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RANZCO outlines stance on blue light

A newly published RANZCO position paper has suggested there is little to no evidence blue light blocking spectacles improve visual performance or protect macular health, however screen-emitted blue light may interrupt circadian rhythms.

The college has released a six-page statement outlining its official opinion on the impact of blue light and digital screens on ocular health as part of its efforts to improve public awareness on the issue. The paper, approved by the RANZCO board in mid-2019 before being published online this month, addresses issues related to retinal protection, visual comfort and the impact on sleep.

It comes as Australia’s ophthalmic community works to clarify the benefits and myths surrounding blue light filters. Previously, Optometry Australia announced it is also reviewing literature in order to guide eyecare professionals in their recommendations.

According to RANZCO, no evidence exists to suggest normal environmental exposure, including that from digital screen technology, causes damage to eyesight and macular health. It also concluded filtering out blue light from screens is not necessary in normal use.

“Animal studies have generally used intensities and durations of light exposure that would rarely occur in normal life although some experimental evidence is emerging that repeated exposure at lower intensities may be more harmful than a single brief exposure,” the position statement said.

The paper cited a 2017 study by Moon et al that showed exposure of cultured retinal pigment epithelium cells to light equivalent to that emitted from mobile display devices caused free radical production and reduced cell viability.

“However, in life these cells are not directly exposed to blue light and extrapolation to real life exposure in humans may not be possible.”

In relation to devices, some authors have measured the blue light output to inform risk to the eye. “[And they] found that computer screens and smart phones have a very low level blue light radiance being about <0.5% of the luminance level that the International Commission on Non-Ionizing Radiation Protection consider safe.”

Sleeping patterns

According to RANZCO, it has become increasingly apparent that screen-emitted blue light can have an effect on circadian rhythms. This is due to specific cells in the retina that respond best to blue light, contributing to signals that control the biological clock.

“Blue light is beneficial during daylight hours because it boosts attention, reaction times, and mood but is disruptive at night,” the paper said.

“Melatonin is a neurohormone that regulates sleep. Experiments comparing the effects of exposure to blue light with exposure to green light show that blue light suppresses melatonin for about twice as long as the green light and shifts circadian rhythms by twice as much (3 hours vs. 1.5 hours).

“Studies have also shown that blue light in the range of 470–490 nm is more effective compared to monochromatic light of 555 nm in phase-shifting the human circadian clock.”

The college recommended there maybe benefits to reducing screen time in the evening or using night-time screen settings a few hours before bedtime.

With regards to reducing the symptoms of eyestrain, patients should take regular breaks, occasionally focus on distant objects and ensure spectacles, if worn, are appropriate for the task.

The merits and disadvantages of blue light blocking IOLs was beyond the scope of this position paper but may form part of future statements. RANZCO will undertake its next blue light review in July 2022.