Disclosures: Teran reports he is a consultant to Seto. Please see the full study for all other authors’ relevant financial disclosures.
June 24, 2020
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Smartphone ‘night mode’ superior to blue light-blocking spectacles

Disclosures: Teran reports he is a consultant to Seto. Please see the full study for all other authors’ relevant financial disclosures.
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Activation of night mode functions on smartphones more efficiently reduced the amount of short-wavelength light compared with commercially available blue light-reducing spectacle lenses in a study focused on digital devices and their potential effects on circadian cycles.

“Exposure during the evening to short-wavelength (blue) light produced by the screen of smartphones could have deleterious effects on human health through the alteration of the circadian rhythm,” Emiliano Teran, PhD, from the Autonomous University of Sinaloa in Mexico, and colleagues wrote. “This negatively impacts sleep quality and duration, which in turn has widespread effects on human health, including increased mortality risk, weight gain and obesity, diabetes risk, cardiovascular disease, neurocognitive function, mental health and traumatic accidents (such as car accidents).”

Teran and colleagues compared the melatonin suppression values found after use of night mode functions on digital devices with either LCD or active-matrix organic light-emitting diode (AMOLED) screens and values found after use of four blue-light filtering spectacles.

They found that while high-end smartphones had the brightest displays, which could produce an increase in melatonin suppression value (MSV) of approximately 17% to 30%, installed applications that selectively reduced the amount of blue light decreased this effect by up to 90%.

In contrast, coated lenses reduced the MSV by 21% to 35% compared with using no lens. For tinted lenses it was between 12% to 15%. Uncoated control spectacle lenses reduced the MSV by 13% to 14%, as reference.

“As expected, the warmer the night mode function, the more efficient it was in reducing the circadian illuminance produced by smartphone screens,” Teran and colleagues wrote. “However, night mode is only effective if the device has a night mode function, the user actively turns the night mode function on (ie, not a default setting) and the night mode function in a display does not reduce short-wavelength light from other environmental sources such as room lighting.”

The researchers concluded that although the lenses had a lower effect on MSV, the combination of both spectacles and night mode functions could further reduce exposure to blue light and may be the optimal approach.