Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: AndroidNeox on 27/05/2013 20:27:08
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I've read that LED's produce light with a "blue glare" that can permanently damage the retina. Is this true? If so, what might we do to protect ourselves?
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LEDs are certainly capable of producing radiation intensities that can harm sight. Laser LEDs are a good example! A friend at medical school dismantled an old laser printer to find out how it worked; activating the laser source he though nothing was coming out so he looked at it... the black blob on his macula took a while to disappear...
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Devices containing lasers must be labelled with a warning label - devices used around the home are usually "Laser Class 1", which means that they are eye-safe, in the sense that the light is bright enough to make you blink, but not so powerful that it will permanently damage your eyesight before you can blink. Classes 2 & above require additional protection like automatic shutdown or mechanical shutters to block the dangerous light intensity.
There are now ultraviolet LEDs (https://en.wikipedia.org/wiki/Light-emitting_diode#Ultraviolet_and_blue_LEDs) which also produce some energy at the visible blue/violet end of the spectrum (perhaps the "blue glare" mentioned in the question). When exposed to ultraviolet or infra-red light, your eyes do not detect the damaging intensity (because it is invisible), and so you may allow yourself to be exposed for a long period.
Most ultraviolet is absorbed by the lens of the eye, and does not reach the retina. However, extended exposure to Ultraviolet light can produce cataracts and skin cancer.
Intense Infra-red can damage the cornea and burn spots in your retina; because the retina does not have heat sensors, you don't feel the damage as it is happening.
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Thanks, Evan; that is indeed what happened to my medical school laser printer-dismantling friend. He looked at the IR laser source and thermally stressed a few photoreceptors...
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I've read that LED's produce light with a "blue glare" that can permanently damage the retina. Is this true? If so, what might we do to protect ourselves?
"White" LEDs normally comprise an actual blue LED coated with a white phosphor. The spectral output typically has a pronounced blue peak (and you may get more dominantly blue regions at the edges of the beam if the phosphor coating isn't uniform.
See https://en.wikipedia.org/wiki/File:White_LED.png (https://en.wikipedia.org/wiki/File:White_LED.png)
I think it unlikely that this residual blue would cause any lasting damage in practice (unless they were extremely poor quality LEDs with terrible phosphor coverage).
Fully fledged high power blue LEDs (1 to 3watts or more) will cause after-images on the retina if looked at for a few seconds - and this isn't recommended!
The hazard with deep blue LEDs is that the eye isn't very optically responsive to blue, so the damage potential can be much greater than it looks.
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This retinal damage from LEDs was reported on BBC (this past week, I think), but I didn't get the science details.