Time and again I’m asked by patients how they can protect themselves against the damage caused by blue light as emitted by LEDs, be it from visual display units or “living room” lighting LEDs.
Well, what should we do here? Nothing, there is no danger!
In the Internet and the asocial media there are loads of “reports” and “advice” along these lines: LEDs have a strong blue emittance, and blue is known to cause eye damage (eye cancer!), thus you should avoid LEDs or use filters. I will not link to any of this. To top it, the fear thus evoked is being monetised and filters are offered for glasses or your monitors.
- Of course blue can harm, light in general, and blue more, because it has higher energy than red.
- But it depends on the intensity!
- Typical spectrum images, showing the “harmful” blue peak, are normalised to 100%.
- One simple measurement of mine found ≈5000 lx outside with a cloud-covered winter sky. A room-lighting LED spotlight, in contrast, illuminated with 120 lx in 2 m distance.
- In summer the illuminance outside could be 100,000 lx (Wikipedia).
- →The blue part emitted by LEDs is typically much weaker than the blue part of daylight. See animation above.
- Situations where light can cause sizable damage include:
- Directly staring into a strong (blue) theatrical flashlight
- Kids competing “who can look longest into a laser” – yes, a number of such cases are documented. It’s even worse with a laser beyond the allowed power level, which unfortunately can easily be ordered on-line. Etc.
I wrote the above a little simplified and with candour. But this isn’t just my “strong opinion”, there is good information available, here some examples.
- A BBC movie. Well explained, and also addresses the monetising aspects.
- In December 2019 there was a OSA webinar, where O’Hagan explained this in detail.
- O’Hagan et al. (2016) Low-energy light bulbs, computers, tablets and the blue light hazard. Clear statement here: “None of the sources assessed approached the exposure limits, even for extended viewing times.”
Sleep and circadian rhythm
With the claimed eye damage caused by LEDs, frequently the influence of blue on the sleep-wake cycle is intermixed. This, however, is a different and complicated issue that needs another blog entry. In brief: Only bright light bevor sleeping can be sub-optimal for your sleep, regardless of light source or colour. Just as common sense would tell you.