# Can a 40 or 50 lumens LED cellphone flashlight damage retinas?



## LynniieRockz (Dec 17, 2011)

Hi.. I've been shining my flashlight onto my eyes when putting my eye drops at night, .I've been doing this for months  I had no clue it could burn my retinas. I don't think I can see any differences in my vision but I can't find any where the exact symptoms of retinal burns.. So can a 40 or so lumens flashlight cause any damage? If anyone here has burn their retinas can you tell me what are the signs of a burned retina? THANKS IN ADVANCE


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## Th232 (Dec 17, 2011)

I don't think so, but I really think you should ask an optometrist or opthalmologist about the burnt retina bit rather than some people on an internet forum. I did find some interesting links by googling "burnt retina symptoms" though.

Hope there's nothing wrong with your eyes...


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## Mr Happy (Dec 17, 2011)

LynniieRockz said:


> Hi.. I've been shining my flashlight onto my eyes when putting my eye drops at night, .I've been doing this for months  I had no clue it could burn my retinas. I don't think I can see any differences in my vision but I can't find any where the exact symptoms of retinal burns.. So can a 40 or so lumens flashlight cause any damage? If anyone here has burn their retinas can you tell me what are the signs of a burned retina? THANKS IN ADVANCE



It's not about the lumens, it's about the light intensity. Think for a moment, some lasers have no lumens to speak of yet they can damage your eyes instantly.

If a light seems bright enough to make you squint, or leaves spots in front of your eyes afterwards, it is too bright. Don't look into such a light.

If you are worried, you should go consult a specialist. And don't stare into bright lights!


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## yifu (Dec 18, 2011)

Mr Happy said:


> It's not about the lumens, it's about the light intensity. Think for a moment, some lasers have no lumens to speak of yet they can damage your eyes instantly.
> 
> If a light seems bright enough to make you squint, or leaves spots in front of your eyes afterwards, it is too bright. Don't look into such a light.
> 
> If you are worried, you should go consult a specialist. And don't stare into bright lights!


Lasers are actually the most efficient light source mankind has, laboratory lasers have efficiencies exceeding 300 lumens per watt, twice the efficiency of the XML LED. Even those 1w/2W pen lasers have significant lumen output, even though the light is monochromatic and by definition have almost 0 CRI. It is the lux, not the lumens that causes damage, and high output especially in the UV/infrared range can cause burns more readily. Considering the sun at mid-day is 100 000 lux and an office lighting fixture is usually 1200 lumens/200 lux, i don't see how it is possible that a 40 lumen light can cause permanent eye damage, unless it's focused with an aspheric lens or something.


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## Helmut.G (Dec 18, 2011)

Hey LynnieRockz,

don't worry too much. I would say it's unlikely that your eyes are damaged.

If you are really worried, see a doctor.

If you really want some good help from CPF you need to describe what you did and what kind of light you used in a much more detailed manner.


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## Kitchen Panda (Dec 18, 2011)

LynniieRockz said:


> Hi.. I've been shining my flashlight onto my eyes when putting my eye drops at night, .I've been doing this for months  I had no clue it could burn my retinas. I don't think I can see any differences in my vision but I can't find any where the exact symptoms of retinal burns.. So can a 40 or so lumens flashlight cause any damage? If anyone here has burn their retinas can you tell me what are the signs of a burned retina? THANKS IN ADVANCE



As I read on another thread around here somewhere, an ophthalmologist will use a slit lamp with several hundred lumens to examine your retinas. I suspect "prudent avoidance" is all you need to do here; if the light is bright enough to make you squint or blink, maybe you shouldn't stare at it for a long time. As long as the eye's built-in defenses are working, I wouldn't lose sleep over incidental exposure. Though I admire your dexterity in handling both the cell phone and eye drops at the same time - I have to hold my eyelid open with one hand, drops in the other, leaving no hands available for light manipulation. Room light has always done the trick for me. 

Bill


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## Mr Happy (Dec 18, 2011)

All super bright LEDs come with a warning not to stare into the emitter. A modern white LED may have a light intensity greater than the surface of the sun when looking directly into the lens. They are unquestionably dangerous and you should definitely not shine them into your eyes. Remember the lens of your eye will focus a point source into a point on your retina.


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## LE6920 (Dec 21, 2011)

Never seek or put too much stock in medical advice obtained on the iternet!


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## Cataract (Dec 22, 2011)

My collection of facts on the subject:

I went through an eye examination myself where the doctor put drops in my eyes to dilate my pupils and he then shone a light right into my eyes. It was completely blinding; I couldn't see anything other than a torturingly bright white light that made me wet my whole face with tears and the exam lasted for a few minutes per eye. They then told me it is possible I might need some special one-time use sunglasses to drive. I came back in to ask them for the glasses as I couldn't bear the sunlight even in the car. No damage came out of it and it is a standard procedure.

I've flashed myself with WAY more than 50 lumens many many times and I can't say I have any side effects.

Someone on here once asked an ophtalmologist about eye damage with a flashlight and the response was something like "I'd be very surprised a flashlight could cause any eye damage"


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