Research published last fall found that LED light causes irreparable harm to retinal pigment epithelial cells in vitro.
You will be seeing a lot of ink about this story, first reported by UPI. Six vision researchers from Madrid, Spain published a study in the journal Photochemistry and Photobiology (Volume 89, Issue 2, pages 468-473, March/April 2013). It appeared online last October, but not for free.
The researchers exposed human retinal pigment epithelial cells, in Petrie dishes, to light from LEDs for three light-dark cycles of 24 hours each (12 on, 12 off). The LEDs emitted white, blue (468 nm), green (525 nm), and red (616 nm) light. After 72 hours they checked for cellular viability and several specific kinds of cell damage. Long story short: The cells exposed to all frequencies of LED-produced light were less viable and exhibited damage. The researchers summarize the situation in the abstract: "LED radiations decrease 75-99% cellular viability, and increase 66-89% cellular apoptosis [cell death]. They also increase ROS [reactive oxygen species] production and DNA damage."
The abstract of the paper is available online, but the full paper requires a paid subscription or purchase, so I have not seen the details of this research. I wondered about a number of points not spelled out in the abstract: the spectrum of the white-light LED, the intensity of the light in all four colors, and the reliability of the markers used to ascertain cell damage.
One of the researchers, Celia Sanchez Ramos from Madrid's Complutense University, told UPI:
Eyes are not designed to look directly at light -- they are designed to see with light. This problem is going to get worse, because humans are living longer and children are using electronic devices from a young age, particularly for schoolwork, instead of paper.
Displays vs. lighting
If the problems reported by these researchers are real, and are caused by LED light directly striking the retina, then most LED lighting applications are off the hook -- people perceive their light after reflection, absorption, and re-emission. It's more about LEDs used in displays and signage, particularly computer displays at which people are apt to stare for hours at a time. The researchers don't have any easy answers; Sanchez-Ramos suggests wearing good-quality, UV-filtering sunglasses and eating a diet rich in vitamin A. The shades won't help much if white and blue LED light are causing retinal damage, however.
This research overlaps with the concerns of scotobiology, which we wrote about earlier this month. At this week's live chat on Thursday, May 16, our guest will be scotobiologist Robert Dick, and the research sketched here is certain to come up in the conversation. Hope you can join us for this chat at 1:00 p.m. ET (10:00 a.m. PT).
— Keith Dawson , Editor-in-Chief, All LED Lighting