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Optometrists question blue light study

31/10/2018By Richard Chiu • Staff Journalist
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The true impact digital blue light exposure has on vision is still up for debate optometry experts have said, despite a recent study claiming it can accelerate blindness.

American National Standards Institute subcommittee chair Dr Karl Citek, who is also a member of the American Optometric Association (AOA) Commission on Ophthalmic Standards, warned in an article published in the AOA online news portal that reports of digital screen-time induced vision loss are greatly exaggerated.

“Researchers showed an effect at the given wavelength (445 nm) only when the energy was at 4.86 microwatts (μW) or greater,” Citek said.

“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.”

Citek said tests in the study were carried out on cellular proxies in a laboratory as opposed to observing the reactions on living tissues, such as the actual human eye. Also, the observed changes appeared only at microwatts of intensity above a typical threshold for digital devices.

Chemists at The University of Toledo (UT) 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.

The 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, according to the press release from the university. However, blue light alone or retinal without blue light exposure had no cellular effect.

“No activity is sparked with green, yellow or red light,” Assistant Professor Ajith Karunarathne from the UT’s Department of Chemistry and Biochemistry said.

“The retinal-generated toxicity by blue light is universal. It can kill any cell type.”

The researchers also found that a molecule called 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, the ability to fight against blue light gets lost.

Blue light is high-energy wavelengths of light between 420–480 nm on the visible light spectrum, which naturally suppresses the body’s melatonin production, boosting alertness and attention. But after sundown, the effect can disrupt the body’s circadian rhythm.

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Despite questioning the study’s results, Citek stressed it still highlighted the importance of wearing UV-A and UV-B blocking sunglasses outdoors. As compared to digital screens, the sunlight’s intensity is much greater and 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.

Long-term overexposure to UV radiation can cause more serious problems, including AMD, cataract, pterygium, or even increase the risk for some forms of cancer, Citek added.

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