Try two bulbs with different flicker at the same time and see if it worse than two of the same. Sure seems like having things at different hz here is a surefire way to induce symptoms. Even having two different monitors with different refresh rates does. Like having the TV far way running behind the laptop.

Maybe many of the issues are simply a timing issue in the brain, and adapting to it?

Fair question, does anyone have screen sensitivity while outside? When the environment is brighter than the screen, and there are no artificial light (or sound). Would be interesting to hear from someone that has significant issues test a monitor outside. However would preferably be without highly dynamic refresh rate like ProMotion or VSync.

Would also be interesting to hear if anyone experimented with music with a fixed beat, binaural beats or similar.

Some proposed mechanisms from from ChatGPT.

The potential discomfort caused by using two monitors with different refresh rates may indeed be rooted in neurological mechanisms, including the way neurons process temporal information. Here's a more in-depth exploration of the neurological basis:

  1. Temporal Integration and Neuronal Adaptation:

    • Neurons in the visual system integrate visual information over time. When presented with stimuli at different temporal frequencies (i.e., from monitors with different refresh rates), these neurons might continually adjust their firing rates to adapt.
    • For instance, certain retinal ganglion cells respond preferentially to temporal changes in light intensity. When visual input flickers (as in a lower refresh rate monitor or inconsistent refresh rates), these cells can increase their firing rate, potentially leading to a heightened sense of discomfort or visual fatigue.

  2. Visual Pathway Overstimulation:

    • Neurons communicate using electrochemical signals, and a consistent or predictable rate of stimulation allows for regular periods of activity and rest. Inconsistent temporal input, such as switching between screens with different refresh rates, might result in irregular neuronal firing patterns.

    • This irregularity can potentially lead to overstimulation or "overwork" of certain pathways, which might manifest as eye strain, headaches, or even migraines in sensitive individuals.

  3. Cortical Processing and Attention:

    • The primary visual cortex and higher cortical areas responsible for attention and object recognition might experience increased demands when processing differing temporal inputs simultaneously.

    • This increased demand might lead to a sensation of "mental fatigue" or difficulty in concentrating, especially during tasks that require shifting attention between the two screens frequently.

  4. Mismatched Multisensory Integration:

    • If one is using both screens for a task that involves motion and sound (e.g., video editing), there might be a mismatch in how the brain integrates visual and auditory information due to the difference in refresh rates.

    • The brain is adept at synchronizing visual and auditory cues, but discrepancies introduced by differing refresh rates might pose challenges in this multisensory integration process, potentially leading to discomfort or disorientation.

  5. Interhemispheric Communication:

    • Visual input from each eye is processed in both hemispheres of the brain. If each eye is predominately focused on a different monitor (left eye on the left monitor and right eye on the right monitor), and each monitor has a different refresh rate, it might introduce disparities in the visual information processed in each hemisphere.

    • Efficient interhemispheric communication is crucial for unified visual perception. Disparities in temporal processing might pose challenges to this communication, leading to potential visual discomfort.

Or just take an extension cord and bring out your worst bulb. See if it is problematic outside.

jen thanks @jen. Are the Phillips model 9290002268 still the best LED for you? Unfortunately in USA the incandescent / halogens have been banned, however, appliance incandescent (like for an oven) should still work in a regular lamp. I've heard good things about Avulux / Axon glasses too.

  • jen replied to this.

      Yeah, oven bulbs are 40w but make sure you don't get one that is 130v, otherwise subtract 25% from the lumens.

      ryans Are the Phillips model 9290002268 still the best LED for you?

      Maybe…I only have them in one ceiling fixture, though, and I don’t want to move them because their housing has cracked, so I haven’t been able to test them for constant use. Their flicker pattern is very different than any of the other low flicker LEDs that hurt me, and I’ve never been noticeably hurt the least bit by them in 10 years of daily use, so as far as I can tell, they’re good. I’m still using new-ish Waveform bulbs some time of the time and they seem ok, but I’m periodically checking their flicker with a meter. I’m still experimenting to try to figure out what’s the least harmful AC bulb option for me, whether incandescent or something else - and using sunlight, candles, or constant DC LEDs whenever possible since none of those hurt me and sunlight and candlelight seem to possibly help.

          jen Thanks @jen. I hope you can find a suitable bulb soon. I wonder if someone with knowledge of electrical engineering could design a "DC Lamp" that only provided direct current to any bulb? Then, flicker would no longer become a problem?

          There are some new migraine medications (like Ajovy) I wonder if they can help us.

            5 months later

            Hi everyone,

            Please check out my data correlating light and screen flicker with my concussion-like health symptoms posted here: https://www.flickersense.org/testing-leds-and-screens

            I bought a professional UPRTek meter and have tested hundreds of light bulbs (dozens of kinds at least). I used this meter on screens too, but ended up also using microscopes and slow-motion video to quantify screen flicker better in 2 dimensions.

            My basic conclusions are that for me, flicker is bad, color-to-color-flicker is much worse, and with limited data, there's a hint that randomness in flicker might reduce harm from flicker.

            It turns out that the "good" Phillips LEDs I've used without harm since 2013 have 1% flicker, no color-to-color flicker, and happen to be in a fixture with a slightly unstable electrical supply that adds a little randomness to the flicker. So it's possible it's that randomness, rather than the bulbs themselves that makes them OK for me. Except for these Philips bulbs, I'm back to using incandescents at home.

            All the screens I tested have significant flicker, especially at the subpixel level. It turns out that all of my screens flicker the red, green, and blue subpixels in order to decrease color saturation - so the amount of flicker varies for different colors. This happens at 15 Hz, 30 Hz, or 60 Hz depending on the screen. The 15 Hz LCD screen seems much more harmful to me than 30 Hz LCD screens. It's worse for me when there's more subpixel flicker and especially bad when the red, blue, and green flicker don't track with each other, creating color-to-color flicker.

            Every screen I tested does something different with flicker, so it doesn't surprise me at all that sometimes those of us on this forum experience different things with different screens and it's hard to figure out general trends. Although one trend is that on all of my Apple devices, Nightshift works by adding somewhat more green and a lot more blue subpixel flicker, thus reducing the green-blue light. Now I know why my brain gets especially injured by Nightshift!...Why does Apple do this??

              jen thanks for all your info about this and the website. Super helpful. I'd say my symptoms and triggers are 1:1 with you. The Xiaomi 13T is the only phone I can use that doesn't give me the concussion symptoms to the severity like my old iPhone 11/SE 2nd.

                  jordan It's just that Xiaomi 13T (from $700) PWM 2880Hz at 100% brightness. Against 240Hz on new iPhone. My Infinix NOTE 30 VIP (for $300) PWM 1920Hz also good. I can watch YouTube videos for many hours. Soon such "good screens" can be bought from $200

                    7 months later

                    The Illuminating Engineering Society (IES) has a new draft proposal for recommendations on LED light flicker (TLM) limits - a proposed update to the 2015 IEEE 1789 and other similar recommendations for limits on flicker in architectural lighting. It's currently open for public review though August 12, 2024. I just submitted several dozen comments proposing revisions. Participating in the review process means that I agreed not to distribute the proposal in its draft form (so can't share its details), but here's the process if any of you would like to comment too. They charge $25 - I asked if there was any way for people injured by LEDs to participate in the review without paying the fee (since it seems wrong to me), but got no reply on that.

                    So in case you'd like to participate too, what I had to do was:

                    1. Go to https://www.ies.org/standards/ansi-standards-information/ and email the people listed toward the end of the page to ask to participate in the review of this Technical Memorandum:

                    "ANSI Standards: Open for public review
                    The following draft is available for ANSI Public Review comment Jun 28 – Aug 12, 2024:

                    BSR/IES TM-39 Technical Memorandum: Quantification and Specification of Flicker

                    This Technical Memorandum (TM) catalogs currently documented metrics and specification criteria related to the human perception of TLM, summarizes existing research, and identifies a path toward an IES standard method for quantifying and specifying flicker for architectural lighting. It excludes information regarding the effect of flicker on plants and animals. It also excludes information related to the measurement of TLM, which is covered in ANSI/IES LM-90-20."

                    1. They will reply with another link for you to purchase a copy for $25 and a description of the terms of participation. At that point I got stuck and had to contact them again to figure out that I had to create an account first before I could checkout using this link: https://idp.ies.org/Account/Login

                    2. After paying, they'll send another email with the document for review, a form for recording comments, and more submission directions.

                    I attempted to represent not only my own experience and data collection, but also what I've learned from others on the forum and others who I know in real life who are also experiencing health effects from LEDs.

                    jen

                    Your mentioning of the 15 Hz frequency reminds me of flicker vertigo and strobe lights but in our situation it is rgb subpixels:

                    https://en.wikipedia.org/wiki/Flicker_vertigo

                    Flicker vertigo, sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light."[1] It is a disorientation-, vertigo-, and nausea-inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves.[2][3] The effects are similar to seizures caused by epilepsy (in particular photosensitive epilepsy), but are not restricted to people with histories of epilepsy.

                    • jen replied to this.

                        photon78s Yes, I agree - I think it's likely that flickering the screen subpixels at frequencies that are known to trigger severe neurological issues with architectural lighting could be a significant reason why many of us are harmed by screens. The subpixels can be large enough to be just barely individually visible, especially within something narrow, like a line in a text character. Even without obvious temporal dithering effects, the subpixel flicker seems to be bad for me, but the newer devices that are very likely to be adding temporal dithering seem to be even worse. Whether someone's symptoms are more similar to dry eye/eyestrain or migraine or concussion, or some mixture of those, all of the symptoms can have neurological causes, perhaps with some kind of light-triggered inflammation being part of the story too.

                        The research literature on digital eye strain/ computer vision syndrome has grown significantly since Covid, with clear links between more screen use and more symptoms in adults and children. The meta-analyses of survey data estimate the overall prevalence to be ~65% of people with suggestions of less screen time and more breaks being the only really helpful interventions (with little to no evidence for blue-blocking lenses being helpful). However, the optometrists and ophthalmologists are still only talking about eyes being tired/fatigued as the cause. They haven't started to really consider the issue of screen flicker. I suspect that part of the problem is that it isn't something they can fix with lenses or easily measure or change, so even if they think of it, it would be hard for them to study. I certainly don't believe that my eyes can get so tired within seconds that pressure builds in my temple and other concussion-like symptoms start. It seems that many of us similarly can have symptoms start within seconds, so I don't understand at all how "fatigue" could be the main problem. Years ago when I would just start to get minor headaches after hours on a computer, I might have been more receptive to the "fatigue" hypothesis, but not now. We need real research so badly...

                            jen However, the optometrists and ophthalmologists are still only talking about eyes being tired/fatigued as the cause

                            The closest I've seen conventional doctors not specializing in this area of research relate to is the not dissimilar problem of photosensitive epilepsy.

                              jen

                              This link is about a "low emissions computer" project relating to EMF sensitivity not specifically LED flicker. They use incandescent light for the display and a rear projection system. What I find also interesting is that it was funded by US Department of Education and the National Institute on Disability, Independent Living, and Rehabilitation Research.

                              http://asilo.com/aztap1/

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