E-Ink announced today (March 13) the results of a peer-reviewed study by the Harvard School of Public Health on the effects of displays on cells in the user's retina. The study found that brighter, bluer (or cooler) light creates more stress on retinal cells.
According to Nielsen , the average adult spends about 13 hours a day in front of a screen. That screen time also comes at a price: the high-energy blue light emitted by standard liquid crystal displays (LCD) and LED screens can be potentially harmful when stared at for extended periods of time. Blue light poses a threat to the retinal cells of the eye, disrupting the biological clock and restorative sleep. Key conclusions of the Harvard study include:
- The light spectrum generated by the display is one of the main factors that stress the cells of the retina.
- Devices including E Ink's ComfortGaze™ headlight can have up to three times less impact on retinal cells than LCD devices .
- Color temperature regulation can affect the level of stress response of retinal cells, but LCDs are less effective at regulating day and night patterns than lighting solutions that use a spectrum designed for eye safety .
- E Ink devices without a front light don't produce any blue light to stress the retinal cells.
The study compared two different types of displays: liquid crystal displays (LCDs) and e-ink displays with front lights. There is a key difference between the lighting function of liquid crystal and electronic ink. In order to see an image on an LCD display, a backlight based on LED technology is usually used to transmit light through the liquid crystal material. In contrast, E Ink's e-ink displays are like a sheet of paper: They don't emit any light, but instead reflect ambient light to illuminate the screen. In dim or dark situations, when there isn't enough light for reading, E Ink displays use a front light to act as a built-in light.
For this study, ePaper devices were tested with different types of headlights: cool white, warm yellow, and with the new E Ink ComfortGaze™ headlight. ComfortGaze™ is engineered to reduce the amount of blue light reflected off the screen surface, providing a more comfortable reading experience and keeping the light output from having an amber tint.
Studies have found that E Ink ComfortGaze™ reduces harmful blue light output without producing an amber-ish white spectrum in night light mode. Devices using ComfortGaze™ can use warm white mode for three times as long as the LCD in cool white mode and twice as long as the same LCD in warm white mode to achieve the same level of retinal cell stress.
E-ink displays without front lights have advantages even over printed paper. Bright white paper contains optical brighteners that are not present in E Ink displays. These brighteners produce not only the clean bright white of printed paper, but also increase blue light reflection. In other words, E Ink displays can be considered safer than printed paper.