Demographic statistics and relevant medical history:
Female, living in New York City
Highest level of education: PhD in Human Genetics and Molecular Biology.
Employed full-time in science education. My current job is low-stress.
No history of concussion.
No history of sleep issues.
No anxiety or any mental health issue.
No history of eye problems other than nearsightedness.
History of common migraine without aura.
Following the onset of LED symptoms in 2018, I consulted a neurologist who did an MRI, a neuro-ophthalmologist who did extensive tests of my eyes, and an optometrist. None of these experts detected any problem, except that the neuro-ophthalmologist detected peripheral blindness in my right eye in a visual field test during my first visit when the clinic LED lights triggered my symptoms, but did not detect it on a followup visit where I protected my eyes from the clinic LED lights. The neurologist did various tests of neurological function that did not detect any issues, but I had to wait so many months for an appointment, that I wasn't experiencing LED symptoms (except enhanced sensitivity to flicker) by the time I had the appointment.
Comparison of my common migraine symptoms and my LED-caused symptoms
Onset and frequency of occurrence
Common migraine without aura: First onset at age 13 and at that time occurring repeatedly for several weeks. Since then occurring a few times a year (with unknown triggers) for less than a day each time, but can usually be stopped early with ibuprofen taken at symptom onset. Typically lasts about 6 hours if untreated. Often feel tired for about another 24 hours.
LED symptoms: First onset at age 42 in 2018. Repeatedly re-exposed to flickering LED lights (overhead LED strip lights covered by a diffuser that had ~1000 Hz flicker with a very subtle flicker percent, 0.7%) that triggered symptoms at my place of employment over multiple months (Sept. - Nov.) with symptoms occurring every day of exposure. Symptoms increased in severity over this time period. There was a slight reduction in symptoms over the course of each weekend, with relapse in severity upon returning to work each Monday. Some symptoms lasted for days, some for weeks, and some for months after I became able to significantly limit exposure to the triggering lights in late November 2018 (ongoing building construction reached the point that the lights could be controlled by wall switches rather than constantly being on). Symptoms had mostly abated by the late spring of 2019, with the exception of enhanced sensitivity to flickering LED lights and LED screen use compared to prior to symptom onset. A 45 minute exposure to triggering LED light flicker at the newly-remodeled office of a neuro-ophthalmologist in January 2019 triggered new symptoms with headache lasting 8 days. Since then, minor exposures to flickering LED lights and screens would mostly trigger symptoms lasting from hours to days, depending on the severity of exposure. "Minor" exposures include any time I had to use a computer or device screen for more than a few minutes and any time I looked at a Zoom video feed for a few seconds. A major exposure to flickering LED lights occurred in April 2021 when I spent 3 hours in a newly-remodeled building with triggering LED lights. This exposure has triggered ongoing symptoms, some of which have lasted months (Timeline of 2021 "LED" Symptoms). I am still, in Decmber 2021, not back to the baseline sensitivity I had prior to this exposure. I now experience at least new minor symptoms almost every day, as it is now impossible to avoid exposure to triggering LED flicker in most NYC environments. I don't have a way to use a computer without triggering symptoms, so I keep getting new symptoms every time I work on this survey or website.
Location of headache:
Common migraine without aura: Left side only: top of forehead.
LED symptoms: Right side only: behind eye, in tissue near the eye toward the temple, and temple.
Quality of headache:
Common migraine without aura: Pulsing in time with heart beat.
LED symptoms: Feeling of constant pressure and dull, constant pain behind right eye, near eye, and in temple. It feels like the tissue inside my head is swollen and the brain tissue is pressing outward. There is not a pulsing quality and It does not feel like there is a band pressing around the head.
In addition to the above headache pain/pressure that can last days to months after a significant LED exposure, there is also a sharper, more localized pain behind my right eye that is only present when I can actually see LED light or other flickering light. It stops immediately if the light is turned off. The intensity of this pain and the time until this pain starts once I am exposed to flickering light depends on my sensitivity level and on the intensity of the flicker, with time until pain onset ranging from immediate up to at most 20 minutes. I'm more sensitive and the pain starts faster and is more intense if I've recently been exposed to flickering light or have ongoing symptoms from a previous exposure. This pain was the most intense in the fall of 2018 - it kept getting more intense each work day while working under the flickering LED lights. When very intense, it had a very high-frequency vibrating quality on the order of hundreds to thousands of hertz. It felt like a dentist's drill was creating vibrating pain/pressure behind my eye. At that time, the sharp vibrating pain would start immediately when I entered the flickering LED light and would stop immediately if I left the flickering LED light. This pain was sharp like the feeling of lemon juice in a paper cut, and seemed somewhat distracting, but wasn't debilitating in the way that common migraine headache pain is debilitating for me.
Headache pain intensity
Common migraine without aura: Severe - debilitating; can't do any normal activities.
LED symptoms: Varies from mild to moderate, depending on severity of LED exposure. Can almost always push through the pain, disorientation, and nausea to attempt to do normal activities, but with significantly compromised short-term memory, concentration, spatial orientation, appetite, and sleep.
Is the headache aggravated by routine physical activity?
Common migraine without aura: Yes. To the point that I need to sit or lie down and not move at all while I wait for ibuprofen to take effect or for the migraine to end on its own. Movement intensifies the headache and movement significantly intensifies the nausea and feeling of vertigo.
LED symptoms: No. Moderate exercise has absolutely no effect on the headache or other symptoms. I walk multiple miles each day, even when experiencing LED symptoms.
Is there nausea or vomiting?
Common migraine without aura: If untreated, or if treatment with ibuprofen doesn't happen quickly enough, there is always nausea, usually with a spinning vertigo sensation, that builds in intensity until vomiting. Nose runs and headache pain becomes very severe prior to vomiting. The nausea and the migraine headache tend to end immediately after vomiting, after which fatigue is intense and I fall asleep.
LED symptoms: There is nausea, but it never leads to vomiting. Almost always, flickering LEDs trigger a mild feeling of spatial disorientation only when actually looking at the LEDs. Sometimes flickering LEDs or repetitive patterns trigger a more intense feeling of spatial disorientation and moderate nausea only when looking at the LED light or at the patterns. If an LED exposure has been significant enough to trigger symptoms lasting hours or longer, ongoing symptoms that are still present even after the end of the LED exposure often include nausea and spatial disorientation. The nausea can vary from mild to moderate and tends to include a loss of appetite. Considering a single day in isolation, this isn't very severe, but when this nausea and loss of appetite lasts multiple weeks at a time, it can have a significant health impact. Additionally, a sense of spatial disorientation tends to coincide with the nausea. This disorientation is not of a spinning vertigo variety. Rather, it is a vague feeling that the environment isn't stable around my body. I don't seem to have problems with balance in the course of normal activities when my eyes are open, but my instinct is that I don't feel aware enough of my orientation relative to the ground to safely stand on a step ladder and stretch with both hands to manipulate a ceiling light fixture. When I have this spatial disorientation symptom, if I try to stand still with my eyes closed, my upper body tends to sway and I might take a step (Romberg's test). I can slightly, but not completely, limit the amount of sway if I very deliberately focus on how my leg muscles feel as my body starts to shift position. I don't sway or need to take a step when I don't have LED symptoms.
Is there photophobia (sensitivity to light) or phonophobia (sensitivity to sound)?
Common migraine without aura: Yes, there is photophobia. The normal brightness of any light source hurts both of my eyes a little and tends to significantly exacerbate my migraine headache. Every kind of light (sunlight, incandescent, fluorescent, flickering LEDs, and completely flicker-free LEDs) are a little painful in both eyes and strongly intensify the left side forehead headache when I have a migraine. I prefer to be in a room that is as dark as possible. Incandescent light on the dimmest possible setting still feels too bright. The intensification of the migraine headache happens while I see the light and the headache tends to immediately feel slightly better if I turn off the light. I do not experience light brightness photophobia when I do not have a migraine. I do not experience phonophobia.
LED symptoms: In some ways I have photophobia and in some ways I do not. When I have LED symptoms, I prefer to be in the sunlight - it not only doesn't hurt, but might make my head feel slightly better. Completely flicker-free LEDs also do not bother me at all. However, I am extremely sensitive to any flickering light. Flickering LEDs are very painful. They cause sharp pain behind my right eye while I am in the light and they exacerbate the dull headache pain and pressure surrounding my right eye and in my right temple and the effects are long-lasting. The headache tends to build in intensity fairly slowly. The headache might not start for about half an hour after the flicker exposure begins and the headache tends to intensify further for hours to days after the flicker exposure ends. The headache intensity correlates with my cumulative flicker exposure, but unlike the sharp pain behind my right eye that begins immediately in flickering light and ends immediately when the light goes off, the headache pain builds fairly slowly and tapers much more slowly. This type of photophobia occurs virtually any time I am exposed to ambient LED light flicker or screen flicker.
I have become more sensitive to flickering light since the 2018 symptom onset. Beginning with a 3-hour exposure to flickering LEDs in April 2021, I have become sensitive to the flicker of some incandescent lights when I already have LED symptoms (causing mild pain and/or nausea) and have become more sensitive to the flicker of fluorescent lights. Sunlight and completely flicker-free LEDs have never caused or exacerbated my LED symptoms. I do not experience phonophobia.
I usually experience these two types of photophobia (from common migraine or from LEDs) at different times, but also sometimes experience them concurrently if a common migraine starts while I am already experiencing LED symptoms. Successful medicating of a common migraine with ibuprofen also stops the light brightness photophobia in both eyes, but has no effect on my LED symptoms or flicker-associated photophobia pain in my right eye.
Other secondary neurological effects?
Common migraine with aura: None.
LED symptoms: I have concentration problems and severe short-term memory impairment for days to weeks after exposure to flickering LEDs, depending on the severity of exposure. For example, I've walked to the bathroom to brush my teeth in the morning and forgotten for a few minutes why I went there. I can't do simple Sudoku puzzles (on paper) because I can't even briefly keep the positions of any of the numbers in my short-term memory (these puzzles are easy for me when I don't have LED symptoms). The clarity of my writing deteriorates because I can't remember the previous sentence or hold all of the ideas for a single sentence in my head at once. I can't proofread for similar reasons. I can't add a series of single digit numbers in my head (which as a teacher since 2006, I did on a routine basis when grading papers, never having trouble with the task before 2018 and rarely making errors). I have trouble remembering new aural information and have trouble constructing articulate sentences when having conversations where the topic is new and of any complexity. My long-term memory is unaffected. I can recall and teach previously-designed lessons for fairly complex subjects - chemistry and molecular biology, including remembering previous strategies for guiding students to an understanding of these subjects. My concentration problems do not seem to be an issue taking in visual information, per se. Rather, I seem to have trouble holding new information in my short-term (working) memory.
I have significant alterations to my sleep patterns with hypersomnia in the first day or two following a serious flicker exposure and insomnia for weeks to months following that. For example, I'll tend to fall asleep very early (~6pm) in the first couple of days following a serious exposure. Then a few days later, I'll start to wake up in the middle of the night or early morning and be unable to fall back asleep for hours. This happens every night for weeks to months. I'm not feeling anxious and my mind isn't racing. I just can't fall back asleep. I'm not waking up due to pain - the pain is usually lessened when I wake up. The inability to get enough sleep at night, along with my inability to eat properly due to ongoing nausea, contributes to extra daytime fatigue. When I don't have LED symptoms, it's quite rare for me to have any trouble sleeping at night.
In addition to the symptoms already described, another common symptom is a slightly swollen right upper eyelid. It is slightly difficult to open completely - the eyelid seems very slightly puffy and the space into which it needs to fold feels too tight. When the eyelid feels most swollen, wearing gas-permeable contacts tends to irritate it and sticky mucus collects in the eye if wearing the contacts (I wore contacts one such day then stopped because of the irritation to the inner surface of the eyelid).
On about half a dozen occasions, I've experienced transient, but severe central vision blurriness in my right eye that lasts about a minute. It seems like there's a film partially obscuring my vision, but there isn't any mucus obscuring my vision - rubbing the eye doesn't change anything and the blurriness just goes away on its own within about a minute.
The neuro-ophthalmologist who had flickering LEDs in the new office detected peripheral blindness in my right eye in a visual field test. This was before he dilated my eyes. When I returned the next week to repeat the test, but protected my eyes from the clinic light, I did not have any blindness.
Out of the many months that I've experienced LED symptoms, there have been a few days that the symptoms have been most intense and that additional symptoms have occurred. These additional symptoms include my right temple becoming painful to the touch, the pain in the temple taking on a pounding quality, specific points on the right side of my scalp becoming painful to the touch, and an intensification of the feeling of tissue swelling around my right eye increasing to the point that it felt like there was pressure on the muscles controlling the movement of my right eye in its socket. In this case, these muscles hurt when reading a paper source and even when moving the eyes with my eyes closed. This is the only time I've experienced "eyestrain," and it only happened on about 2 days overall.
Since the significant flickering LED exposure in April 2021, I've experienced more common migraine episodes than usual. These have tended to occur around the time I've had a moderate re-exposure to flicker that's restarted some LED symptoms. I can't say for sure, but it's possible that LED symptoms might increase the likelihood of having common migraine symptoms too. Taking ibuprofen still stops the common migraine symptoms, but has no effect on the LED symptoms. I know common migraine symptoms are beginning on top of my LED symptoms when I feel a little pain in my left eye due to light in addition to the right eye pain, when any light source (including sunlight or flicker-free LED light) causes both left and right side eye pain, and when the headache begins to include the left side of my forehead.
I suspect that flicker causes neuroinflammation around my eye, leading to the eyelid puffiness and feeling of pressure around my eye. I suspect that it was only when this inflammation was most severe that moving my eye became painful. I suspect that flicker causes neuroinflammation in the trigeminal ganglion, leading to the pain and feeling of pressure in the temple. I suspect that sensitization in the thalamus leads to the allodynia and other symptoms that might involve the cortex or other parts of the brain.
Common migraine without aura: Although completely debilitating when in progress, these migraines have little impact on my quality of life and have not yet impacted my work. They only impacted my school attendance at age 13. These migraines are fairly infrequent and usually easily controlled with ibuprofen.
LED symptoms: Although the symptoms on a given day are not particularly debilitating, the duration of symptoms and their long-term effects in the aggregate have a significant impact on my quality of life and ability to do my job effectively (Timeline of 2021 "LED" Symptoms). No over-the-counter pain medication helps, so I don't take anything. At work, I cannot enter facilities that use flickering LED lights. I cannot use a computer for longer than a few minutes at a time, and even that is a risk. I cannot use some applications with inherent flicker, like Zoom. I cannot spend much time on websites because they too often include flicker. Because flickering LEDs have recently become increasingly ubiquitous in NYC, with businesses swapping out fluorescent lights for flickering LEDs, I no longer have a way to shop for groceries that doesn't involve exposure to LED flicker, either from the local stores, from a screen, or from building lights and lights on public transportation if I travel to a distant store.
Stimuli that do not trigger or intensify LED symptoms for me:
Completely flicker-free LED light bulbs (containing special circuitry that completely eliminates any 100/120 Hz mains flicker and that has completely constant light output). These are completely flicker-free LED bulbs that I own and use for hours each day; these have never caused "LED" symptoms for me and I cannot detect any flicker by slow-motion smartphone video:
LEDs powered by constant direct current. Even battery power does not necessarily ensure that the current to the LEDs is constant. For example an LED book light using battery power at full power seems to not cause symptoms and seems not to flicker by slow-motion cell phone video. However, when switched to a dim setting, it has 100% flicker (the LED receives intermittent direct current) and causes LED symptoms for me. A string of LED holiday lights with an AC/DC converter seems not to flicker and does not cause symptoms for me.
A very bright LED blue light transilluminator used for imaging DNA in agarose gels from 2011-2019, and similar blue-light transilluminators from 2019-the present. There are 3 different brands of this kind of device and all have AC/DC power adapters and do not have any flicker. They have never triggered or exacerbated my symptoms and I've even tried looking at them for a long period of time without effect.
Prior to the late spring of 2021, incandescent lights had not bothered me. Now many do, causing a little pain or nausea, and after long exposures, headaches. I think the incandescent Edison bulbs that I own haven't bothered me yet, but I can't say conclusively because I now rarely use them, having added lamps that will work with Waveform LED bulbs in every room where I had previously used incandescent bulbs. As I slowly recover from the April 2021 flicker exposure, I am gradually becoming more tolerant of incandescent lights again. In November 2021, during a full day spent at a home with incandescent lighting, I could tolerate the incandescent light for a few hours without pain, but after that time felt pain behind my right eye when in the light, developed a minor headache and become unusually tired by the early evening. In contrast, in June, these same incandescent lights were painful after a few minutes and caused or exacerbated headaches.
Stimuli that trigger LED symptoms for me:
LED lights with ≥120 Hz flicker
Flicker frequency of 120 Hz to at least ~1500 Hz (very rough estimate from video) has been a trigger. The flicker percent of LED lights that trigger symptoms has ranged from 100% down at least 0.7%. I have experienced LED symptoms from every LED light from which I can detect any flicker on a slow-motion smart phone video. I have also experienced LED symptoms from LED lights that manufacturers have confirmed have some flicker, but for which I can't definitively detect flicker using a slow-motion smart phone video. The following are LED lights that have caused symptoms for me for which I have statistics:
2013 Cree A19 dimmable LED, (model BA19-08027OMF-12DE26-1U100), 120 Hz flicker, probably between about 20% and 40% flicker based on similar models reviewed on LED benchmark. I had this bulb in a lamp behind my couch and tended to have this light on only when watching TV on a CCFL screen. Prior to the fall of 2018, I felt very vague disorientation in this light, but tried to ignore the feeling, thinking that I just must not like the difference in color temperature compared to incandescent bulbs. Once my LED symptoms started in the fall of 2018, this bulb was noticeably painful and exacerbated my LED symptoms. I replaced it with an incandescent bulb. in 2021, I replaced the incandescent with a completely flicker-free LED.
Apartment #1 common hallway LED fixtures installed in 2016. These have 100% flicker at 120 Hz. I'm exposed to these lights for less than a minute each time I enter or leave my building. Prior to 2018, I had a vague sense of not particularly liking the lights. Once my LED symptoms started in the fall of 2018, these lights became increasingly painful and seemed to exacerbate my symptoms. By the summer of 2019, these lights weren't painful anymore for the seconds I was in the hallway. They became quite painful again and exacerbated my LED symptoms beginning with my new severe round of LED symptoms beginning in April 2021. They are still painful now in November 2021.
Apartment #2 common hallway LED fixtures installed in 2021. These have 100% flicker at 120 Hz and usually have additional PWM dimming but switch to full brightness (also with 100% flicker) on a motion sensor. These hallways are particularly painful to traverse - much more painful and exacerbating of LED symptoms than the lights in apartment #1.
An LED projector with 120 Hz flicker illuminating a screen about 20 meters away that was the main light source in an auditorium during a conference in June 2021 while I was still experiencing sleep problems and rapid LED symptom restart in response to flicker following the serious exposure to 3 hours of LED flicker on April 1, 2021. I felt vague spatial disorientation immediately upon entering the auditorium and developed sharp pain behind my right eye after less than 5 minutes. At that point, I checked the auditorium lights with a slow-motion smartphone video and saw that the projected light on the screen alternated between bright and quite dark at 120 Hz. I put on a hat and shade 5 welding glasses that sat closely on my face, but had gaps in a foam liner and didn't make a complete seal. I tried keeping my eyes shut, just listening to the talks, but this was not sufficient to stop the sharp pain behind my eye. Headache pain and pressure started to develop. I then covering the inside of one of the lenses with foil from a food wrapper and with paper that I had on hand. This blocked, most of the light on one eye, but some light still leaked around the edges of the lens. I still felt the sharp pain and the headache pain and pressure worsened. As usual, the sharp pain behind my right eye would stop immediately when I left the auditorium and entered an area illuminated only by sunlight. I skipped half of the morning talks and half of the afternoon talks to sit in the sunlight and give my head a rest. This incident caused headache, head pressure, nausea, and disorientation lasting several days and exacerbated ongoing sleep problems. This incident indicates that I will develop symptoms from flicker even when I'm not focusing my eyes on anything.
"White" LED bulbs that have 120 Hz flicker where the flicker is between slightly red and slightly green light (see photos below from a Blick Art Materials store). Less than a minute in this light while wearing a hat and shade 5 welding glasses triggered a headache behind my right eye (mostly pain without much pressure) and nausea with loss of appetite that lasted at least 6 hours, until I fell asleep.
Various LED bulbs tested by me in 2021 in an attempt to find LED bulbs that would not cause symptoms for me - all of these caused symptoms for me that started in seconds to minutes and all have 120 Hz flicker that was easily detected on a slow-motion smart phone video:
Philips dimmable PAR 20 advertised on Amazon as “flicker-free” (model 9290013169); fine print on packaging indicates that they are only free of "visible" flicker.
Sunco dimmable PAR20 advertised on Amazon as “flicker-free” (model L9-PAR20DWP-7W); I called Sunco and a sales rep acknowledged that they are only free of "visible" flicker.
Philips dimmable A19 LED advertised on Amazon as “flicker-free” (model 9290019409B); fine print on packaging indicates that they are only free of "visible" flicker.
GE soft white 60W-equivalent dimmable A19 LED (product code 67615)
Target soft white 60W-equivalet non-dimmable A19 LED (model A800830).
After reporting Philips PAR20 9290013169 bulbs to the Consumer Product Safety Commission for their causing of my LED symptoms in 2021 (they had been recently added to someone else's apartment), Philips kindly sent us replacement bulbs to try, but they also caused symptoms for me - symptom onset was just slightly slower than for the original bulbs.
The replacement "eye comfort" bulbs that still cause symptoms (disorientation initially, interestingly without sharp pain behind the eye initially, followed by dull headache near eye and temple that lasted 72 hours after 30 min of exposure) are model 9290019867 and Philips shared that they have the following flicker stats: 13.813% flicker, flicker index = 0.040, Pst = 0.294, SVM = 0.453. I could also tell that they flicker at 120 Hz using a smart phone slow motion video. Instead of using these bulbs, we reconfigured all of the ceiling fixtures to have open cans that wouldn't overheat with incandescents and we re-installed incandescents - even though their flicker is slightly irritating, it's vastly better than the flicker of LEDs. We would prefer completely flicker-free LEDs both for health and energy efficiency reasons, but cannot find a current manufacturer of this PAR20 style bulb, although Philips used to make them in 2013 - see LEDbenchmark.
This is what I know about the flicker stats of industrial-style LED strip lights that have caused my longest-lasting LED (and see the following graph and document with spreadsheet):
LED strip lights: ~1000 Hz flicker based on my slow-motion smart phone videos and manufacturer data. Flicker percent from 0.7% at full brightness (typical usage) to 30% when dimmed (tried once) based on manufacturer data.
LED strip lights: ~800 Hz based on my slow-motion smart phone video. Flicker percent from 0.7% to 8.13% at full brightness based on lighting consultant measurements.
LED strip lights: ~1500 Hz flicker with a probable square waveform based on sharp delineation between dim areas and brighter lines in my slow-motion smart phone video. Flicker percent might have been roughly around 20% based on video. Caused immediate pain when entering a room with these lights dimmed and caused other longer-lasting symptoms.
LED strip lights: Waveform 4000K Centric Daylight strip lights being controlled by a Waveform CENTRIC SERIES™ Flicker-Free Non-Dimmable Power Supply for LED Strip. These seem to have 1.27% flicker at 120Hz (see measurements below). Since I've been regularly using flicker-free light bulbs from this same company since May 2021 without symptoms (Waveform Flicker-Free A19 bulbs), it was immensely disappointing to learn that this power supply advertised as "flicker-free" causes symptoms for me and is not actually flicker-free. In the presence of the strip light controlled by the Waveform Centric Series Non-Dimmable Power Supply, I immediately felt a vague disorientation, but I didn't have the sharp pain behind my eye that I often get when in the presence of flickering LED light. On the first day of testing on 3/23/22, I was already feeling strong headache pain and pressure from exposure to more severely-flickering LEDs in testing of other lights just before (see "Lessons from mistakes in flicker testing" section below). After about 45 minutes in this room with only light from the strip attached to the Centric Series Non-Dimmable Power Supply, the pressure in my head began to go down and I stayed in this light for about another 45 minutes without noticing the existing headache worsening. So even though the light made me feel slightly disoriented, I decided to try it again the next day. On the second day of testing for 1.5 hours, facing away from the bright strip, I immediately felt vaguely disoriented in the light, had occasional twinges of sharp pain behind my right eye, and occasionally felt more noticeably disoriented - at one point I had to grab the chair to maintain my balance when standing up. I also felt too nauseous to finish the second half of a sandwich for lunch. However, since all of those symptoms didn't seem definitively conclusive, I came back the next day. On the third day, I stayed in this room, facing away from the strip, for 5 hours and 50 minutes (11am-4:50pm). The light again immediately made me feel vaguely disoriented. I occasionally felt a slight twinge of pain behind my right eye. After 3 hours, I was feeling very tired and was not able to concentrate on the planning work I was doing in a paper notebook. I walked around the room to try to become more alert. I decided to try to do a Sudoku puzzle (in a paper book), both as a break from work and because I use these puzzles to gauge whether my short-term memory is compromised. I worked on a new puzzle (so this meant inserting easy starting numbers) for about 3 minutes, during which time I felt it was a little hard to focus. My speed felt reasonable, but I made a careless mistake of repeating a number and not noticing the error immediately (unusual when I’m more normal). After those few minutes I started to notice a pain in my right temple, so I put the book away and didn’t look at anything else requiring reading or thinking - just in case one of those activities had been a trigger. Over the next hour and 20 minutes, the pain in my temple intensified and I also started to feel noticeably nauseous and have increasingly intense spatial disorientation. Interestingly, I didn’t have any pressure in my temple, which is one of my common symptoms from screen use or from very intense flicker exposure. I tried shutting off the lights for a few seconds and closing my eyes. My balance with my eyes closed was slightly abnormal the first time I checked just after 3:30, but became noticeably compromised after another hour. Having difficulty maintaining my balance with my eyes closed is usual for me if I am spatially disoriented. By the time I left, the head pain was moderately intense and the spatial disorientation and nausea were moderately severe. I’ve experienced worse of both in the past, but this was fairly bad. I felt slightly better immediately upon getting into the sunlight at 4:50. That evening, my headache lasted until ~7pm and I was unusually tired in the evening and fell asleep hours early. Nausea, spatial disorientation, and lack of appetite continued the next day (Saturday) and until mid-afternoon on Sunday. Although these lights seemed to be fairly clearly symptom-inducing by this point, I decided to try them one more time to confirm that the effects were reproducible. On Monday, the 4th day of testing, I stayed in the room for 3 hours (9:45-12:45), facing away from the strip. The lights felt uncomfortable (vaguely disorienting) right away and I started feeling definitely motion-sick within 20-30 minutes. By 11:30 I had a headache. I hadn’t been reading -just talking on the phone and also starting to sort materials and mapping how to cut them - basically an arts and crafts project to create a new kit for teaching. By about 11:45, I was having trouble concentrating enough to even keep working on this - a task not requiring hardly any thinking. I turned off the lights briefly and had a very hard time maintaining my balance - I swayed backwards into the wall. To test myself further, I tried Sudoku again and only managed to place 2 numbers in about a half hour - super slow. Usually an entire puzzle in this book takes me about 20 minutes. I just couldn’t concentrate. I noticed that my headache worsened when working on the Sudoky puzzle. The headache would lessen slightly if I stopped looking at the puzzle. Upon leaving, I had a headache, nausea, spatial disorientation, and a lack of appetite that lasted 2 more days, through Wednesday. Tuesday evening I felt like a left-side migraine might be starting (slight pain in left forehead and pain behind both eyes from light brightness) so took ibuprofen and those migraine symptoms stopped, but the previously-existing flicker-induced symptoms did not stop. I had increased sensitivity to flicker and had other symptoms from minor flicker triggers the rest of the week. Saturday morning, I woke up early with a partially developed migraine headache centered in my right temple - the first time for this location for a migraine in over 30 years of occasionally having migraines on the left side (This 4/2/22 migraine was a throbbing headache worsened by movement or light brightness with intense nausea - the overall intensity wasn't yet at full force for a migraine and I took ibuprofen which lessened the headache pain, stopped the other migraine symptoms, and probably prevented symptoms increasing to the point of vomiting). Although it was in a new location - at the site of my flicker symptoms - this migraine fits a pattern I've noticed recently of migraines happening within ~5 days of a significant flicker exposure. Residual headache and fatigue following the migraine lasted into Sunday morning.
Conclusion: This lighting setup causes symptoms that are too severe to be compatible with working in the light. The loss of short-term memory and severely compromised ability to concentrate make me unable to do my job.
Data for Waveform 4000K Centric Daylight strip lights being controlled by a Waveform CENTRIC SERIES "Flicker-Free" Nondimmable power supply
Flicker frequency: 120 Hz
% flicker (for magenta region highlighted in graph): 1.27%
% flicker (overall, determined by meter software): 2.325%; Note: I was told verbally that in a repetition of this test, the lighting consultant obtained a reading of 1.3% flicker with the meter software.
Calculation of % flicker:
Distance from min to max point measured in Photoshop: 689.60 px
Height of indicated portion of wave (magenta line) measured in Photoshop: 375 px
If the minimum of the magenta line was set at 0.2260, the maximum of the magenta line would be at 0.2318. [(0.2367-0.2260) *(375 px/689.60 px)+0.2260 = 0.2318]
% flicker = 100% * (max-min)/(max+min) = 100% * (0.2318-0.2260)/(0.2318+0.2260) = 1.27%
It is unclear to me what creates the broad peaks and valleys in the graph of luminosity vs. time. I asked this question of the lighting consultant over the phone the day the testing was being done. They didn't have a definitive answer, other than to say that the readings were made with a handheld meter that wasn't necessarily kept completely steady. Theoretically, the amount of light observed by the meter would depend on the exact distance of the meter's sensor from the light source. I was told verbally that after our conversation, they repeated the test, obtaining a meter reading of 1.3% for the flicker of these lights, but I was also told that the same broad fluctuations happened even when the meter was held steady against the wall (I'm still confused as to how both statements can be true). I wonder to what extent there really is sub-120Hz variation in light intensity and I wonder to what extent it might contribute to my symptoms.
This strip light was installed on a wall and was the only light source in the room during testing with the meter and during testing on me. The flicker was not visible on a smart phone slow motion video.