Prolonged device use has harmful side effects, just not in the way some interpreted.

Blue light hastens vision loss? ‘Not so fast,’ doctors say

'Blue light accelerates blindness,' headlines declare following new research, but doctors warn that reports of digital screen-time-induced vision loss are greatly exaggerated.

"As far as I can tell, there is no cumulative effect for such low energies."


Published in the open-access journal Scientific Reports, the study found intense blue light exposure triggered retinal-generated molecular toxicity that destroyed photoreceptor cells in a similar way to age-related macular degeneration (AMD). But that's not the whole story, and now doctors hope to set the record straight.

Blue light, high-energy wavelengths of light between 420 and 480 nm on the visible light spectrum, naturally suppresses the body's melatonin production, boosting alertness and attention; however, after sundown, this effect can disrupt the body's circadian rhythm. That's why the advent of high-energy artificial lighting and digital screens has drawn scrutiny and even the implication that it could do more harm than good.

Hence, blue light exposure remains an open-ended clinical question that chemists at The University of Toledo (UT) sought to address. Per their study, researchers examined how blue-light-excited retinal (vitamin A aldehyde) triggered cytotoxicity in the retina, killing the photoreceptor cells that signal the brain. Once those photoreceptor cells die, they cannot regenerate much in the same way as AMD.

To study this interaction, researchers introduced retinal molecules to other cell types in the body-cancer cells, heart cells and neurons-and when exposed to blue light, the cells died because of the combination with retinal, a university press release notes. Interestingly enough, blue light alone or retinal without blue light exposure had no cellular effect.

"No activity is sparked with green, yellow or red light," notes Ajith Karunarathne, Ph.D., assistant professor in the UT Department of Chemistry and Biochemistry. "The retinal-generated toxicity by blue light is universal. It can kill any cell type."

Additionally, researchers found that a molecule named alpha tocoferol, a vitamin E derivative and natural antioxidant, can help prevent the cells from dying. However, as people age or their immune system is suppressed, they lose this ability to fight against blue light.

That being the case, researchers note these interactions were not observed in living eye tissue but in cellular proxies in a laboratory setting as opposed to an actual human eye. What's more, the observed changes appeared only at microwatts (µW) of intensity above a typical threshold for digital devices, says Karl Citek, O.D., Ph.D., AOA Commission on Ophthalmic Standards member and subcommittee chair for the American National Standards Institute (ANSI), which sets consumer-protection standards for the manufacture of sunglasses and over-the-counter readers.

"Researchers showed an effect at the given wavelength (445 nm) only when the energy was at 4.86 microwatts or greater," Dr. Citek notes. "Previous research has shown that effects only occur when the energy is 3 µW or greater. Electronic devices typically emit no greater than 1 µW, and as far as I can tell, there is no cumulative effect for such low energies."

Blue light: The Verdict

If anything, Dr. Citek says the study lends support for the importance of wearing UV-A and UV-B blocking sunglasses outdoors in sunshine. As compared to digital screens, sunlight's intensity is vastly greater. As such, unprotected eyes exposed to excessive amounts of UV radiation in only a short amount of time can develop painful sunburn on the eyes, known as photokeratitis. However, long-term overexposure to UV radiation over the course of one's life can cause more serious problems, such as AMD, cataract, pterygium, or even increased risk for some forms of cancer.

Research categorically shows overexposure to UV radiation can increase the risk for serious sight-threatening conditions, but the verdict is out on blue light emitted from digital screens. That said, blue light's effect on circadian rhythm at night is documented, and it's recommended that people avoid bright screens up to 2-3 hours before bedtime and use dim or reddish lighting at night.

Click here to read how nutrition could play a role in blue light exposure.

August 21, 2018

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