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Why does strobe lighting trigger seizures in photosensitive epilepsy?

Why does strobe lighting trigger seizures in photosensitive epilepsy?



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Photosensitive epilepsy (PSE) is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights, bold, regular patterns, or regular moving patterns.

Why does strobe lighting trigger seizures in photosensitive epilepsy?


Seizures induced by stroboscopic lights are an example of reflex seizures. This type of epilepsy includes seizures evoked by touch and movements as well. The mechanism behind generalized reflex seizures (generalized epilepsy, as opposed to partial epilepsies, is accompanied by a loss of consciousness) was abstracted nicely by Ferlazzo et al., 2005:

Patients with [] generalized reflex seizures appear to have regions of cortical hyperexcitability overlapping or coinciding with areas physiologically activated during specific sensory stimulations and cognitive or motor activities. When these areas receive appropriate afferent volleys and a critical mass of cortex is activated, an epileptic activity is produced that ultimately involves cortico-reticular or cortico-cortical pathways resulting in a generalized or bilateral epileptic event.

In other words, stimuli such as stroboscopic light evoke activity in sensory cortex. If the area of excitation is large enough and occurs in a region of the brain that has an epileptic focus (hyperexcitable cortex) than it may trigger a seizure characterized by an uncontrolled wave of activity spreading across the cortex.

Specifically for flashing-light induced seizures it is thought that seizures start in the visual cortex in the occipital lobe due to impaired cortical mechanisms of contrast gain control for certain visual patterns, producing an abnormal excitatory response to patterns of relatively low temporal frequency and high luminance contrast. Specifically, the seizures may be caused by a loss of control over high-frequency oscillatory processes that normally operate transiently to connect the involved neural assemblies. Generalized seizures can occur if normal excitation of visual cortex involves a 'critical mass' of synchronized activity in a cortical area with synchronization and subsequent spreading of excitation from the occipital lobe trigger zone (Parra et al., 2005).

References
- Ferlazzo et al., Brain (2005); 128: 700-10
- Parra et al., Curr Opin Neurol (2005); 18(2):155-9


Neuron overload: why flashing light causes epileptic seizures

Earlier on Friday, a suspect was arrested in Salisbury, Maryland, for sending a virtual attack through Twitter to Newsweek senior writer Kurt Eichenwald last December. The suspect, whose name was confirmed by a law enforcement official as John Rivello, sent a GIF of a strobing image to Eichenwald on the social media website that was deliberately intended to trigger a seizure.

The message, sent by an account with the Twitter handle @jew_goldstein, followed Eichenwald's appearance on Tucker Carlson Tonight. Eichenwald has epilepsy, a diagnosis he has spoken about publicly. "You deserve a seizure," the Twitter post containing the image read. The strobe did lead to a seizure, and Eichenwald had vowed to take legal action.

Despite the apparent ease with which light can trigger a seizure, much about the phenomenon is poorly understood by the average Twitter troll and other nonexperts. The key is electricity, the invisible force that allows our brains to function.

Millions of neurons constantly transmit electrical signals that influence our every move, thought and feeling. The condition called epilepsy renders some people, usually through a genetic predisposition, susceptible to sudden and abnormal discharges of electricity resulting from sensory overload or chemical changes in the body. These changes cause collections of neurons to release a relatively large quantity of electricity all at once, commonly known as a seizure. These bursts are often unpredictable and cannot be controlled while they are happening. An estimated 150,000 people in the U.S. develop this condition each year, making it the fourth most common neurological problem in the country.

In people with photosensitive epilepsy&mdashabout 5 percent of all epilepsy cases&mdashlight is the seizure-triggering culprit. Specifically, lower wavelengths of light&mdashthe flash of a strobe, sunlight flashing intermittently through a picket fence&mdashmay trigger seizures. These patterns, says Joseph Sirven, a neurologist with the Mayo Clinic in Arizona, disrupt brain function.

The key is the speed of the flashing. Most photosensitive epileptic seizures are sparked by five to 30 flashes per second. Pulses of light coming at the brain faster do not pose the same danger. The slower the pace, says Sirven, "the more closely it approximates brain function." Although the exact pathway is not clearly understood, this additional electricity entering the brain is converted to a signal that leads to clusters of neurons releasing their electricity all at once.

Sirven explains that the propensity for flashing light to trigger seizures&mdashrather than, say, a strong smell or something touching the skin&mdashmay be because the area of the brain that controls vision is confined to the occipital lobe, a discrete area of the brain. The neurons processing information from our other senses, by contrast, are more widely distributed.

A photosensitive seizure does not lead to permanent damage, but a person may experience temporary memory or language loss after one. And a seizure happening while, say, driving could prove very dangerous. People with epilepsy also fear having a seizure in public, an event that could be detrimental socially or professionally. Children may be teased. Interacting with the public as part of a job may worry an employer. "There are consequences," says Sirven. "This is a very stigmatizing condition, and there is no way around it."

Internet imagery is not a specific risk category, but Sirven says he has heard about parents or patients mentioning time spent playing video games or reading material online when they discuss seizures. "It's not uncommon to hear that as an inciting factor," he says. And while the number of people living with photosensitive epilepsy has not changed in recent years, the number of seizures has increased.

"It's hard to know whether people have become more sensitive," Sirven says, "or whether there are more risk factors."


Can a bright light or strobe light cause a seizure?

F or about 3 percent of people with epilepsy, exposure to flashing lights at certain intensities or certain visual patterns can trigger seizures, according to the Epilepsy Foundation. Due to a condition called photosensitive epilepsy, lights can trigger seizures in one in 10,000 adults and one in 4,000 children and adolescents. Many people are unaware of a sensitivity to flickering lights or certain patterns until they have a seizure.

Discuss with Your Doctor

Most people who've been diagnosed with epilepsy undergo an electroencephalogram (EEG), which has its own flashing light. As part of a routine EEG, a strobe light flashes at different frequencies while a technician monitors the recording. Technicians usually alert patients about the potential for a reaction and monitor for it. If they see an electrical buildup on the monitor they know to turn off the lights.

Other Light Triggers

A flashing light is just one potential trigger. Other triggers include flickering or rolling images on a TV screen or computer monitor, video games or TV broadcasts containing rapid flashes or alternating patterns of different colors, and intense strobe lights like visual fire alarms. Natural light, such as sunlight, especially when shimmering off water or flickering through trees or through the slats of window blinds, can also trigger seizures in some people. Stripes of contrasting colors and flashing lights on tops of buses or emergency vehicles are other triggers.

Strategies for Avoiding Triggers While.

Watching TV: Watch in a well-lit room to reduce the contrast between light from the set and light in the room and sit as far back from the screen as possible. Avoid watching the monitor for long periods of time. If necessary, wear polarized sunglasses to reduce glare.

Playing video games: Sit at least two feet from the screen in a well-lit room and reduce the brightness of the screen. Do not play when tired. Take frequent breaks from the games and look away from the screen every once in a while. Do not close and open eyes while looking at the screen blinking can trigger a seizure. Cover one eye while playing, alternating which eye is covered, and remember to turn off the game if strange or unusual feelings or body jerks develop.

Using a computer: Use a flicker-free monitor (LCD display or flat screen) and a glare guard. Consider wearing nonglare glasses, and take frequent breaks.

By signing up, you agree to our Privacy Policy and Terms.

Recently, efforts have been made to reduce the risk of a seizure for people with photo-sensitive epilepsy. For example, warnings about the potential for seizures have been added to many video games, and flashing emergency lights can flash only once every two seconds, a frequency below the number needed to trigger a seizure.

Dr. Fisher is the Maslah Saul MD Professor of Neurology at the Stanford University School of Medicine in Palo Alto, CA, and director of the Stanford Epilepsy Center.


How Strobe Lights Cause Seizures

To revist this article, visit My Profile, then View saved stories.

To revist this article, visit My Profile, then View saved stories.


After taking a look at M.I.A.'s new website, I started wondering exactly how strobe lights cause seizures. (Take a look. You'll see what I mean. Wait -- maybe, *don't* take a look, unless you're sure it's safe for you.)

The condition, called photosensitive epilepsy, affects about one in twenty people with epilepsy. Seizures are triggered by light flashing between 5 and 30 times per second geometric patterns, with heavy contrasts between light and dark, are common culprits, especialy if flashing or changing direction.

Recognized in antiquity but brought to modern infamy in 1997 when an episode of Pokemon produced a wave of seizures in Japanese children, this visually-induced form of epilepsy isn't well-understood. Observing the brains of people undergoing such seizures is practically and ethically impossible, so most research has been done in primates.

The condition appears to involve the primary visual cortex, which processes visual information. The cortexes of photosensitive are easily excited flashing patterns overwhelm them, setting off a barrage of neuron firing that overwhelm the cortex and spread to other parts of the brain.


Strobe Light Induced Epilepsy

Professionals in the entertainment lighting industry are often questioned about the use of strobe lights in public, mostly due to the public’s perceptions that strobes will cause epilepsy. Below are some technical references that may help educate you and your clients.

Epilepsy Foundation

http://www.epilepsyfoundation.org/about/photosensitivity/
The frequency or speed of flashing light that is most likely to cause seizures varies from person to person. Generally, flashing lights most likely to trigger seizures are between the frequency of 5 to 30 flashes per second (Hertz). […] The likelihood of such conditions combining to trigger a seizure is small.
To reduce the likelihood of the strobe light triggering a seizure, the Epilepsy Foundation’s professional advisory board recommends that
* the flash rate be kept to under 2 Hertz with breaks every so often between flashes

Epilepsy Action (UK)

What Causes Light-Induced Seizures? (from Epilepsy.com)

Photosensitivity is an intricate medical problem. Scientists have been able to identify many of the triggers, but the mechanism that makes the brain hyper-excitable when the retina gets stimulated in a certain way remains poorly understood. The key features of a provocative stimulus, however, are outlined in a consensus reached by a group of international experts gathered by the Epilepsy Foundation. These are:

    The flicker of the light source, and the “frequency” at which the light changes. In other words, how many times the light flashes in a second. Generally, flashing lights between the frequencies of five to 30 flashes per second (Hertz) are most likely to trigger seizures. In order to be safe, the consensus recommends that photosensitive individuals should not be exposed to flashes greater than three per second.

There are other factors involved, as well. One is the viewer’s distance from the light source because it directly affects the field of vision. For instance, going back to the example of television viewing, the closer the person gets to the screen, the greater the risk. More of the visual field is occupied therefore, more of the brain gets stimulated.

The second factor is color . Certain colors are critical in particular, the so-called saturated “deep” red. Within the visual spectrum, this color is the one with the longest wavelength and it can be easily eliminated by wearing appropriate optical filters (blue lenses). However, filtering may also drastically affect visual perception. For instance, it is important that drivers, if wearing special filtering glasses to gain protection against possible seizures, do not loose the ability to recognize the color of signals at intersections. On the other hand, these devices may be helpful for passengers riding in cars and during other everyday activities not requiring sharp color discrimination. Pairs of quickly-changing colors, particularly red and blue, are also known to be more provocative than others.


Why Do Some Still Images Trigger Seizures?

By now, most people are aware of strobe lights’ ability to induce photosensitive epileptic seizures. A troll allegedly gave a journalist a seizure with a tweet . An episode of Pokémon sent almost 700 Japanese children to the hospital. But still images can cause seizures, too, and scientists are just now starting to figure out how that happens.

There’s still a ton we don’t know about seizure triggers, since there isn’t a reliable way to test them in humans or animals. A team of researchers from the University Medical Center Utrecht wanted to know what was going on in the brain that might help them better understand why some still images trigger seizures and others don’t.

“One particular type of brain wave. called a gamma oscillation, is particularly strongly driven by certain kinds of visual patterns,” Dora Hermes, lead author of a correspondence published today in Current Biology, told Gizmodo. A black and white bar pattern can induce these gamma oscillations in the brain’s visual cortex, the image processing part of the brain—and in an epileptic brain, the researchers hypothesize that the oscillations are linked with seizures.

Gamma oscillations are a much-discussed brain wave pattern, characterized by neurons firing rhythmically around 50 times per second. The researchers sifted through lots of old research, and found associations between images that caused seizures and those that produced narrow-band gamma oscillations in healthy individuals. Basically, if the image caused the visual cortex’s neurons to clap in unison at the gamma oscillation frequency, it was more likely to cause seizures in epileptic individuals. Those images that caused the brain’s neurons to clap out of sync were less likely to cause seizures.

“We hypothesize that the circuitry that produces these oscillations might also provoke a seizure in patients with photosensitive epilepsy,” said Hermes.

One neurologist, Khalid Hamandi from Cardiff University, pointed out to me that Hermes and her co-authors’ correspondence isn’t presenting new data, although it has nicely summarized information already out there. The link between gamma oscillations and epileptic seizures was observed in a 2003 study (but not with still images) for example.

But another professor, György Buzsáki from New York University, told Gizmodo in an email that he found the paper’s timing important. “Just a year ago, I would not even blink about this paper. However, this year is different.” You may have listened to a recent Radiolab episode about a new study demonstrating that flickering light at these gamma frequencies at mice suffering from Alzheimer’s reduces the level of a kind of plaque found in their diseased brains. This suggests that a future Alzheimer’s treatment might involve inducing these firing patterns in patients, potentially causing seizures.

“I expect that a large number of companies will try to sell their gadgets in the coming years, and many people will attempt flickering light in the hope of decelerating the progression of degenerative diseases,” Buzsáki wrote. “Without understanding first the mechanisms, this may be a dangerous venture. This report points to at least one danger, especially given that a large fraction of Alzheimer’s Disease patients are prone to epileptic activity.”

This paper only mentions black and white bars, but now the researchers want to test whether other still images might induce these gamma oscillations, too—the researchers don’t know, yet. For now, there’s a lot of experimenting ahead of them. “I’d like to emphasize that this is a review of the literature,” said Hermes. “We’re working on testing this by measuring it in various patient populations. This paper is really a hypothesis.”


What Triggers Photosensitive Seizures in Children?

Seizures in children with photosensitivity are triggered by lights that repeatedly flash in particular patterns and intensities. Because of this, triggers can range from the flickering of a television screen, computer monitor or fence shadows viewed from a moving vehicle.

Some sources, such as strobe lights or emergency lights, may seem obvious as potential triggers. But visual patterns and effects, especially stripes of contrasting colors, in any video medium, can also trigger a seizure.


Strobe Light Induced Epilepsy

Professionals in the entertainment lighting industry are often questioned about the use of strobe lights in public, mostly due to the public’s perceptions that strobes will cause epilepsy. Below are some technical references that may help educate you and your clients.

Epilepsy Foundation

http://www.epilepsyfoundation.org/about/photosensitivity/
The frequency or speed of flashing light that is most likely to cause seizures varies from person to person. Generally, flashing lights most likely to trigger seizures are between the frequency of 5 to 30 flashes per second (Hertz). […] The likelihood of such conditions combining to trigger a seizure is small.
To reduce the likelihood of the strobe light triggering a seizure, the Epilepsy Foundation’s professional advisory board recommends that
* the flash rate be kept to under 2 Hertz with breaks every so often between flashes

Epilepsy Action (UK)

What Causes Light-Induced Seizures? (from Epilepsy.com)

Photosensitivity is an intricate medical problem. Scientists have been able to identify many of the triggers, but the mechanism that makes the brain hyper-excitable when the retina gets stimulated in a certain way remains poorly understood. The key features of a provocative stimulus, however, are outlined in a consensus reached by a group of international experts gathered by the Epilepsy Foundation. These are:

    The flicker of the light source, and the “frequency” at which the light changes. In other words, how many times the light flashes in a second. Generally, flashing lights between the frequencies of five to 30 flashes per second (Hertz) are most likely to trigger seizures. In order to be safe, the consensus recommends that photosensitive individuals should not be exposed to flashes greater than three per second.

There are other factors involved, as well. One is the viewer’s distance from the light source because it directly affects the field of vision. For instance, going back to the example of television viewing, the closer the person gets to the screen, the greater the risk. More of the visual field is occupied therefore, more of the brain gets stimulated.

The second factor is color . Certain colors are critical in particular, the so-called saturated “deep” red. Within the visual spectrum, this color is the one with the longest wavelength and it can be easily eliminated by wearing appropriate optical filters (blue lenses). However, filtering may also drastically affect visual perception. For instance, it is important that drivers, if wearing special filtering glasses to gain protection against possible seizures, do not loose the ability to recognize the color of signals at intersections. On the other hand, these devices may be helpful for passengers riding in cars and during other everyday activities not requiring sharp color discrimination. Pairs of quickly-changing colors, particularly red and blue, are also known to be more provocative than others.


How Strobe Lights Cause Seizures

To revist this article, visit My Profile, then View saved stories.

To revist this article, visit My Profile, then View saved stories.


After taking a look at M.I.A.'s new website, I started wondering exactly how strobe lights cause seizures. (Take a look. You'll see what I mean. Wait -- maybe, *don't* take a look, unless you're sure it's safe for you.)

The condition, called photosensitive epilepsy, affects about one in twenty people with epilepsy. Seizures are triggered by light flashing between 5 and 30 times per second geometric patterns, with heavy contrasts between light and dark, are common culprits, especialy if flashing or changing direction.

Recognized in antiquity but brought to modern infamy in 1997 when an episode of Pokemon produced a wave of seizures in Japanese children, this visually-induced form of epilepsy isn't well-understood. Observing the brains of people undergoing such seizures is practically and ethically impossible, so most research has been done in primates.

The condition appears to involve the primary visual cortex, which processes visual information. The cortexes of photosensitive are easily excited flashing patterns overwhelm them, setting off a barrage of neuron firing that overwhelm the cortex and spread to other parts of the brain.


Neuron overload: why flashing light causes epileptic seizures

Earlier on Friday, a suspect was arrested in Salisbury, Maryland, for sending a virtual attack through Twitter to Newsweek senior writer Kurt Eichenwald last December. The suspect, whose name was confirmed by a law enforcement official as John Rivello, sent a GIF of a strobing image to Eichenwald on the social media website that was deliberately intended to trigger a seizure.

The message, sent by an account with the Twitter handle @jew_goldstein, followed Eichenwald's appearance on Tucker Carlson Tonight. Eichenwald has epilepsy, a diagnosis he has spoken about publicly. "You deserve a seizure," the Twitter post containing the image read. The strobe did lead to a seizure, and Eichenwald had vowed to take legal action.

Despite the apparent ease with which light can trigger a seizure, much about the phenomenon is poorly understood by the average Twitter troll and other nonexperts. The key is electricity, the invisible force that allows our brains to function.

Millions of neurons constantly transmit electrical signals that influence our every move, thought and feeling. The condition called epilepsy renders some people, usually through a genetic predisposition, susceptible to sudden and abnormal discharges of electricity resulting from sensory overload or chemical changes in the body. These changes cause collections of neurons to release a relatively large quantity of electricity all at once, commonly known as a seizure. These bursts are often unpredictable and cannot be controlled while they are happening. An estimated 150,000 people in the U.S. develop this condition each year, making it the fourth most common neurological problem in the country.

In people with photosensitive epilepsy&mdashabout 5 percent of all epilepsy cases&mdashlight is the seizure-triggering culprit. Specifically, lower wavelengths of light&mdashthe flash of a strobe, sunlight flashing intermittently through a picket fence&mdashmay trigger seizures. These patterns, says Joseph Sirven, a neurologist with the Mayo Clinic in Arizona, disrupt brain function.

The key is the speed of the flashing. Most photosensitive epileptic seizures are sparked by five to 30 flashes per second. Pulses of light coming at the brain faster do not pose the same danger. The slower the pace, says Sirven, "the more closely it approximates brain function." Although the exact pathway is not clearly understood, this additional electricity entering the brain is converted to a signal that leads to clusters of neurons releasing their electricity all at once.

Sirven explains that the propensity for flashing light to trigger seizures&mdashrather than, say, a strong smell or something touching the skin&mdashmay be because the area of the brain that controls vision is confined to the occipital lobe, a discrete area of the brain. The neurons processing information from our other senses, by contrast, are more widely distributed.

A photosensitive seizure does not lead to permanent damage, but a person may experience temporary memory or language loss after one. And a seizure happening while, say, driving could prove very dangerous. People with epilepsy also fear having a seizure in public, an event that could be detrimental socially or professionally. Children may be teased. Interacting with the public as part of a job may worry an employer. "There are consequences," says Sirven. "This is a very stigmatizing condition, and there is no way around it."

Internet imagery is not a specific risk category, but Sirven says he has heard about parents or patients mentioning time spent playing video games or reading material online when they discuss seizures. "It's not uncommon to hear that as an inciting factor," he says. And while the number of people living with photosensitive epilepsy has not changed in recent years, the number of seizures has increased.

"It's hard to know whether people have become more sensitive," Sirven says, "or whether there are more risk factors."


Can a bright light or strobe light cause a seizure?

F or about 3 percent of people with epilepsy, exposure to flashing lights at certain intensities or certain visual patterns can trigger seizures, according to the Epilepsy Foundation. Due to a condition called photosensitive epilepsy, lights can trigger seizures in one in 10,000 adults and one in 4,000 children and adolescents. Many people are unaware of a sensitivity to flickering lights or certain patterns until they have a seizure.

Discuss with Your Doctor

Most people who've been diagnosed with epilepsy undergo an electroencephalogram (EEG), which has its own flashing light. As part of a routine EEG, a strobe light flashes at different frequencies while a technician monitors the recording. Technicians usually alert patients about the potential for a reaction and monitor for it. If they see an electrical buildup on the monitor they know to turn off the lights.

Other Light Triggers

A flashing light is just one potential trigger. Other triggers include flickering or rolling images on a TV screen or computer monitor, video games or TV broadcasts containing rapid flashes or alternating patterns of different colors, and intense strobe lights like visual fire alarms. Natural light, such as sunlight, especially when shimmering off water or flickering through trees or through the slats of window blinds, can also trigger seizures in some people. Stripes of contrasting colors and flashing lights on tops of buses or emergency vehicles are other triggers.

Strategies for Avoiding Triggers While.

Watching TV: Watch in a well-lit room to reduce the contrast between light from the set and light in the room and sit as far back from the screen as possible. Avoid watching the monitor for long periods of time. If necessary, wear polarized sunglasses to reduce glare.

Playing video games: Sit at least two feet from the screen in a well-lit room and reduce the brightness of the screen. Do not play when tired. Take frequent breaks from the games and look away from the screen every once in a while. Do not close and open eyes while looking at the screen blinking can trigger a seizure. Cover one eye while playing, alternating which eye is covered, and remember to turn off the game if strange or unusual feelings or body jerks develop.

Using a computer: Use a flicker-free monitor (LCD display or flat screen) and a glare guard. Consider wearing nonglare glasses, and take frequent breaks.

By signing up, you agree to our Privacy Policy and Terms.

Recently, efforts have been made to reduce the risk of a seizure for people with photo-sensitive epilepsy. For example, warnings about the potential for seizures have been added to many video games, and flashing emergency lights can flash only once every two seconds, a frequency below the number needed to trigger a seizure.

Dr. Fisher is the Maslah Saul MD Professor of Neurology at the Stanford University School of Medicine in Palo Alto, CA, and director of the Stanford Epilepsy Center.


Epilepsy and Light Sensitivity

The connection between epilepsy and light sensitivity is well established. There’s even a term for it – photosensitive epilepsy. It occurs when flashing lights, or alternating patterns of darkness and lightness, trigger a seizure. Even though it’s not that common, it can be devastating. The professionals with Make Great Light would like to share some information on why photosensitive epilepsy occurs, and what you can do about it if you have to deal with the condition on a regular basis.

Photosensitive Epilepsy in Brief

About one percent of the population has epilepsy, and about 3 percent of people with epilepsy have photosensitive epilepsy. It’s more common in younger people, and less common in people older than 20 years of age.

Flashing lights or patterns can trigger a seizure. Lights that flash anywhere between 3-30 times per second will typically lead to a seizure, but some people are so sensitive that they’ll be affected by a light that flickers less than three times per second. The types of patterns that can lead to a seizure can vary as well. Looking at alternating light and dark bars or strips can cause problems, as can viewing patterns that seem to move or flash.

Triggers of Photosensitive Epilepsy

These are just a few examples of some of the more common triggers of a seizure associated with photosensitive epilepsy.

  • Wearing virtual reality goggles can increase your risk. Images typically flash very quickly – so quickly, in fact, that the flashing alone may not trigger a seizure. The problem is that the field of vision is extremely large. When a larger portion of the brain experiences flashing, that can make a seizure more likely.
  • Faulty television or device screens that produce flickering.
  • Looking at an older type of television with a cathode ray tube.
  • Seeing sunlight through your window blinds, through trees, or seeing the reflection of sunlight off of the water.
  • Watching the repeating patterns of an escalator.
  • Being in a nightclub or at a concert and being exposed to strobe lights.
  • Fluorescent lights that flicker.
  • Cameras with more than one flash, or seeing several cameras flash at once.
  • Flashing bicycle lights.

Treatment and Management

Thankfully, photosensitive epilepsy can usually be treated very successfully. Treatment will typically involve taking AEDs, or anti-epileptic drugs, that are typically used for general seizures. There are also ways you can reduce the risk of suffering a seizure. Here are just a few.

  • Avoid playing video games for an extended period of time without taking a break. That can reduce the excitement and/or stress that can sometimes lead to a seizure.
  • Stay far enough away from your computer screen so that it doesn’t take up your entire field of vision.
  • If you suddenly see a trigger, such as a geometric pattern you didn’t expect, cover one of your eyes with one hand. That should help reduce the risk of a seizure.

Make Great Light Could Help

Make Great Light may be able to help if you have epilepsy and light sensitivity. Our NaturaLux™ fluorescent light covers emulate natural light, and eliminate the flickering that can lead to a seizure. If you work in an office under fluorescent light all day, get in touch with us to learn more. You can contact us online or give us a call at 612-399-6484.


Why and how can flashing lights trigger epilepsy seisures? What happens in the brain?

EDIT: I’m aware that there are many different kinds of epilepsy and many different kinds of seizures and many of these are not triggered by photosensitivity. I’m mainly wondering about the relevant types, but as I’m curious about seizures in general, feel free to post any information about how and why different forms are triggered (i.e what happens in the brain and why).

When nerve cells want to convey information they send action potentials (APs) to communicate to other cells. In the simple model the AP will reach the end (terminal bouton, yes I did spell that correctly) where there is a gap (synapse) to another neuron. A chemical (neurotransmitter) will be released that will cause the neuron on the other side to also fire an AP.

Of course the reality is a bit messier than that. Whilst this picture is definitely true not all neurotransmitters are excitatory. Most of them are excitatory, but some of them are inhibitory.

Imagine a neuron firing and causing another neuron downstream to fire. These neurons are now synchronised. And if this carried on then eventually all of your neurons would be synchronised. So it is important that neurons can not only turn other neurons on but also to turn them off - the switch needs to go in both directions. Otherwise you could end up was a cascade failure where a few neurons firing ended up exciting all the other neurons and then your whole brain would be synchronised and youɽ have no control.

Flashing lights - in those sensitive to photoepilepsy - cause a specific synchronised firing in the nerve pathways leading from the eyes into the Lateral Geniculate Nuclei (an important relay centre) and the Occipital lobe. We don't know exactly what happens as a pathway from here, but the belief is that this heavy synchronised firing spreads to the rest of the brain which is sensitive to excitatory inputs and have no areas firing more strongly to compete.

Note: it is not about the overall amount of "electricity" - inhibitory neurons carry just as much "electricity" as excitatory ones. It is about the synchronisation of the firing. I put "electricity" in "" because the voltage is carried by ions not electrons, so it's not electricity like you have in the wires in your house.

Note2: As others have pointed out lots of other things can cause these seizures and the mechanisms are not well understood. I used to have a friend who's epilepsy was caused by alcohol.