Monitors and Our Health
A warm welcome to curious individuals who are interested in the damaging effects of Liquid Crystal
Displays! Excuse possible spelling mistakes. My main language is Ukrainian.
There is an increasing number of people that are suffering from LCD monitors and other luminescent-
based displays. The main symptoms are eye discomfort, burning eyes and headaches, but there are many
more. Often, these symptoms develop gradually after actively using a new LCD for a longer period of
time. It may start as slight eye discomfort, maybe combined with small headaches, and transform over
time to severe eye pain while using the monitor. The eye pain may last for the rest of the day, even
after not using the LCD anymore, or it may become chronic and won't go away and get worse with every
time one uses an LCD or an other monitor. Also headaches, nausea, dizziness and a whole variety of
other symptoms may be felt by the user of an LCD.
I suffered from something that can be described as tired eyes. After my uncle gave me his notebook
with an LCD display and "brainwashed" me with his speech about how much "better" LCDs are than CRTs,
I started using LCD monitors. I was used to spending a lot of time with watching television and
using the PC, but both were CRTs. For some reason I didn't use the new LCD much at first. But when I
started to use the new LCD technology for more hours a day than usual continually, my eyes started
to feel weird. This weird discomfort grew into eye pain. Then I started to have this eye pain even
when I wasn't using any monitor at all. I also couldn't use any other type of monitor after I
spoiled my eyes with the LCD. What was the reason for my illness? I was pretty sure that it was the
LCD, because it only got worse when I used that monitor. But there was something else. One day I
found out that my sensitivity to LCDs comes from my sick nervous system. I was sensitive to all
kinds of things, but mostly to luminescent light (I explain why during the course of this page).
Every kind of display that I tried was based on luminescence and I couldn't use any of them. I
couldn't even look at my mobile phone's display. I tried CRTs, Plasma, LED LCDs, an AMOLED Display
(on a Samsung mobile phone) and all of them hurt my eyes. The one that I could use the most was the
CRT display, but only for about 15-30 minutes a day. Afterwards my eyes would hurt double as much
until I went to bed. Sleep and abstinence seamed to be the only thing I could do to improve the
situation. Later, I found out that I had to avoid fluorescent tubes in large malls and many other
places as well. During that time I actively searched for a monitor solution to at least be able to
use the PC or to watch television. I thought about it every day and after searching the Internet for
information (with my limited abilities) and conducting many experiments (trial and error), I
concluded that the thing that caused these symptoms was light.
To be able to better understand this problem I recommend reading the information about LCD
Discomfort on this site: www.cloanto.com/users/mcb/19960719lcd.html
Incandescent Backlit LCD
Knowing that I never had problems with incandescence and that my problems were caused by the light
from inside the monitor (fluorescence), I thought of ways to replace the bad light with the good
one. After taking the LCD apart together with my father, we saw that this could be done. It was only
a matter of the right design and carefulness, because the insides of an LCD monitor are incredibly
fragile. I chose a design that would minimize the risk of ruining the monitor and the monitor was
done in less than a week.
Since my father and I rebuilt the ViewSonic VA1926W LCD to work with incandescence instead of a cold
cathode fluorescent lamp (CCFL), I can look at my display much longer. Now I can look at it all day
if I want to, with only slight eye pain after many hours of use.
After I modified my notebook to work with incandescent light as well, I found that it gave me
terrible eye pain. So there was a second problem besides the backlight that the notebook had to a
larger extent, because I didn't feel 100% comfortable with the ViewSonic either. What could have
been the second problem? Many overlook and underestimate it when searching for the reasons of their
symptoms. It is the grid between the pixels (pixel density) that causes a lot of trouble, at least
to me. I found this out by comparing the two incandescent monitors of mine, one of which I could use
and the other not. I found the notebook to have a noticeably larger grid between the pixels and this
was the reason for my eye pain.
After I found the problem, I searched for a solution for this final problem in LCDs to be 100%
symptom-free with my LCDs. The idea came to me when a diffuser fell out of the display one day. I
thought the diffuser could blur the grid enough to make it stop having an effect on me but not too
much for the content of the screen to get blurry. And this is just what I have accomplished. I just
applied oil to the diffuser to make it fully transparent (wiped most of it off with a towel) and
stuck the diffuser to the screen of my ViewSonic and later to my notebook. After I did this my eye
discomfort fell to zero, both, in my ViewSonic and my notebook. The results were clear - the grid
between the pixels was the last problem in the way of complete comfort for me. And the smaller the
grid, the less discomfort I have. Having only little discomfort with the ViewSonic display with a
pixel per inch (PPI) value of about 90, I think that I would have much less discomfort with a
display of a PPI value of 108 (the bigger the PPI value, the smaller the grid) with a flicker-less
backlight and without a diffuser.
Although incandescent light plus a diffuser helped me to be able to look at my LCDs as much as I
want to with absolutely no symptoms, it is still possible that my methods won't help you, although I
currently believe that many people who suffer from similar symptoms as I do with standard LCDs would
find 100% relief, just as I do, just probably not all. It is also not excluded that some new
technologies may be introduced to newer LCDs that my two LCDs don't have. For instance 120 Hz LCDs,
which may create these 120 Hz by inserting black images and thereby creating flicker. I can at least
tell you that one of my incandescent LCDs has temporal dithering and is causing me zero health
Why is Luminescence Worse than Incandescence?
Since every display that I tried used luminescence and caused my eyes to hurt, I can conclude that
luminescence can be harmful. But what makes it so bad?
Through various experiments I can rule out the following factors:
The incandescent backlight in my modified LCD gets just as polarized as the luminescent backlight
Spectrum/too much blue in the spectrum
I used a filter that removed the complete blue part of the spectrum.
Intensity of light
I used a lot of combinations of brightness and contrast, but until I replaced the fluorescent
backlight, my eyes refused not to hurt.
What other factors are there that make the light waves so different?
Flicker seems to be the main troublemaker. Every kind of luminescence that I encountered had
flickered. CRT TVs and monitors, Plasma TVs, AMOLED & OLED Displays, LED and CCFL backlit LCD
monitors (due to backlight dimming) and fluorescent lamps flicker. Think about it! The main symptoms
that people report having from monitors and fluorescent lights are headaches, eye strain and eye
discomfort. What main symptoms do people experience when under flickering light? It's headaches, eye
strain and eye discomfort. I think we have a match here.
While staying on the subject of flicker I would like to mention that the brain seems to also react
to "static repetitive geometric patterns" or "spatial patterns" of the monitor, better known as the
grid between the pixels, very similarly as to flickering light. Such spacial patterns, when thick
enough and moving, can even cause an epileptic seizure in epileptic people, just as flicker can. See
slide 4 here:
While luminescence isn't bad itself, the bad qualities that it can have can cause terrible motion
Here is some info for those who suffer from the flicker in fluorescent lamps:
Flicker and the Nervous System
Some luminescent-based monitors flicker at very high frequencies (100 Hz - 20 kHz and even higher)
and are not consciously perceivable by the human eye. This is why many "experts" claim that the
element of flicker is not likely to be the cause of many people's problems. But this flickering
light is noticed unconsciously and it has negative effects on the nervous system (read the
"Interesting Quotes" that come later). Almost in every case of someone feeling pain in his or her
eyes because of nervous system related monitor problems, the ophthalmologist cannot detect anything
wrong with the person's eyes. How can eyes hurt, if there is nothing wrong with them? My eye doctor
admitted that in children, whose nervous system is not fully developed yet, flicker from old CRT TVs
may cause symptoms that are similar to mine, but didn't consider the nervous system being fault in
my case. Later, an other doctor detected that my nervous system was in very poor shape. Isn't it
logical to assume that high frequency flicker too can cause the same or even worse damage to an
adult's nervous system once it is weakened by fear, stress, etc.? Here are some phrases that are
relevant to know:
"All illnesses go through the nervous system.
"Pain only exists in the brain, but we feel it in our hands, feet, eyes etc.
"The eyes are the only part of the body that is directly connected to the brain.
"The central nervous system consists of the brain and the spinal cord."
People with a very sick
nervous system tend to experience pain in parts of the body. An example is a man with a seriously
sick nervous system. Because of it, he had experienced pain in a certain organ. The pain was so bad
that the organ had to be surgically removed. Unfortunately, that didn't help, for he continued to
have pain where the organ once was. He continued to have pain until he found out what really was
sick and what needed to be treated. The pain started to go away when this person treated his nervous
system. I also have a distant relative that gets rashes when he is in a very nervous state. These
are good examples to show how important a healthy nervous system is and what can happen if it isn't.
These pains originate from the nervous system alone, without physical cause. The nervous system
inappropriately gives the command of pain where there is none. You may have completely healthy eyes,
but if the nervous system says so, they will hurt. An example of the nervous system creating pain in
healthy organs is any psychosomatic symptom. Psychosomatic symptoms are usually caused by emotions
that weren't allowed to surface, for instance when you are very angry with someone and that someone
is your boss and you suppress these feeling to not get into trouble. These suppresses emotions
remain in your body and cause pain in certain parts of your body. The only difference between
psychosomatic symptoms and LCD symptoms is that the symptoms are caused or amplified by high
frequency flicker. The question that arises here is if the "non-existent" symptoms are harmful. And
that I don't know. Also, the LCD symptoms are not 100% psychosomatic, since the term implies that
the symptoms are completely coming from the mind, as in us subconsciously fearing that we might get
headaches and eye pain from LCDs and that that alone causes the pain. If that were true, than these
symptoms would be purely psychosomatic. But we all know it isn't so. Many were convinced that LCDs
could not cause eye pain and never suspected it would before they tried one. We get reports about
people trying many monitors with eventually one coming along that causes them no symptoms. Why would
they have a fear of many monitors and no fear of the certain one that causes no symptoms. Also, many
were completely sure that the new LED backlighting would solve their problem and yet they couldn't
use them. And how would you explain that some monitors cause less intense symptoms while other ones
cause more intense symptoms? There is no doubt that flicker is one of the factors that causes or
makes these nervous system symptoms worse. Why is flicker causing it? The answer is that our sensory
information needs to be processed somehow and 200 flickers a second is simply too much to process
for some people. 200 flicker a second is 12000 flickers in a minute. Many start getting symptoms
after 15 minutes - that's 180000 flickers. The difference between about 50-100 Hz of CRT flicker and
about 200 Hz of the LCD's CCFL and LED backlight (numbers vary with different monitors, but are
about 200 Hz in almost all LCDs) is the key in why many people are fine with CRT monitors, while
they can't use CCFL and LED backlit LCDs. If you have a CRT with 85 Hz of flicker, then you only get
76500 flickers per 15 minutes. Compare that with 180000 LCD flickers per 15 minutes. But wait, - you
might say - isn't a higher frequency supposed to be better? Or you might have experienced how your
eyes hurt less on a CRT with 85 Hz rather than with 60 Hz. The answer is that it is true that a
higher frequency is better for the eyes directly, but we are talking about the eyes hurting through
the nervous system, not directly as in the muscles reacting to flickering light. The eyes stop
directly reacting to flicker at about 100 Hz (this number is solely my conclusion and not
universally accepted). From there on they just convey the flicker information to the brain/nervous
system without the eye muscles contracting and releasing as it seems to happen with low frequency
flicker. I noticed that of all of the displays that I had, I could watch a 50 Hz CRT TV the longest.
It makes sense, since I had healthy eyes with my eye muscles not being tired. My only problem was
the nervous system pain, which 50 Hz still created, but it is way easier for my nervous system to
process 50 flickers a second that 200. It seems that CCFL LCDs flicker a lot faster than CRTs, thus
making you sick faster, and they throw a lot more of the bad light at you (because black pixels leak
light), excelling the process of getting sick even more. Most LCD's backlight's flicker doesn't even
spend the same time in the "on" state that is does in the "off" state when brightness is reduced.
The off states are made much longer when you reduce the brightness, which makes the flicker more
intense and harder to bear. There should be a label on each CCFL backlit LCD with a warning that the
product's backlight unproportionally turns itself on and off a couple of hundred times per second
and that it may have negative impacts on your health. But we don't see it there for some reason.
Update: Be especially careful with antidepressants! I took Zoloft for 7 months and it caused me to
have headaches with LCD. The aftereffects of antidepressants are truly horrible. I never had
headaches with LCDs until I took Zoloft for 7 months. The drug seems to have taken much joy out of
my life and made me feel like a zomby. My mind feels fogy and my consciousness altered. These
feelings last long after one stops taking the drug and may often be irreversible. I am lucky that I
only took it for 7 months. A special diet might help repair my brain after antidepressants. If you
are taking or considering taking antidepressants, please read these testimonies:
LEDs can work without flicker, even the invisible one. Many people with LCD problems saw a promising
solution to their problems in the new LED technology, but were often disappointed. Many believed
that LEDs wouldn't flicker at all, because they were capable of being "on" all the time. But the
manufacturers managed to introduce flicker into the world of LEDs after all. Instead of dimming them
in a way that would make them completely flicker-free, they decided that the best way of dimming the
LEDs behind the LCDs would be to use Pulse-Width Modulation. Here is a quote from reuk.co.uk/LED-
"A far superior method of dimming LEDs is to use Pulse Width Modulation (PWM).
With PWM strings of LED bulbs can all be driven with the recommended forward current, with the
dimming achieved by turning the LEDs on and off at high frequency - so fast the human eye cannot see
the strobing effect. The longer the on periods are relative to the off periods, the brighter the
LEDs will appear to the observer.
Duty Cycle is a percentage measure of the time that the LED is physically on. If, for example, the
LED cycles ON for 9/1000 of a second, and then OFF for 1/1000 of a second, the duty cycle is 90%:
90% of the time it is ON, and 10% of the time it is OFF. Therefore, the intensity of the light will
be approximately 90% of its undimmed level."
Many of the people that tried LEDs as the solution to
their monitor problems were unaware of the PWM flicker and they started to dislike LEDs in general,
thinking that they are "allergic" to LEDs. But LEDs in LCDs aren't really what's producing the
light. The LCD contains blue or ultraviolet LEDs with phosphor coatings. The LEDs shine upon the
phosphor with their invisible UV rays or blue color and the phosphor starts glowing "white". So
technically, if you thought that you were somehow allergic not to the flicker, but to the LEDs
themselves or fluorescent light for that matter, then thats not correct. You only been exposed to
phosphor glowing, not LEDs, CFLs, CCFLs or CRTs. All of the mentioned light sources use phosphor. If
you should have a problem with phosphor, then you should be equally sensitive to all of the light
sources mentioned above, but thats often not so - many claim that they can use CRTs much longer than
LCDs with CCFL or LED backlight and vice versa. I believe this also answers the question of "Are LED
monitors better/worse than CCFL LCDs". The answer is that they're almost exactly the same, since
they use the same PWM dimming, only difference being that LEDs turn off instantly and go on
instantly as well, while the transition from on to off to on in CCFL LCDs was not so rapid, which
makes LEDs even slightly worse.
One new problem in first LED monitors that came out seemed to be that the PWM frequency was often
extremely lower than compared to CCFL LCDs. It was so low that those with no problems with CCFL LCDs
started to have similar symptoms with LED LCDs. A too low frequency, while less bad from my
experience for the nervous system, can be bad for the eyes directly, especially with a low duty
cycle. Here is an example of how low PWM can go:
"CCFL tubes apparently have a PWM
frequency in the khz, while LED's have a PWM frequency typically between 90hz and 500hz (one poster
measured the x200 Tablet at 90hz; another measured two other laptops at 500hz; I have measured a
Toshiba A605-P10 at 200hz)" Because many people have had a bad experience with LEDs in one device or
another they completely lost hope in LED backlit LCDs. They shouldn't have completely! There still
is a way to solve the flicker problem for those who suffer from it. Keep on reading to know how.
A Possible Solution for Flicker
LED LCDs use PWM. With LEDs, working with 100% duty cycle, no flicker is produced. Some LED backlit
LCDs operate at 100% duty cycle when the brightness in the monitor's menu is set to 100%. This is
how we can get an other possible solution to the problem of flicker in monitors.
In other words, some LED backlit LCDs completely stop flickering (like my Incandescent LCD) when the
brightness setting is set to the maximum level. Of course the screen will become too bright for
comfort with the maximum brightness setting, so lowering the overall brightness by lowering the RGB
settings, contrast is recommended. You can also lower the brightness in your graphic card's
settings. This brightness setting should not affect PWM. As long as you keep the brightness option
in the monitor's menu at maximum, you can lower any other setting and it won't affect flicker. And
if it turns out that the screen still uses PWM at full brightness, it is still better to use the LCD
that way, because of the shorter off periods. On some standard LCDs I used to get no headaches when
using them at full brightness, on others the headaches just become less when compared to low
When I tried my first LED LCD, I was not fully aware of this and my eyes were also very sensitive to
light. This made me lower the brightness setting and every other setting as well. The result was
that I couldn't use the monitor and had to return it. If I had set the brightness correctly and used
sunglasses or a tinted anti-glare screen, maybe my eyes would have accepted the LED monitor. And
since CCFL LCDs use the same pulse-width modulation, some of them may have no flicker at full
brightness as well.
I remember a Dell monitor I had when my eyes were only starting to hurt from LCDs. As a solution to
my eye pain I tried using sunglasses. But when I put them on, the brightness of the LCD became too
weak so I set it to maximum. And for a few days I was convinced that sunglasses were the solution to
the eye pain. Later I thought I'd reduce the brightness a bit and then my eyes started hurting
again. I never knew until now why I was problem free those few days with the sunglasses. Now I found
out. It had nothing to do with the sunglasses themselves, but everything to do with setting the
brightness to maximum and stopping the flicker. I tried maximum brightness on other monitors later,
but had no success in regard to the eye pain. The Dell was a special one, having no flicker at full
brightness. Too bad I gave it away before realizing it.
So not all LED backlit LCD monitors will have zero flicker at maximum brightness/ backlight (if the
the display has the option "backlight" in the menu, then it needs to be maximized instead of
brightness).Some continue flickering at very high frequencies and are useless for people with health
conditions similar to mine. Some probably do stop flickering completely, but I suspect that as time
goes by there are more being manufactured with flicker at 100% brightness then without, but I can't
know for sure. If you have an opportunity to try an LED or CCFL backlit LCD, then try it with full
brightness. If it's set only a tiny bit under the maximum level, it can turn out that you can't use
it, but if the settings are fully maximized, it might be the best monitor of your life.
PWM Controlled CCFL LCDs
It has come to my attention at a certain time that not only LED LCDs but also CCFL LCDs may use
Pulse-Width Modulation. There are two ways of dimming the CCFL backlight - analog and digital (PWM).
The analog dimming is used less and less in today's LCDs because of the quite poor dimming range.
The PWM dimming is becoming the dimming technique of choice since it offers more flexibility in
choosing brightness levels. While with analog dimming the brightness could be only lowered to 30% -
50% of the maximum brightness of the CCFL, using PWM the brightness can be reduced to about 1% of
the maximum of the lamp's brightness. The bad news is that PWM controlled CCFLs usually operate at
low frequencies, usually below 200 Hz, and the time that the light spends in the off state becomes
longer the more brightness it reduced. Here are some quotes:
"CCFL backlights do flicker, though. If a CCFL
LCD monitor is set at 100% brightness, it probably flickers in the 10,000 to 20,000Hz range and is
not an issue. But when using a PWM switch to reduce brightness, some monitors can get below 200Hz,
at which point those sensitive to flicker may begin to feel the effects. "
"CCFL brightness is controlled pulse width
modulation (PWM) dimming wherein the lamps are pulsed at a low frequency, typically 100 Hz to 200
Hz, and the duty cycle for each cycle varies from zero to 100%. A duty cycle of 50% then will
provide display brightness approximately half that provided at a duty cycle of 100%."
Many with the
LCD problem are usually sensitive to light and lower the brightness instantly as they get an LCD. By
doing this they are creating worse flicker and suffer more unknowingly. I have always lowered the
brightness on my CCFL LCDs and always felt eye pain. Part of the reason for my eye pain with CCFL
backlit LCDs was that I always used the monitors with a low duty cycle (the percentage that the
light is on compared to the time that it's off at a certain fixed frequency) and a low PWM
frequency. My ViewSonic also had PWM. I could see it by using the "pencil test". The test involves
waving a pencil very fast in front of the screen with the brightness of the LCD lowered to it's
minimum. LCD monitors with PWM regulate the duty cycle of the PWM by the brightness setting. When an
LCD has the backlight option in it's menu, then the duty cycle of the PWM is controlled by the
"backlight" setting instead of brightness. By lowering the brightness or the backlight, depending on
what monitor you have, and waving with your pencil in front of the screen you should see a
sctroboscopic effect, that isn't present in light without flicker or in light with very fast
flicker. By seeing the stroboscopic effect on your CCFL LCD with the completely reduced
brightness/backlight setting and not seeing it at maximum brightness/backlight you know that your
CCFL LCD uses digital PWM dimming. The flicker becomes visible with the pencil test. I even see the
flicker in my plasma TV (that I don't watch) by only using a pencil.
Monitors Without Flicker
Here are the monitors that have no PWM or a high PWM frequency. There is a high chance that if you
buy a monitor from this list that it will truly be flicker-free, with no subliminal flicker. But
there has been a case with a refurbished LCD that was from the list, but most probably had flicker
when one user bought it. So there's no guarantee that you will be helped, but there is a very high
probability that you will. Most of the LCDs below have a small grid, so most of them should make a
tremendous difference if you compare them to regular LCDs.
1) LG L1942PK
This monitor was tried by a computer user on the guestbook and the user says that it causes him no
eye pain. He has tried many monitors and only this one causes him no problems. I assume that it has
no flicker and that is the reason why this LCD is OK for him. It might have analogue dimming or a
very high PWM frequency. It has a pixel density (PPI) of 86.27. This pixel density seems too low for
comfort, but the absence of PWM seems to be enough for the user to have no problems with it. The
pixel density indicates how big the grid is. The bigger the Pixel Per Inch value, the smaller the
grid and the less problems it will cause.
2) HP ZR2740W
The German website prad.de has tested this LCD which uses no PWM at any brightness. It has a pixel
density of 108.79. The higher the pixel density, the better and this one is really high.
3) HP ZR2440W
The LCD HP ZR2440W is measured to have a PWM frequency of 430 Hz. This is high enough to not cause
any problems. It has a pixel density of 94.34, which is a good number. This monitor has been tried
by a user and it reduced the monitor symptoms greatly for him. So it's worth buying an unrefurbished
verion of this monitor.
4) HP L2035
The HP L2035 has no PWM at any brightness. But it hasn't helped a user on the guestbook. We both
assume that some of the HP L2035 LCDs have PWM while others don't. He bought it refurbished so
perhaps the non-PWM part was replaced with a PWM part while doing repairs on his specific HP L2035.
Non-refurbished HP L2035s may be OK. It has a pixel density of 99.5, which is a good one.
5) BenQ RL2450HT
The BenQ RL2450HT has a PWM frequency of 360 Hz. This is higher than the usual 200 Hz and is enough
to not cause any problems. Its pixel density is 91.79, which is OK. This LCD was tried by a person
and he says that it solved 80% of his symptoms. So the size of the grid of 91.79 density is only
causing 20% of the problems. A smaller grid would cause even less. My Viewsonic has almost the same
pixel density and the grid caused me only some minor discomfort. I would say 87% of my symptoms were
gone when I changed the backlight to incandescent with no PWM.
6) Acer S243HLAbmii
The Acer S243HLAbmii has a PWM frequency of astonishing 510 Hz. It was measured by the German
website prad.de. This is by far higher than the usual 200 Hz and in people who only suffer from the
backlight's flicker it will definitely cause no problems. It has a pixel density of 91.79, an OK
7) LG Flatron M2382D-PZ
The LG Flatron M2382D-PZ has a PWM frequency of 300 Hz, measured by prad.de. 300 Hz is pretty low,
but it is possibly enough not to cause problems when used near full brightness. It has a pixel
density of 95.78, which is nice indeed.
8) Dell U2713HM
The Dell U2713HM is an LED LCD with no PWM brightness control. It was found to have no PWM by
tftcentral.co.uk. It has a pixel density of 108.79, which is very good, because it's very high. The
bigger the pixel density the smaller the grid between the pixels.
9) DGM IPS-2701WPH
It uses no PWM brightness control. It was found to have no PWM by tftcentral.co.uk. It has a pixel
density of 108.79, which is very good.
10) Samsung S27B970D
There are conflicting PWM measurements of this LCD. tftcentral.co.uk claims that it uses no PWM
brightness control, while prad.de says it has no PWM at full brightness, but 180 Hz PWM at lower
brightness. A person reading this site has bought the display and says he can only look at it when
it is set to 100% brightness with no PWM. So it turns out prad.de is right and the LCD uses PWM at
any brightness less than 100%. It has a pixel density of 108.79 which is very good.
11) Shimian QH270 -IPSMS
It is completely without PWM, measured by prad.de. It has a pixel density of 108.79, a very good
More monitors may be found on the internet. http://pcmonitorsguide.blogspot.com/2012/12/monitors-
with-no-pwm.html has some models not mentioned here. You might also want to research EIZO (EV2736W,
EV2436W, EV2416W, EV2336W, EV2316W) and BenQ (GW2760HS). The EIZOs seem to have no PWM is brightness
is set to above 20. They are also a more reliable purchase because, as far as I read, this PWM
information comes from the manufacturer directly.
You need to keep in mind when buying one of these monitors that the manufacturers may decide to
change the PWM frequencies of some monitors for whatever reasons. It seems that this has been the
case for the Samsung S27B970D mentioned above as well as for the HP L2035, although the HP was
refurbished and that was most probably the reason why it didn't solve the problems of its user. We
get stories about the same model of an LCD in the US being PWM-free, but using PWM in Europe. So by
no means does it mean that PWM is not a problem if you bought an LCD from the list and still
continued to have symptoms with it.
If you buy one of the listed above LCDs and it turns out that you can't use it, please try using it
with a non-native screen resolution, especially if you are a Mac or Windows 7/8 user. I will explain
why I think it will help if you continue reading.
If a non-native screen resolution in combination with a non-PWM LCD doesn't help as well, perhaps
your LCD is a 120 Hz LCD. The 120 Hz could be created by inserting black frames, which could create
flicker. If you suspect that this flicker is the reason for your symptoms if you have tried a PWM-
less LCD with an unnative screen resolution, then please try setting the LCD to 60 Hz. This might
If nothing I suggested helped, plese try lowering the brightness of the LCD to minimum, opening some
white content on your computer, and waving with a pencil in front of the LCD in a dark room to see
if the LCD is really without PWM. If you see a stroboscopic effect (many pencils), then the monitor
uses PWM and probably has a low frequency. Please check for PWM to be completely sure if it is there
or not to know if it is the problem. If the first LCD you bought from the list turned out to be with
PWM after all, I suggest not giving up and getting a second LCD without PWM if you really need an
LCD which won't cause you eye pain, headaches, dizziness, nausea etc.
A Solution for Apple and Windows 7 Users
Most of today's Apple products show no signs of flicker when being measured for PWM. Yet some users
report having severe symptoms, similar to PWM problems, without flicker being measurable. Someone
measured his LCD to have no flicker, but still had his symptoms with it, while he paradoxically had
almost no problems with an other LCD with PWM at 170 Hz. When the user tried a non-native screen
resolution, he found that his symptoms had 70% gone. Some users were fine with their LCDs until they
upgraded from Windows XP to Windows 7. So there is something going on with Windows 7 and Apple's
operating systems or the drivers that come along with them. Often, a non-native screen resolution is
a solution in such cases. I suspect that somehow the millions of pixels that the LCD screen is made
out of are very slightly flickering in a chaotic manner, like a snowing effect. The dept of the
flicker may be very low and because not all of the pixels of the screen turn off all at once, it is
not detectible via flicker detection methods. A non-native screen resolution might be causing the
information that is comming from the drivers to the monitor to get partially lost and
changed/deformed/converted and this way every distinct pixel might not be getting the correct
command of how it needs to flicker and doesn't flicker at all or much less pixels flicker as a
result of a non-native screen resolution. But this does not have to be the case. I'm just explaining
the evidence the best way I can. It has also been reported that someone has used Windows 7 with no
problems, but started having "flicker symptoms" when he upgraded to Windows 8. So one thing is for
sure - besides the PWM problem there is a new more powerful software problem emerging. The two
combined will cause much confusion in people searching for reasons of what causes eye pain,
headaches, dizziness, nausea and much more. And don't think that a non-native screen resolution will
always work if you have non-PWM LCD that is giving you problems. Just as using the LCD at full
brightness rarely solves the PWM problem, the same way a change in resolution may not always be
helpfull. So there are 3 problems I have found in LCDs that make it hard for people with weakened
nervous systems to work with: PWM, big pixels and a new software problem. If you are suffering from
this latter problem and know for a fact that your monitor has no PWM, and you are using Windows XP,
then you could try deleting your graphic card's drives and get stuck with the standard Windows
graphics driver that you have after you have just installed Windows XP and haven't yet installed the
correct graphics driver yet. I only recommend doing this if you know what you are doing and have
backed up setup files to at will be able to reinstall those deleted drivers. Newer Windows come
with drivers and force them upon you. Only XP has this "driverless" state of the graphics drivers.
Also, you might want to try many resolutions, however none of them will help if you still have the
PWM problem. It is becoming tricky nowadays to figure this stuff out since new problems keep
appearing. I only know about this software problem from forums. Removing PWMated light and placing
incandescent light has worked very well for me so far.
The Surest Solution for Flicker
I see more and more sources saying that the frequency of the PWM in CCFL and LED backlit LCDs is
roughly around 200 HZ. In some cases it is slightly higher and in other cases lower. This 200 Hz
number is also the approximate number of Hz of flickering light that the human nervous system can
subliminally detect according to latest studies. Also, it seems that the backlight only in very rare
cases turns the PWM off at the full brightness setting on the monitor. No matter what we do, we have
this 200 Hz flicker in LED and CCFL backlit LCDs. Here is a quote to show you what I mean:
"The electronic ballasts in CCFL backlights may run at 40,000Hz or so, but the PWM used for dimming
"only runs at about 175Hz and is visible to some people. I've tested several displays using a
"photoresistor and all cycle between 175 and 220Hz.
LED backlights can be dimmed by adjusting their current, but this is usually not done for bright
backlight LEDs because this can cause color shifts and other problems. This leaves PWM as the only
real means of dimming the display, and appears to work at the same frequency as CCFLs (though I have
not measured it directly). Effects from a small duty cycle can be worse with LEDs because they do
not continue to glow for several milliseconds like CCFLs when switched off." What is the solution to
this ~200 Hz problem that is on the edge of our subconscious perception? Increase the frequency! If
you're really tired of the eye pain and want to stop your nervous system getting damaged by the
flicker, take your LCD with a small grid to a place where you would take it if you needed it
repaired and ask the repairman if he can set a much higher frequency on the PWM than 200 Hz. The
higher, the better! 350 Hz has been shown to not cause problems in one person who has tried it. I
know that setting a higher PWM frequency is possible having it proposed to me by a person that
repairs these things.
All pieces of the puzzle fit wonderfully together with this explanation.
It is viewed as impossible that a high enough frequency, such as 5 kHz, can be perceived
subliminally. It would not even come into mind to people who study light. There have been studies
made and the result of one of them should show a number much higher than 200 Hz if it was possible
to perceive, let's say, 600 Hz. And indeed, I have tried a fluorescent lamp with an electronic
ballast, that is with flicker in the kHz range, and had no trouble.
"My wife's friend with no persistence of vision agrees. She says that there is no picture on the
"screen, just flashes of light.
Does your wife's friend see a picture on any of the types of TVs ? Plasma, LCD, DLP, 3 chip DLPs at
some movie theaters for the ads. I assume the home type color wheel DLP would look like rainbow
flashing to the friend. Just curious.
G² Essentially she can't watch any "normal" scanned display, she can see a picture on an LCD but
the blinking CFL will cause her to have a seizure (not fun). Anything that blinks like a DLP or a
projected movie causes seizures, anything that scans slowly enough like a CRT, she can't see an
image. She can see E-Ink electrophoretic displays perfectly (Amazon and Sony readers).
She can't see an image on a plasma which she says looks like colored flashes of snow on an old TV
(she was in her 30's when she had the accident).
She has not (to my knowledge) seen an OLED nor a 3-chip DLP. I suspect a current drive OLED and not
a PWM drive one would work for her, but outside of corporate labs, I have not seen a current drive
OLED (they are beautiful).
Her university had a special DC incandescent backlit LCD made so she could see the image of a
computer still display for her work (she is a scientist)... she still can't watch video or movies as
the frame rate causes siezures. Stores are off-limits, since most have HID or fluorescent lighting.
I found out about DC LCD from some work done at MIT on developing video for parrots, who apparently
have the same "problem", although in parrots it's the normal way they see. I don't know if other
birds have this ultrafast vision, I suspect it would be handy for flying in close foliage.
I also don't know how it has affected her ability to "see" optical illusions. Would probably be
interesting, though it seems that a lot of things can make her sick when she see's them, so who
wants to experiment.
The brain is a powerful processor which we take for granted."
Vasya's comment: If this person can consciously perceive the high frequency flicker of the
LCD's CCFL backlight, isn't it completely possible that other people can be affected by
the flicker unconsciously?
"An increasing number of people in Sweden are claiming that they are hypersensitive to electricity.
These patients suffer from skin as well as neurological symptoms when they are near computer
monitors, fluorescent tubes, or other electrical appliances. Provocation studies with
electromagnetic fields emitted from these appliances have, with only one exception, all been
negative, indicating that there are other factors in the office environment that can effect the
autonomic and/or central nervous system, resulting in the symptoms reported.
Flickering light is one such factor and was therefore chosen as the exposure
parameter in this study. Ten patients complaining of electrical hypersensitivity and the same
number of healthy voluntary control subjects were exposed to amplitude-modulated light. The
sensitivity of the brain to this type of visual stimulation was tested by means of objective
electrophysiological methods such as electroretinography and visual evoked potential. A higher
amplitude of brain cortical responses at all frequencies of stimulation was found when comparing
patients with the control subjects, whereas no differences in retinal responses were revealed."
"Common ailments associated with flickering, according to the Occupational Safety and Health
Administration (OSHA), include “headaches, eye strain and general eye discomfort.” In fact, a study
published by Lighting Research and Technology in 1989 found that exposing workers to lights without
flickering “resulted in more than a 50 percent drop in complaints of eye strain and headaches.”
"I had a similar problem years ago - blurry / itchy watery eyes :( went to a eye specialist but he
"could not find anything wrong with my eyes - no infections - no nothing!! Even stopped wearing
"contact lenses, but still had the problem. then I discovered what was causing it. the CFL light
"behind my Sansui 54cm CRT TV. When ESKUM was still bullsitting us with rolling black outs, I bought
"a 105amp sealed battery & 700w inverter to power the tv / pvr & a CFL light. When the rolling black
"outs stopped, I stopped using the CFL light and my eye problem stopped. So I tested this and yes
"again after watching tv with the CFL light on behind the tv I got the symptoms again! Now obviously
"I don't stare at the actual CFL light, its behind the tv so I only get the glow of the light from
"the white walls around the tv, but if I spend to much time in front of my samsung 226BW LCD screen
"or watch tv in my bedroom on my samsung 2370 LCD I get the same symptoms :( from what I understand
"about LCD screens is that they r back lit with florescent lights? CCFL or HCFL fluorescent lamps.
perhaps the new LED LCD's will solve this problem?? but at R25k - R60k a bit to expensive to
experiment with :("
Vasya's comment: This person is obviously more affected by the higher flicker
frequency of the fluorescent light in the background than the lower frequency of flicker of his CRT.
The same goes for his LCD's backlight.
"Health Hazards of Fluorescent Lighting
Known effects and their likely causes
The following is a list of symptoms and diseases known to be linked to exposure to fluorescent
Headache, eyestrain, eye irritation, fatigue, difficulty in concentration, increased rate of
‘misjudgments’ and accidents, malaise and irritability can be caused by noise, glare and flicker
from fluorescent lighting.
Increased stress (which may in turn lead to heart disease) can arise from increasing the intensity
of artificial light with fluorescent tubes. It has been shown that increased use of artificial light
(rather than natural light) affects the levels of hormones in the body, particularly the hormones
associated with stress, such as cortisol.
Variation in brightness, as provided by daylight, is necessary for the normal functioning of the
body’s rhythms. The monotonous illumination of fluorescent lighting may also add to the changes in
Allergic skin reactions and dermatitis can be caused by exposure to fluorescent lights. An unknown
number of people suffer from ‘cutaneous light sensitivity’ due to fluorescent lights. This means
that not only can they become allergic to fluorescent lighting but they can become more sensitive to
Certain long-term, mild skin diseases can become worse if the sufferer is exposed to fluorescent
light. Some medical drugs (including some tranquilizers, antibiotics, heart drugs and diuretics) can
make you particularly sensitive to UV radiation (photosensitivity). Skin eruptions then occur even
with the small doses of UV (in the 300-320nm wavelength range) emitted by white fluorescent lights.
Hyperactivity has been linked to the flickering produced by fluorescent lighting. Microwave
emissions from fluorescent lighting are also suspected of contributing to these behavioral
disorders. Other mild behavioral disorders in children may be made worse by working at school under
There is also some evidence that the following effects may be caused by exposure to fluorescent
Increased risk of seizure in epilepsy sufferers
Higher incidence of miscarriage
Speeding up the aging of the retina. More health problems to fill their pockets."
Vasya's comment: If you'll follow this link, you will find the most incredible accounts of how fluorescent lights can
"One of the problems with alternating current (AC) is that when it is used to power electric lights,
"the light intensity fluctuates in synchrony with it, at twice the AC rate: 100 times per second in
"a 50 Hz power system (as in Europe and Australia) and 120 times per second in a 60 Hz system (as in
"North America). In incandescent lamps, this modulation is fairly small because of the tungsten
"filament that keeps glowing between pulses; but in FL tubes powered by conventional magnetic
"ballasts, the variations are much bigger, resulting in continual flicker. This flicker is not seen
"by the eye until it slows down towards the end of the tube's lifespan, but may nevertheless be
"perceived subliminally by the body and the brain.
In a study on healthy people of various ages, Kueller &, Laike (1998) at the Lund Institute of
Technology found that even though subjects couldn't actually see the flicker, many still preferred
the non-flickering light source, and that about 40%, mostly younger and less addicted to alcohol and
nicotine (indicating a more alert, nervous system not dulled by age or intoxication), were more
sensitive to flicker and reacted with decreased alpha brain-wave activity, increased speed and more
errors in performance.  They also mention other studies - such as the ones by Wilkins et al
(1989), linking flicker from FL to headache, eye strain and general stress ; by
Colman et al (1976), finding that autistic children became more distracted and stuck in repetitive
behaviour (a sign of stress or trance) under FL than under incandescent light; and by
Zaccaria & Bitterman (1952), whose subjects preferred FL tubes powered by DC to those powered by AC."
"LED brake lights and cheaper LED flashlights use low frequency pulse width modulation techniques
"for dimming. When these lights are not lit to full brightness, they will flicker at rates that can
"make some people nauseous. The effects are similar to staring at an CRT monitor (or TV) with a very
"low refresh rate. It is the flickering that is the issue, not LED light per say.
If you are sensitive to low frequency flickering and you wind up with a LED backlight that uses low
frequency PWM to control screen brightness, you will have problems when the screen is not at full
brightness. You might be able to avoid the problem by running the screen at full brightness, but
there's no assurance that the backlight dimmer will run the LEDs constantly even at full brightness.
There are ways to dim LEDs without inducing nausea in a percentage of the population, but device
manufacturers are seldom prepared to spend the money."
"Having looked over that thread I'd say the issue is the psychotropic effects of flicker acting
through the visual system. Certain flicker rates can have profound effects on people--altered moods,
migraine headaches, or even epileptic seizures--and the Macbook effects are in line with this."
"There is good evidence that fluctuations in the light signal are detected by
the nervous system up to perhaps 200 Hz"
Vasya's comment: It is likely that the number is either slightly or much higher
and it also depends on the depth of modulation.
"Different points in the visual system have very different critical flicker fusion rate (CFF)
sensitivities. Each cell type integrates signals differently. For example, photoreceptors are very
slow and sluggish whereas some retinal ganglion cells can maintain firing rates up to 250 Hz."
"The issue of LED flicker came to the fore recently, after the Energy Star criteria for Integral LED
Lamps included a requirement for LED operating frequency to exceed 150 Hz. It is now proposed to
change this requirement back to 120 Hz."
Vasya's comment: The Energy Star criteria for Integral LED
Lamps should include a requirement for LEDs to have no flicker frequency at all to ensure that every
one can be near such lamps without having possible health problems. I do not suggest making lamps
that don't produce light, but what I mean is that the LEDs should always have no visible or
invisible flicker while shining.
"Flicker frequencies - whether perceived consciously or not - have a negative impact on the eyes,
brain, brain waves, hormones, nervousness, neurological processing, regulation and control centers,
coordination, metabolism, glucose consumption, capillary blood flow or sleep quality. They can also
trigger migraines, headaches or epileptic seizures." So says Dr. Christin Steigerwald in her
doctoral thesis at Ludwig Maximilian University in Munich.
"My belief is that the symptoms of electrical sensitivity are primarily due to a severely weakened
nervous system being overloaded by electromagnetic fields. Therefore, strengthening the nervous
system is of paramount importance in order to heal this illness."
Vasya's comment: I believe that
this problem with monitors (that occurs mostly when one ruins his health with flickering CCFL
backlit LCDs or LED LCDs) is part of electrical sensitivity and is curable the same way as
electrical sensitivity is - by healing the nervous system. I recommend reading this website, for as
different the symptoms of the site's owner and the victim's of flickering monitors may seem, the
reasons for them are the same. By knowing the reasons for our illnesses, we can start thinking about
ways to heal our-selfs.
Do You Have What I Have?
You might not be sure if you have the same problem as I have. Maybe because your symptoms are a bit
There is one relatively easy way to find out. Answer these questions:
"Do you have the same symptoms, but maybe less intense, when you are near fluorescent lamps in
"places like supermarkets?
"Do you have eye pain and the ophthalmologist cannot detect anything wrong with your eyes?
"Do eye drops not help you with your eye pain?
"Do you get symptoms from LCDs, CRTs, LEDs or projectors?
"Do you only get your symptoms from monitors and fluorescent light?
If you answered the questions with yes, then the probability that you have what I have is very high.
The more you answered with yes, the more probable it is that you have what I have.
If you aren't sensitive to fluorescent lights, but nonetheless suffer from LCDs, perhaps it is the
grid between the pixels that is causing you your problems. Perhaps the grid alone or the grid
combined with the flicker of the backlight. Try using a CRT and see if you can use it, for it hasn't
such a grid between the pixels as LCDs have.
Another indication that we share the same problem would be if your eyes hurt after using the LCD and
they would stop hurting during the time that you eat or do physical work, but start hurting again
when you finished your meal and stopped working. It happened to me, but I'm not sure how reliable
this question is in finding out if you have the same that I have.
The info on this site comes from personal experience of experimenting, as well as from pondering
about the problem and reading a lot of material on the Internet. Evaluate it and use it for your