Damage through eyelids?

Hi LPF,

Do you think that there is a handheld laser that could actually damage your eyes even with you eyes closed? My whole hand lighted up red when I shone 300mW 660nm on it, do you that maybe a 2W laser can actually damage your eyes while it's closed?:thinking: (Don't worry I'm not planning to do something stupid!)

Short answer: pretty safe with your eyes closed, if you can close them in time. But even with your eyes closed, a sustained direct hit can cause permanent damage.

The Sun, our closest star, is far enough away that it's light is practically parallel. And the strength of this light, at least on a mid-summer's day, is bloody concentrated and strong, per square centimeter. Most, if not all of us understand the dangers of staring into the Sun. The light, being parallel, enters the lens of our eye and focuses onto a tiny, tiny dot on the back of our eye (retina.)

The light receptors back there cannot handle this kind of concentrated light for very long. Maybe a second or two at the most. When we look away, we still see streaks of the Sun still on the back of our eye, that's because it takes a while for the rods and cones, now saturated, to recover.

If we continued staring at the Sun, it would cook those receptors lining our retina, and they would never recover nor work, again.

One of the most dangerous things about the properties of laser light, compared to other sources of light, is that the light is, more or less, parallel. Also, a laser <5mW is said to be as concentrated as the Sun, if not more. When a <5mW laser sweeps across our open eyes, it will cause the same kind of damage (be it permanent or temporary) to the backs of our eyes, in only a fraction of the time it takes the Sun.

Our brains aren't stupid. They can often tell when a light is too bright, and after many milliseconds, we respond by shutting our eyes.

Another problem with laser light, is it's single color, sometimes outside of the visible range, perhaps near visible, and in some cases, contain ultraviolet and infrared light. This light may not register in our brains as hurting or causing damage. Thus, in some cases, people are damaging their eyes and their brains don't even know it until it's too late.

Now, add the possibility that the laser may be several 1000s of mW, because as most of us know, 1000mW = 1W, and there are plenty of >1W lasers in the field. If this high power light even brushes across our eyes for a moment, our eyes don't even have a chance. Wherever that tiny spot focuses on our retina, is cooked for sure.

Now, let's say >2000mW of light hits our eyes, while they're closed. Light is still entering our eye. Thankfully, it is not parallel light focusing onto a tiny spot. It is broken up light. But it is still a great deal of light, and can saturate our receptors (rods and cones.) Given enough exposure time, I suspect even this kind of light can cause permanent damage.

Under the right circumstances, we can be blinded by strong laser light faster than your brain can close your eyes. Eye protection is a must.

Don't worry, I have appropriate goggles, I just wanted to know out of curiosity. Thanks for taking the time to write your short post! :thanks:

With a sufficiently powerful laser, the eyelid is simply not enough.

Take a decent flashlight, turn off the lights, and shine it at your eyes... you will see quite a bit of light.

A good flashlight is still blinding, even with eyes closed. I'm hesitant to imagine what the results would be with a 2W+ laser.

Doing so might result in a hole on your eyelid. :crackup:

The eyelid is an opaque membrane that will block most of the light even if it still looks bright. I highly doubt that any light that does not also damage the eyelids would case permanent blindness. Sure, temporary flash-blindness, but not permanent. I don't even think people who were "watching" nuclear blasts with eyes shut had eye damage, assuming they were far away enough to not suffer the heat damage.

http://laserpointerforums.com/f53/hit-eye-1000mw-445nm-blue-laser-69469.html

Damaged eyes?

I would Read each story in full...

I have no problem using my high power laser. It was bright for a few days then my eyes burned in and im good now







http://www.youtube.com/watch?v=a0AD5kJ6Wm0

^Again I'm going to say I am wearing safety goggles, I just wanted to know out of curiosity!

Cube777 said:

^Again I'm going to say I am wearing safety goggles, I just wanted to know out of curiosity!

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Like I said I don't have any problems using this laser. I have no problem looking at the beam or the dot at range. I only burn with the correct laser glasses equiped...

Plus it sucks being afraid of doing anything with your laser because you don't have proper eye protection. When I first built my 445nm laser it was a royal pain to just meter the damn thing with those crappy red goggles I had at the time; the red is a pain to see other stuff with and I wasn't sure if the protection was adequate. With better goggles it's much easier to see what you're doing while still being protected.

Bionic-Badger said:

Plus it sucks being afraid of doing anything with your laser because you don't have proper eye protection. When I first built my 445nm laser it was a royal pain to just meter the damn thing with those crappy red goggles I had at the time; the red is a pain to see other stuff with and I wasn't sure if the protection was adequate. With better goggles it's much easier to see what you're doing while still being protected.

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Im not afraid of this power laser anymore...

InfinitusEquitas said:

Take a decent flashlight, turn off the lights, and shine it at your eyes... you will see quite a bit of light.

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Anything that makes it past your eyelids isn't coherent. You'll burn your eyelids long before you burn your retina.

Cyparagon said:

Anything that makes it past your eyelids isn't coherent. You'll burn your eyelids long before you burn your retina.

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You're right... I was just pointing out that our eyelids are far from perfect in blocking light. Of course flash blindness is far from permanent damage, however it is still quite unpleasant, and serves to illustrate that it's best to be cautious.

HitShane said:

Im not afraid of this power laser anymore...

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I'd still be afraid of burning your eyelids. Not pleasant.

Imagine not being able to sleep because there are holes in your eyelids

Cube777 said:

Imagine not being able to sleep because there are holes in your eyelids

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Actually there are people that sleep with their eyes open.

Than there are also people who have lost their eyelids by accident.

You would eventually just adopt. The bigger problem to me would keeping the eyeball moist/lubricated. To deal with the light you can always just wear a blindfold.