# How many lumens/lux to cause permanent eye damage / blindness?



## Face (Sep 4, 2007)

Hi,

I was just wondering this last night after flashinging myself with a P3D Rebel 100 on Turbo. It left some spots in my eyes for a while but then, luckily, everything returned to normal.

But it made me think about roughly how many lumens/lux before you do yourself or someone else some permanent damage?

Cheers,

Face


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## Dinan (Sep 4, 2007)

Face said:


> Hi,
> 
> I was just wondering this last night after flashinging myself with a P3D Rebel 100 on Turbo. It left some spots in my eyes for a while but then, luckily, everything returned to normal.
> 
> ...



I don't think it's just the amount of lux/lumens that matters... a laser pointer with much less output than your P3D will cause permanent eye damage because the beam is so confined.


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## techwg (Sep 4, 2007)

I think the laser thing is about spectrum. If you are using radiation to propell a spectrum of light that contains IR then thats a bad thing for your eyes..


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## Ra (Sep 4, 2007)

Dificult to answer!!

The key word is surface-brightness..

With a few lumens, you can cause eye damage if the lumens come from a very small surface!

The source-surface of a laser is a few microns in size: Huge surface-brightness.

Ever looked directly at the sun on a clear day??: No torch (exept Maxablaster and lasers!) is capable of reaching the sun's surface-brightness.

It's not the amount of light, it's the concentration of light: The light of a ccfl never can be concentrated enough to cause eye damage. (low surface-brightness)
The light of a high surface-brightness source (xenon short-arc or mercury short-arc.. can be concentrated to a small, very intense spot in your eye, causing eye-damage. (if projected long enough at the same area)

You already noticed that the eye can endure high levels of light, but it has its limits! But during short exposure times, you don't need to worry about getting eye damage from the sun.. So you don't need to worry about the light comming from much lower surface-brightness-flashlights like yours.

How much surface-brightness actually causes damage depends on the exposuretime! So I cannot provide you with exact numbers.


So the best answer: Don't look into high-intensity light-sources if you're not forced to. (or for the fun of it.. )


Regards,

Ra.


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## mulotozink (Sep 4, 2007)

:sigh: i have a permanent spot i my vision from a laser


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## meuge (Sep 4, 2007)

Face said:


> Hi,
> 
> I was just wondering this last night after flashinging myself with a P3D Rebel 100 on Turbo. It left some spots in my eyes for a while but then, luckily, everything returned to normal.
> 
> ...


What matters isn't light per se, but the amount of energy delivered to the retina per unit area. 

If you can calculate the J/m^2 values for the eye at a given distance, you'll have a good guideline. 

However, further complication lies in the fact that before the light hits the retina, it will pass through the rest of the eye structures, which scatter/absorb/transmit different wavelengths differently. Because of that, the final amount of energy delivered to the retina will vary depending on the type of the light source. 

A coherent light source, such as a laser, will remain coherent while passing through the eye, and will thus deliver its energy very efficiently to the retina (not to mention the effects of positive interference of coherent waves)... which is why even a 5-10mW laser could cause eye damage. 

When a non-coherent beam strikes the eye, the different wavelengths not be transmitted the same way, thus dissipating the energy over the different tissue layers. 

The final layer of complication again has to do with the way different wavelengths interact with tissues, and the fact that shorter waves carry more energy.


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