# Led Monitor damaged my eyes



## assassin966 (Apr 25, 2012)

I was using pc for over 10 years never had any problems before but now after buying an LED monitor it started to damage my eyes i have notice after buying samsung px2370 using it for like 2 months now i have my eyes damaged and never had tham before i have buyed LED monitor becouse i heard that it has better picture quality and its better for eyes but now after using LED monitor i have notice that its damaging my eyes please tell me how is this possible or im allergic to LED back light i have been no more using pc more than 6-7 hours per day and it damaged my eyes !


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## Lynx_Arc (Apr 25, 2012)

Are you sure your eyes are damaged or just strained? Most likely you went from a lower resolution tube monitor to a higher resolution LCD display (with LED backlighting). Smaller crisper fonts can cause your eyes to strain and if you still have a tube type tv set going from watching an LCD to tube type display can further stress your eyes.


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## dc38 (Apr 25, 2012)

Hey Assassin, welcome to CPF. Led's and lcd's should actually cause less strain on your eyes...Also, there's your problem in your post...you use the computer for 7 HOURS A DAY. That usually leads you to strain your eyes when looking elsewhere because you're situated around 1-2 feet away from the screen. Since that's all you stare at for 7 hours, your eyes have to work a little harder to focus on further things. (recommended usage is 1-2 hours at a time with a 30-60 minute break in between sessions. CRT's (box monitors) actually are more harmful and cause more eye strain because they do not have a flat viewing surface. Not only that, but the viewing angle of CRT's are weird. Your eye level should be near the top of the screen, with you looking slightly angled down. With LCD's, your eyes should be at 2/3 to 3/4 the height of the screen for optimal viewing. Also, maybe the strain from your previous extended usage of CRT monitors is finally catching up to you.


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## 127.0.0.1 (Apr 25, 2012)

define damage. it this damage determined by eye exam and testing ?

regular old eyestrain can manifest itself by double-vision when going out into sunlight

_*avoid blue color schemes and backgrounds on monitors*_, blue can cause the most eyestrain


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## znomit (Apr 25, 2012)

Explain "damage".
Swapping from a small CRT to a huge LED might mean you are getting more heat off the screen drying your eyes out.


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## mattp (Apr 25, 2012)

znomit said:


> Explain "damage".
> Swapping from a small CRT to a huge LED might mean you are getting more heat off the screen drying your eyes out.



Ahhh, that'll be the problem, he's sitting waaaay too close. 

But seriously, I can't see how you can 'damage' your eyes physically by looking at a screen.


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## alpg88 (Apr 25, 2012)

i bought 3 bottles of vodka last night, drank them all, and in the morning i had a headache and threw up several times, that vodka must not be fresh,


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## Lynx_Arc (Apr 25, 2012)

mattp said:


> Ahhh, that'll be the problem, he's sitting waaaay too close.
> 
> But seriously, I can't see how you can 'damage' your eyes physically by looking at a screen.


Before the 90s they were not concerned about monitor radiation and some people who sat in front of monitors all day did get some damage to their eyes etc. I don't think it was widespread but it was enough of an issue that during the 90s they started to pass regulations on the radiation monitors (CRT) put out and for the most part monitors (CRT) made in the mid to late 90s and beyond were pretty much safe for the eyes etc. LCD (includes LED) monitors do not radiate anything but light from them. The LCD monitors use fluorescent tubes (CCFL) to shine light through the LCD display while LED monitors use white LEDs instead of the fluorescent tubes. None of those monitors are harmful to the eyes any more than it is harmful to the eyes to sit in a room with fluorescent or LED lighting. 
I think a lot of the time people go from a lower resolution CRT (tube) monitor to a high resolution LCD/LED monitor and don't realize that eveything just shrunk (got smaller) because the default resolution and actual physical size of fonts and pictures are smaller. When you get a new monitor you need to adjust the screen resolution to your liking and sometimes adjust the font defaults to match. As for "heat" from an LED vs a CRT... the CRT puts out a LOT more heat than any LCD monitor does.


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## tatasal (Apr 25, 2012)

jtr1962 said:


> Make sure the monitor is set to its native resolution. If it's set to anything else, it'll look like crap and possibly give you eyestrain.



What does native resolution mean and how do you set it?


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## idleprocess (Apr 26, 2012)

tatasal said:


> What does native resolution mean and how do you set it?



"Native resolution" is the maximum resolution of the panel. Running it at less will be a bit hazy since the panel must try to display at a fraction of its resolution and will use some sort of interpolation method to reduce the visual impact. It's an imperfect technique since the resolution being supplied by the computer is almost never a neat whole-number divisor, which would allow for each desktop pixel from the computer to occupy a whole number of physical pixels on the display; instead each desktop pixel sits within the boundary of multiple physical pixels.

This is usually accomplished by some tool in the operating system. Most Windows machines can be adjusted by right-clicking on the desktop and selecting "properties" ("screen resolution" in windows 7, perhaps also in Vista). Not sure about OS X nor the various *NIX'es.


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## idleprocess (Apr 26, 2012)

dc38 said:


> Also, there's your problem in your post...you use the computer for 7 HOURS A DAY.



That's pretty much mandatory in many desk jobs these days... 

I'm looking at LCD monitors 8 hours a day at work then sitting in front of one at home as well. Can't say the decline in my eyesight over the years is due to this factor exclusively - aging in general is also playing a part.

I miss the beautiful CRT I had at my last job (some 8 years ago now) - was the easiest on the eyes that I've ever had. Flipside was that I was in and out of the production floor regularly every day, so I didn't just stare at that monitor for 8+ hours a day.

At least at my present work I have a good monitor mount that keeps the LCD's at eye level. I try not to just sit there and stare at them constantly, but it can't always be helped.


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## assassin966 (Apr 26, 2012)

Im not close to the monitor im far from it 2 meters almost 1.81 im far from my 23 inch monitor and before i had samsung p2470HD wich now i switched back i dont want lose my eyes on the LED monitor maybe there was a problem or a glich with the monitor or a settings the monitor was set to full 1080p resolution 1920x1080 as before i had the same monitor only now i have LED back-light the problem with my eyes is when i look outside when i move with my eyes i see like there is something inside my eyes some pieces that looks like broke from my eye and its inside when looking at white color completly i can see that beast when i look my eye in a mirror i can see red vessels that are connected to my pupil wich i didnt had before i seen normal with no any problems before the LED !! i will tell you my monitor settings of samsung px2370 the magic color was set to intelligent magic lux was set to medium and the image response time was set to fastest !!!


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## 127.0.0.1 (Apr 26, 2012)

assassin966 said:


> Im not close to the monitor im far from it 2 meters almost 1.81 im far from my 23 inch monitor and before i had samsung p2470HD wich now i switched back i dont want lose my eyes on the LED monitor maybe there was a problem or a glich with the monitor or a settings the monitor was set to full 1080p resolution 1920x1080 as before i had the same monitor only now i have LED back-light the problem with my eyes is when i look outside when i move with my eyes i see like there is something inside my eyes some pieces that looks like broke from my eye and its inside when looking at white color completly i can see that beast when i look my eye in a mirror i can see red vessels that are connected to my pupil wich i didnt had before i seen normal with no any problems before the LED !! i will tell you my monitor settings of samsung px2370 the magic color was set to intelligent magic lux was set to medium and the image response time was set to fastest !!!




ummm, no damage from screens will do that. You must seek an_ Opthamologist_ who will dilate your pupil and look
at your retina. What you describe -may- be severe internal damage which can be completely fixable but you
must act immediately. Loose retina or damaged blood vessels can be fixed with lasers. Go now and fork over
the loot and have your eyes checked pronto. You also describe surface irritation which again, has some other cause.

That or it just a common floater [or three or a dozen] and it is 100% normal. everyone has some floaters.


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## Th232 (Apr 26, 2012)

127.0.0.1 said:


> ummm, no damage from screens will do that. You must seek an_ Opthamologist_ who will dilate your pupil and look
> at your retina. What you describe -may- be severe internal damage which can be completely fixable but you
> must act immediately. Loose retina or damaged blood vessels can be fixed with lasers. Go now and fork over
> the loot and have your eyes checked pronto. You also describe surface irritation which again, has some other cause.
> ...



^This. See an opthamologist now. If it is retinal detachment the longer you leave it the worse your chances of recovery are.

And I also highly doubt this was caused by the LED screen. Sounds to me like this was just bad timing.


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## assassin966 (Apr 26, 2012)

Th232 said:


> ^This. See an ophthalmologist now. If it is retinal detachment the longer you leave it the worse your chances of recovery are.
> 
> And I also highly doubt this was caused by the LED screen. Sounds to me like this was just bad timing.


 i was in ophthalmologist he sayed everything is ok it just that i never had floaters im 20 years old and this has started when i started using led screen just after few weeks it started to appear inside my eye this really enjoys me i cant concentrate on anything when i see this !! an ophthalmologist gave me blink eye drops to refresh my eye i been using it over 1 month it just keep going worse if there is anyway i can clean it with something in Croatia and how much would it cost? i just dont understand how LED can do this to me is there any reason possible for the LED monitor to create this floaters in my eyes it cant be something else i would like to take back my LED monitor but i dont know will i lose my eyes or this keep going worse (i payed for that monitor 450$ here in croatia now i cant get refund or it will just keep staying in a garage with no use im scared to use that monitor again).


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## alpg88 (Apr 26, 2012)

127.0.0.1 said:


> That or it just a common floater [or three or a dozen] and it is 100% normal. everyone has some floaters.


lol, sure, especially after lots of popcorn, 

sorry, couldn't resist.


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## dc38 (Apr 26, 2012)

assassin966 said:


> i was in ophthalmologist he sayed everything is ok it just that i never had floaters im 20 years old and this has started when i started using led screen just after few weeks it started to appear inside my eye this really enjoys me i cant concentrate on anything when i see this !! an ophthalmologist gave me blink eye drops to refresh my eye i been using it over 1 month it just keep going worse if there is anyway i can clean it with something in Croatia and how much would it cost? i just dont understand how LED can do this to me is there any reason possible for the LED monitor to create this floaters in my eyes it cant be something else i would like to take back my LED monitor but i dont know will i lose my eyes or this keep going worse (i payed for that monitor 450$ here in croatia now i cant get refund or it will just keep staying in a garage with no use im scared to use that monitor again).



Have you been conducting any other kinds of activities? Maybe blunt force trauma to your head? I read somewhere that some boxers lose their sight to retinal detachment. Also, CRT's have flicker, maybe you just never noticed the floaties before? Or maybe perhaps you're a troll. . . Trolls tend to be visually challenged. . . Anyways, on a more serious note, don't use the computer so long and you'll be okay! Either that or take a break and look at some greenery and eat carrots


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## alpg88 (Apr 26, 2012)

there can be few reasons your eyesight worsens, from blunt force trama, nerve damage, to high blood pressure. there is such setting as refresh rate in monitors, may be it has something to do with your eyes? try changing that if you can, not sure if it'll help but who knows.


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## assassin966 (Apr 26, 2012)

so you are saying that LED cant do that i often do a break after 3-4 hours of using pc a 3 hours breake than again playing for 3-4 hours i just noticed it when i started using LED monitor before that my eye was clear if its possible with the response time why do i have option normal fast and fastest ?


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## blasterman (Apr 26, 2012)

> there any reason possible for the LED monitor to create this floaters in my eyes



Sudden floaters = possibility of glaucoma. The older you are the more likely the diagnosis, and one big way to reduce the problem is to get away from the monitor and get more excercise to get your blood pressure down.

Blaming this on an LED backlit monitor is pretty absurd. The chemicals leaching from the plastic case are more likely to cause health problems. If eye issues arose strictly from the intensity factor of a modern monitor then you'd likely catch fire and explode if you went out doors on a sunny day.

I'm seeing more and more 'LED's cause eye damage' threads in various forums, and they all link to psuedo science regarding blue light being having the equivelant energy levels of gamma rays and such. Compare to halides and fluorescent tubes LED's actually have a more evenly distributed blue spectrum and also lack the UV spikes of the other light sources.


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## 127.0.0.1 (Apr 26, 2012)

all an LED monitor can do is cause eyestrain they cannot damage the eye unless you try really hard
and use the monitor in a way not described in the manual (like poking your eye with it)

eyestrain....when your brain has had enough noise, and your vision get 'tired',
starts to go double, and/or you get headaches or eye-aches from the eye muscles saying fuggeddabout it I need a rest

BUT
what you describe are floaters. most people can lay on back and look at fluffy clouds and see floaters.

I bet they were always there, it is just now you have a new screen and you can see floaters with this new screen
and your previous screen didn't have the correct type of light for you to see floaters.

floaters are normal, everyone has some. sudden appearance of new floaters is not good and indicates:

blood pressure problems
poorly controlled diabetes [or systemic dehydration for another reason]
eye trauma
head trauma

or you just haven't seen then before, and now you have a nice flat white background and now see floaters you always had
..as I type this now on a LCD monitor, I can chase 2 floaters around.....it is normal. stop looking at them and focus on something else


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## assassin966 (Apr 26, 2012)

127.0.0.1 said:


> all an LED monitor can do is cause eyestrain they cannot damage the eye unless you try really hard
> and use the monitor in a way not described in the manual (like poking your eye with it)
> 
> eyestrain....when your brain has had enough noise, and your vision get 'tired',
> ...


 Than i really dont know what is it than i never had it before it just hapens to be BAD TIMING I GUESS? well i will put back my led monitor back if it keep going worse i will go to doctor again if it make it worse than i really dont know what im gone do next probably smash the led into pieces or kill myself this is enjoying me alot when i see it i just cant concentrate on anything ah very well i hope you are right if you are not righ i probably go blind because this HDTV is very bad quality and when rebooting it it all resets thats why i buyed new monitor


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## RoGuE_StreaK (Apr 27, 2012)

Yup, just coincidental timing. I got my first noticable floater relatively recently, I got extremely paranoid about it having never really heard of it before, it shouldn't happen to me, I'm young(ish...), etc., but after lots of googling and talking to people, you find out that they are extremely common, and you learn to generally not notice them. Supposedly sometimes they disappear with time, or you can get zapped by a laser to burn them up.

Red veins are most likely just due to dryness and/or overuse, blink often and get some eye lube (eye drops). But could also possibly be connected with a pterygium, which is a growth over the eye caused by dryness and/or UV light. Usually extremely slow growing, I've had one for probably 15yrs and it still hasn't gotten to a stage where it effects sight, when it needs removal (and I've been to a fore-most specialist in this field). Mine was caused by years of surfing.


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## HarryN (Jun 2, 2012)

There are different levels of eye doctors, at least in the US. Some are primarily for doing simple checks of your eyes and making glasses. Some are real physicians / doctors. Consider going to a higher level eye doctor to double check.


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## hank (Jun 2, 2012)

> Opthamologist 

That's a real eye doctor -- not an optometrist.

Floaters and the rest you describe are normal, and increase with age, and once you start to notice them you'll notice them more and more. Also if you're keeping your head in exactly the same position for a long while the stuff settles down to the bottom of your eyeball then gets disturbed when you move around -- and it gets in between the lens and the retina making those floating shadows.

Remember the retinal image is "upside down" -- your brain flips it over to match reality. So when a lot of crud settles down to the bottom of the eyeball, it's just outside the _top_ of the image as your brain perceives it. Move your head around after a long period motionless and it'll all seem to be floating around again then rising up.

It's not your LED monitor.
It's not damage.

It's normal aging.

If a real opthalmologist -- a real medical doctor specializing in vision -- finds anything, they'll advise you what to do.
An optician (eyeglasses-maker) or optometrist (eyeglasses-vision-measurer) don't have the same expertise to help you.


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## TEEJ (Jun 2, 2012)

Yeah, its like the cases where people experience something, and, as human nature dictates, they try to figure out why.

If anything just happened before the experience in question, the first thing people do is assume a cause and effect relationship. 

For example, someone tries a new sunscreen, and gets a violent headache, and concludes it must be from the sunscreen. 

Someone was out doing yard work in the hot sun, cleaned their eyeglasses, and the metal frame snapped....and they told me it must be from the heat/hot sunlight making the titanium brittle.

And so forth..."I changed this, and then that happened, so, obviously, this caused that".



Its very similar to "Sinceyou's" in the repair industry.

IE: Ever since you changed my oil, my left rear tire is vibrating....

Ever since you changed my tires, my muffler been making noises...



Same pattern - assumption that if one thing preceded the other, the first caused the second.


In some cases, its at least POTENTIALLY true of course, "Ever since you hit me in the head with that bat, my head's been hurting like a MoFo..."

The other times, well, not so much.


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## recycledelectrons (Aug 5, 2012)

I've had the same issues as the OP.

(1) Does this happen more when you are tired? (Don't just try to remember; test it for a week.)

(2) If you are concerned that your monitor is damaging your eyes, try to replace it. Your vision is worth more than a used LCD. (Do you still have your old monitor?)

(3) Some monitors are much better than others. Unfortunately, the good ones are very expensive. Even worse, you have to buy a monitor and use it for weeks to know if it reduces your eye strain. Could you ask your boss to swap your monitor with another one?


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## SemiMan (Aug 6, 2012)

recycledelectrons said:


> I've had the same issues as the OP.
> 
> (1) Does this happen more when you are tired? (Don't just try to remember; test it for a week.)
> 
> ...




I am going with Lynx's first reply. Old monitor of a tolerable size and low resolution, hence big characters. New monitor bigger, but likely 16:9 and HD ... hence small characters. Just like my laptop that I am straining on right now.

Depending on the OS, you can set the zoom setting for text to larger which will go a long way. Always can zoom browsers, etc.

You can get glare off a monitor depending on the surface too.

Even the lowest cost monitors, assuming you have a digital connection, are pretty tolerable these days in terms of viewing angle, crispness, etc. The more expensive ones have even better viewing angle and more accurate colors across viewing angle, but straight on, at least in terms of eye fatigue, are not exceptionally better. That all goes away with an analog connection which can be pretty bad on a cheap monitor in terms of fuzziness, color banding, noise, high frequency jitter, etc.

Semiman


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## Gibrango (Apr 24, 2013)

Almost a year later, I found this post because I am experiencing the same problems. Thought I'd resurrect it with my $0.02. My suspicions with LED monitors (as opposed to the CCFL LCD or CRT monitors) starts with the fact that the LEDs emit light in pulses to control the brightness, called pulse width modulation. Secondly, I remember a year and a half ago, there was a thing going around where you could see the veins in your eye by making a pinhole with your thumb & index finger and shaking it around http://gizmodo.com/5872157/freakythis-simple-trick-lets-you-see-the-blood-vessels-in-your-eye. The concept there is that the veins are always there and your brain ignores things that stay stationary for a long period of time; like your nose and these veins. By doing the pinhole shake, you cause your brain to re-see them temporarily. So putting that trick together with the pulsing nature of the LED monitors made me consider that the floaters were always there, but are made more visible by the LED screen's pulses. It's interesting though, because I don't get this on my laptop, which has a RGB LED array. I don't get it on my iPad2, but I don't know if it is a CCFL backlight. it just happens on my ViewSonic value series LED monitors. Wondering if the OP had any thing further on his experience, but I can't PM him - maybe because I'm a freshly registered member.


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## SemiMan (Apr 24, 2013)

Gibrango said:


> Almost a year later, I found this post because I am experiencing the same problems. Thought I'd resurrect it with my $0.02. My suspicions with LED monitors (as opposed to the CCFL LCD or CRT monitors) starts with the fact that the LEDs emit light in pulses to control the brightness, called pulse width modulation. Secondly, I remember a year and a half ago, there was a thing going around where you could see the veins in your eye by making a pinhole with your thumb & index finger and shaking it around http://gizmodo.com/5872157/freakythis-simple-trick-lets-you-see-the-blood-vessels-in-your-eye. The concept there is that the veins are always there and your brain ignores things that stay stationary for a long period of time; like your nose and these veins. By doing the pinhole shake, you cause your brain to re-see them temporarily. So putting that trick together with the pulsing nature of the LED monitors made me consider that the floaters were always there, but are made more visible by the LED screen's pulses. It's interesting though, because I don't get this on my laptop, which has a RGB LED array. I don't get it on my iPad2, but I don't know if it is a CCFL backlight. it just happens on my ViewSonic value series LED monitors. Wondering if the OP had any thing further on his experience, but I can't PM him - maybe because I'm a freshly registered member.




Or more likely you don't have a digital connection to your monitor and it is a bit blurry?

The PWM frequency would at a minimum be several multipliers of the refresh rate and beyond what your optical system will process. Keep in mind all DLP projectors pulse as well.

Semiman


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## MikeAusC (Apr 24, 2013)

I've had minor Retinal Detachment in both eyes, separated by 12 months, that produced Flashing and Floaters.

The Opthalmologist made it clear that they aren't caused by anything you look at.

If you do get Flashing and Floaters, see an Opthalmologist urgently. Retinal detachment can lead to total blindness if untreated.


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## Gibrango (Apr 25, 2013)

SemiMan said:


> Or more likely you don't have a digital connection to your monitor and it is a bit blurry?
> 
> The PWM frequency would at a minimum be several multipliers of the refresh rate and beyond what your optical system will process. Keep in mind all DLP projectors pulse as well.
> 
> Semiman



To Clarify further here, it is not an eye-strain problem. It cracks me up that others think that seeing floaters comes from something being blury or maybe you're running 1024x768 on a 1680x1050 screen. I am an IT Consultant, so I can with all authority assure you that the monitors are not blurry due to resolution mismatch or signal quality. I have excellent vision, recently checked at the ophthalmologist (though it _is_ Kaiser Permenente, so insert digs about the quality of their staff here). I always run at a monitor's native resolution. In the LED screen's case, I have 2 side-by-side 24" 1920x1080 WLED screens, one uses DVI, the other is VGA, off my docking station. My laptop is a 17" 1920x1200, again, running native on RGBLED. I previously used a 15.4" 1920x1200 laptop that was lit by a CCFL, and it was not blury. That older laptop drove 2 22" 1920x1080 CCFL viewsonic monitors and they did not cause me to see the floaters. But both of my 24" monitors are causing the issue. With regard to the PWM, I would have to disagree. It clearly depends on how bright I have my monitor. At the brightest setting, the phemonenon is les likely to be perceived. My displays are at 50% brightness, meaning the pulsing is more pronounced. At 10% brightness, it would be even more so. I think that depending on the quality of the manufacturer, differently sourced PWM modules would have differing quality, and I would expect a value-priced monitor to have a cheaper PWM controller. Haven't you noticed that as you are driving and looking side to side, that the tail lights on late-model luxury cars have that stuttering effect? I would tend to think that would prove that the human eye can perceive the pulses in an LED light source. Check out this link : http://www.tftcentral.co.uk/articles/pulse_width_modulation.htm It says that PWM can be as low as 90 cycles per second, and up as high as 400hz.


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## Gibrango (Apr 25, 2013)

MikeAusC said:


> I've had minor Retinal Detachment in both eyes, separated by 12 months, that produced Flashing and Floaters.
> 
> The Opthalmologist made it clear that they aren't caused by anything you look at.
> 
> If you do get Flashing and Floaters, see an Opthalmologist urgently. Retinal detachment can lead to total blindness if untreated.


When I first started seeing the floaters, and googled the symptoms, that's the first thing I though of. But I am not seeing flashes, and I don't see an increase in floaters. Its just that when using these WLED monitors, I am distracted by my floaters. As soon as I step away, or even look away for a few seconds, They're gone. So I am not under the impression (as the OP originally was) that the WLED monitors _caused_ my floaters, so much as they made the existing floaters I had more noticeable during their use. If it is PWM related, I can probably minimize the effects to the extent possible by turning the brightness all the way up on the displays and turning the brightness down in my video card driver. I may give that a shot.


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## uk_caver (Apr 25, 2013)

Gibrango said:


> Haven't you noticed that as you are driving and looking side to side, that the tail lights on late-model luxury cars have that stuttering effect? I would tend to think that would prove that the human eye can perceive the pulses in an LED light source.


I think there's a slightly different thing involved there - with the eye scanning at a high speed past a fixed small PWM source with high contrast with its surroundings, the PWM nature will be visible whatever frequency it is at, up to the point where the PWM frequency&duty cycle is such that the 'off' period is shorter than the time the eye takes to change angle by the angular width of the object.

That doesn't really relate to things like persistence of vision or flicker frequencies, it's just an issue of timing vs. geometry


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## degarb (Apr 25, 2013)

assassin966 said:


> I was using pc for over 10 years never had any problems before but now after buying an LED monitor it started to damage my eyes i have notice after buying samsung px2370 using it for like 2 months now i have my eyes damaged and never had tham before i have buyed LED monitor becouse i heard that it has better picture quality and its better for eyes but now after using LED monitor i have notice that its damaging my eyes please tell me how is this possible or im allergic to LED back light i have been no more using pc more than 6-7 hours per day and it damaged my eyes !



There is a little knob on the monitor, to turn down the brightness.

Time and age will destroy your eyes, btw. Actually, time will kill and destroy us all. I tried suing time, but her accounts were empty.


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## SemiMan (Apr 26, 2013)

uk_caver said:


> I think there's a slightly different thing involved there - with the eye scanning at a high speed past a fixed small PWM source with high contrast with its surroundings, the PWM nature will be visible whatever frequency it is at, up to the point where the PWM frequency&duty cycle is such that the 'off' period is shorter than the time the eye takes to change angle by the angular width of the object.
> 
> That doesn't really relate to things like persistence of vision or flicker frequencies, it's just an issue of timing vs. geometry



I can do the hand wave, head shake ... on purpose and see flicker in the odd bulb and in some tail lights. Normally I do not really notice. I am unable to get that to happen on either of my LCD monitors or laptops set to mid level. I will scope it when I am less busy.

Caver, I am not sure if what you are stating is supporting or not supporting PWM impacting the imaging of floaters? To see them at all is as much an optical problem as anything as normally they would be so blurred out as to be invisible. The monitor is a wide area light source and the floaters would not experience any on/off angular issues as your head moved.

PWM frequency may be impacted by monitor cost, but not pwm "quality". They are likely pulsed in the KHz+ range, well beyond the photo speed response of the ocular system.


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## fyrstormer (Apr 26, 2013)

If you're seeing an afterimage of the blood vessels in your retina, it is most likely caused by lighting in your peripheral vision, entering your eyes at a sharp angle and causing the blood vessels to cast long shadows on your retina. This is a well-known phenomenon, and you can easily replicate it by shining a flashlight across your face from the side.

As for the original poster's problem, there is nothing at all about LED backlighting that can cause vision damage. If his eyes really are degrading, it's almost certainly due to an eye disease he doesn't know he has yet. He might also be suffering from some temporary eye-straing because his new screen has such a high resolution that he's straining his eyes trying to focus on fine details. It's probably some of both.


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