) radiation, which is not visible, has been linked to the formation of cataracts and damage to the cornea. (It’s also the chief culprit in skin cancer.) UV light is mostly absorbed by the eye before it reaches the retina. But visible light does reach the retina—it’s how we see, after all.

Visible light consists of a wide spectrum of wavelengths, represented by all the colors we see. Some research suggests that visible light from the blue spectrum may be especially damaging to the eyes. That has led some experts to speculate that prolonged exposure to blue light, over a life span, could be a factor in the development of AMD.

But even with the proliferation of glowing screens and LEDs, most of our exposure to blue light comes in the form of good old sunlight (followed by fluorescent light, compact fluorescent light bulbs, and LED light). Blue light from screens may add to the risk of damage, but so far the evidence is based mostly on animal studies and remains theoretical for humans. Researchers have yet to definitively link exposure to blue light from artificial sources to an increased risk of AMD, or any other eye diseases. For that reason, many ophthalmologists think that it is premature to invest in lenses that filter out blue light. Wearing UV-protective sunglasses when you are outside remains the most important way to protect your eyes from damage.

The circadian connection

There’s another reason to be cautious about choosing blue light–filtering lenses. Scientists have learned in recent years that light in the blue spectrum plays a crucial role in regulating our circadian rhythm—the internal clock that determines waking, sleeping, and a host of physiological processes. In the morning, blue spectrum light, mostly from sunlight, wakes us up and stimulates the body. Wearing eyeglasses or contact lenses that block blue light could disrupt the normal circadian rhythm, potentially making people sluggish and less alert in the morning.

Whether this concern is warranted or not remains to be seen. In a study published in the journal PLOS One in January 2017, researchers tested five different blue light–filtering spectacles. The lenses worked as advertised: They blocked a modest proportion of blue light. In theory, that might help protect against damage to the eye. But the lenses also blocked out enough blue light to potentially affect color sensitivity and interfere with people’s circadian rhythm, the researchers found. Even that wasn’t certain, however. When the researchers tested the lenses in a group of 80 subjects, they found that more than 70 percent of the volunteers could not detect any impairment in vision or sleep quality.

For now, based on current evidence, the American Academy of Ophthalmology does not recommend the use of blue light–filtering lenses—or the use of any kind of special glasses for computer work.

What about light boxes?

Recently, another electronic device has raised new concerns: natural-spectrum light boxes. The light generated by light boxes is meant to simulate sunlight, with the full spectrum of visible light. Light boxes are typically recommended to ease seasonal affective disorder (SAD), a form of depression that is linked to low levels of sun exposure during the winter months. Light boxes are now available over the counter, but they are not approved or regulated by the FDA. And while they generate only a fraction of the intensity of sunlight, there’s worry that exposure for too long, especially over time, might cause damage to eyes.

So far, though, no studies have definitively linked light boxes to retinal or corneal damage. Still, it is wise to play it safe. If you already have vision problems such as AMD or cataracts, speak with your ophthalmologist before using any kind of light box.

Bottom line

Researchers still have a lot to learn about the effects of the artificial light we’re increasingly exposed to from digital screens and other sources. And even if blue light from your mobile phone or tablet poses no risk to your eyes, there are still reasons you may want to limit screen time, especially in the hours before bedtime. Blue light from the sun normally helps to awaken us and reset our circadian rhythm. Preliminary studies suggest that exposure to blue light at night may disrupt that rhythm and make it more difficult to fall asleep.

Staring for too long at glowing screens can also lead to headaches, eye strain, blurred vision, or dry eyes—symptoms that are collectively referred to by eye-care specialists as computer vision syndrome or digital eyestrain. Staring at your smartphone or tablet for long stretches of time may be different from, say, reading a book or newspaper because people tend to blink less when they are looking at a digital screen.

If you must use a computer or tablet and can’t limit screen time, you can limit blue light exposure and eyestrain by turning down the brightness setting on your device in the evening. Some new devices have a “night shift” feature that you can turn on to reduce the amount of blue light the screen produces. And it’s always worth following the 20-20-20 rule. Every 20 minutes, look up from your screen and focus on an object at least 20 feet away for at least 20 seconds. If your eyes feel dry, try blinking more often or using artificial tears to moisten them.

This article first appeared in the 2019 UC Berkeley Vision White Paper.