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 When I first saw a light/sound system in 1990, it had a seizure warning, saying persons with epilepsy problems should not use the system. As far as I knew I had no such problems, so I used the system and many more since. When we began selling light/sound systems under our own brainwave synchronizer name, we used warnings copied from other manufacturers, assuming they knew what they were doing. Over the years, I have researched the light/sound, seizures and epilepsy subject quite a bit, and, while still falling far short of having real medical knowledge, and possessing credentials neither in the medical nor legal fields, I believe I understand a lot about the risks involved. This article is an attempt to make this information generally available, as well as to provide sources for additional inquiry for those interested. It will provide a better understanding for most readers, but I would encourage any readers who need authoritative information to follow up on the references or to consult with a legal or medical professional as appropriate. The main source for the information given here is the definitive book on photosensitive epilepsy, titled appropriately "Photosensitive Epilepsy" (ref 1). Several other sources were used for tidbits here and there and are also listed as references. A lot of this information is also found on the www.brainwave synchronizer.com web site. Some Definitions and Probabilities To set the stage for some of the following discussion, here are some definitions, descriptions and statistics. Seizure A seizure is a paroxysmal (sudden, spasmodic) self limited (stops by itself with no outside assistance) event caused by an excessive electrical discharge of the central nervous system. There are several varieties of seizures, from a simple absence seizure, where the subject just "blanks out" for a short period, to the most dramatic, the Tonic-Clonic (formerly called Grand Mal) seizure, usually characterized by falling, muscles stiffening, body extremities jerking and twitching for a small number of minutes, and temporary loss of consciousness. Seizures are usually harmless, with any injury coming from falling or hitting a hard object, although serious consequences including death are possible in unusual circumstances. About 8.8% of the general population (1 person in 11) will experience a seizure at some point in their lives (although most seizures are not Tonic-Clonic). If you are in a safe place, seated or lying down, you have some protection from the major cause of injury from a seizure, namely falling and striking a hard object. Light/sound sessions should always be experienced while seated or lying down in a safe place, even after you are thoroughly convinced that you are not photosensitive. This assists the relaxation process as well as giving some protection from injury in the unlikely event of a seizure. Epilepsy Epilepsy is a condition characterized by recurrent seizures. The frequency of epilepsy is about 0.65% in the general population (1 person in 153). Thus epilepsy is much less common than isolated seizures, and a patient is usually not diagnosed as epileptic until a second seizure. Photosensitive Epilepsy Photosensitive Epilepsy (PSE) is a relatively rare condition, affecting approximately 1 person in 4,000. Persons with this condition can have seizures precipitated by flickering lights, such as those produced by a light/sound machine. Photosensitivity is rare enough in the general population that most books on seizures and epilepsy do not even mention it. Reference (1) is the only thorough treatment in the literature. If you look up photosensitive epilepsy on the web, you will find several sites that got all their information from this source. Most persons with photosensitive epilepsy have a first seizure during their teenage years (75% by age 20). About half of initial seizures are induced by watching television. Some persons who are susceptible during their teenage years outgrow the condition, about 25% by age 25. As a result, adults over age 25 who have never had a seizure have about 1 chance in 20,000 of being photosensitive and not knowing it. So for a person who has not had a seizure, the likelihood of being photosensitive varies from 1 in 4,000 for children to 1 in 20,000 for adults over 25. Even if a person has never had a seizure, there is a small chance that they are photosensitive and a light/sound session could cause a seizure. In spite of the more inclusive summary warning generally given on light/sound systems, even if a person has problems with epilepsy, there is only about a 5% chance that he/she is photosensitive. Such persons could check with a neurologist to find out if they are photosensitive, and may be able to use light/sound without seizure concerns. Susceptibility to Seizures A persons susceptibility to having photosensitive seizures is influenced by several factors. Genetics plays a definite role, sex is a factor, and the persons general physical condition and current physical state also play a part. Photosensitivity is more prevalent among females, about 1.69:1. A photosensitive mother has a one in four chance of having a photosensitive child, and having a photosensitive sibling raises the odds of photosensitivity. Evidence of photosensitivity passing through the father's genes is inconclusive. Physical factors that have been suspected as an influence are tiredness, influenza, alcohol and premenstrual state. A large part of the discussion in ref (1) is devoted to television watching, because so many man-hours are devoted to this pastime and because it seems to be a necessary part of life for so many people. It is interesting that TV manufacturers do not find it necessary to post seizure warnings on their products, which cause far more seizures than light/sound machines. Light/sound machines are probably stronger seizure triggers than TV sets, because of the regularity of the stimulation, but the population using light/sound is minuscule compared to the one using TV, so relatively little research has been devoted to comparisons. Triggering Seizures The types of photic stimulation that can cause photosensitive seizures cover a wide gamut. Historically, the story of a seizure caused by watching flickering light from a potters wheel, reported by Apuleius in the book Apologia written about AD125, is debunked in ref (1), as is the story of a seizure induced by viewing the sun through trees on a tree- lined road. Ref (1) reports that the first reliable reference to PSE is Gowers, Epilepsy and Other Chronic Convulsive Diseases, Their Causes, Symptoms and Treatment (1885). The seizure type most often provoked by photosensitivity is the tonic-clonic (formerly called grand mal) seizure. Self-induced photosensitive seizures are possible, by viewing a light source and waving the hand with fingers outstretched rapidly across the eyes. Some persons can have seizures provoked by closing their eyes. PSE seizures are more likely with the eyes closed, probably because of the lights being diffused across the entire retina. Some persons are sensitive to certain visual patterns, but most PSE appears to be from flickering lights - intermittent photic stimulation (IPS). Besides TV, the sun reflecting from water, windshield wipers, discotheques and many other sources are mentioned in ref (1). The book was published in 1994, a new edition done today might mention light/sound machines. Flash rates that can cause seizures vary widely, but the optimum rate to induce PSE is between 10 and 25 Hertz, with the peak between 15 and 20. The length of the exposure used when testing for PSE has varied from two seconds to 20 minutes. It is generally agreed that a longer exposure increases the probability of a PSE response. Medina and Leston (1990) compared IPS with and without a diffuser, and found that the results with the eyes open and a diffusion screen could be as marked as those with the eyes closed. There is a lot of evidence that a PPR response (see next paragraph) is more likely in the 2 second interval following eye closure. A background illumination seems to reduce the PPR likelihood. Photoparoxysmal Responses A response to IPS can be measured by EEG equipment, usually at a lower stimulation level than that required to evoke a seizure, and this is used in testing for susceptibility to PSE without inducing seizures. A photoparoxysmal response (PPR) is a discharge evoked by IPS which is bilateral and recorded simultaneously from all areas of the scalp. It is usually a 3 to 3.5 hertz spike wave discharge. This response has been found to be associated with PSE, and is used by researchers in testing for PSE. Ref (1) goes into great detail in discussing the various types of PPR waveforms. PPRs which consist of 3 hz spike-wave discharges are very rare in normal subjects. An EEG test for a PPR response is the accepted technique for testing for photosensitivity. Color There has been a lot of discussion of the effect of the color of the stimulating lights in evoking a PPR or seizure. Several researchers have reported increased sensitivity to red light, although the literature reported in ref (1) is by no means unanimous in this conclusion. A PPR response is more likely with the eyes closed, and the eyelids act as a red filter, reducing the effect of blue or green light. Some researchers have concluded that this factor alone accounts for the reported increased sensitivity to red light. According to ref (1), putting a red filter in front of open eyes does not increase EEG discharges. Harding and Jeavons (ref 1) conducted their own study and concluded that the color of the light did not significantly alter the presence of occipital spikes. Reading the section on color in ref (1) pages 57-61 left me with the feeling that red may be somewhat more provocative, but the case is certainly not clear. There is no dispute that blue is the least provocative color, definitely less provocative than white. It is interesting to note that incandescent bulbs are not white, but have a strong bias towards the red end of the spectrum, whereas white LEDs have a very strong blue component and relatively little red. Advice to Photosensitive Patients Aside from drug treatment, therapy for the photosensitive patient is to avoid the stimulus. The drug sodium valproate has few side effects and is effective in preventing photosensitivity in most patients. A photosensitive person should avoid flickering lights and, if accidentally exposed, should cover one eye while getting away from the stimulation. Obviously such persons should avoid light/sound machines. In watching TV, the following precautions should be observed: - View TV in a well lit room at a distance of 6 feet or more. - A small illuminated lamp should be placed on the TV. - Do not approach the TV for adjustments. If it is necessary to do so because the remote control is lost, cover one eye. - Polarized sunglasses outdoors on sunny days are of assistance. Ordinary colored glasses are useless. Treatment of Epilepsy Drugs are available that reduce the frequency of seizures in persons with uncontrolled epilepsy. These drugs usually have undesirable side effects. Furthermore, initiating drug treatment and hence establishing the diagnosis of epilepsy will have significant consequences for a person's life. It may restrict their driving privileges and can eliminate them from consideration for certain jobs such as pilot, commercial diving or commercial automobile or truck driving. It can make obtaining health and life insurance difficult. It often attaches a social stigma, which can have profound negative effects on self-esteem and social opportunities. For these reasons, most neurologists and epileptologists (a neurologist with a specialty in epilepsy) are reluctant to diagnose epilepsy from a first seizure unless the risk of recurrence is high. A person who has experienced a first seizure should be examined by a physician, to determine if any injury has occurred and if treatment for epilepsy is appropriate. Except in unusual circumstances (see First Aid for Seizures below) it is not necessary or even desirable to visit an emergency room, as emergency room physicians often do not know how to deal with seizures. It is better to see a neurologist, preferably an epileptologist, as soon as possible. The neurologist will conduct several tests to see if there is any underlying cause for the seizure that should be treated, or if it was just a single seizure triggered by the flashing lights. If flickering lights and photosensitivity was the cause of the seizure, then the patient knows he/she should avoid flickering lights in the future, but probably no other life style changes will be required and the diagnosis of epilepsy is not appropriate. If you or anyone you know has a first seizure while using a light/sound machine, and drugs are prescribed without finding an underlying physiological cause for the seizure, you may want to get a second opinion. In some states (currently California, Delaware, Nevada, New Jersey, Oregon and Pennsylvania), a physician examining a person who has epilepsy is required to report to the department of motor vehicles, and the individuals drivers license may be taken away until the doctor reports that the individual can drive safely. This is another reason to avoid emergency room physicians, many of whom are not sure how to deal with seizures, and may incorrectly diagnose epilepsy just to play it safe. A seizure is said to be provoked if it is triggered by an external influence, such as alcohol, drugs or flashing lights. It is unprovoked if it had no such external trigger, but arose spontaneously from within the subject. There is some controversy in the medical community on the desirability of treating a first unprovoked seizure. See the web site www.seizures.net/Articles/new onset.html for an excellent coverage of this subject. I think there is good agreement that a first provoked seizure should not be treated, unless an underlying physiological problem is found. Ref (1) page 137 says that if a person has a seizure evoked by TV or other flickering light source, but the EEG is normal and spike-wave discharges are confined to IPS, then drugs are not appropriate. We have seen a case where a seizure patient was taken to an emergency room (UCLA no less) and drugs were prescribed in just such a case. Side effects of the continued drug treatment were a problem for this person two years later. While we do not know for sure, this is probably a case of medical malpractice. In our legal system, the device causing the original seizure is still held responsible, on the grounds that otherwise the patient would have never been exposed to the malpractice. By the way, the seizure in this case was not caused by a brainwave synchronizer device. But the case pointed out clearly to us that the treatment of a seizure can be far more harmful than the seizure itself. First Aid for Seizures This material is from "The Epilepsy Handbook" (ref 2), copied by permission. These procedures are for Tonic-Clonic (formerly called Grand Mal) seizures, the kind most commonly caused by photosensitivity. During the Seizure: The person may fall, become stiff and make jerking movements. The person's complexion may become pale or bluish. - DO help the person lie down and put something soft under the head. - DO remove any eyeglasses and loosen any tight clothing. - DO clear the area of sharp or hard objects. - DO NOT force anything into the person's mouth. - DO NOT try to restrain the person. You cannot stop the seizure. After the Seizure: The person may awaken confused and disoriented. - DO turn the person to one side to allow saliva to drain from the mouth. - DO arrange for someone to stay nearby until the person is fully awake. - DO NOT offer the person any food or drink. Calling for Help: (Usually not necessary) Call 911 or the local police if... - The person does not start breathing within 1 minute after the seizure ends (begin mouth to mouth resuscitation). - A generalized tonic-clonic seizure lasts more than 2 minutes. - The person has one seizure right after another. - The person is injured. - The person requests an ambulance. Conclusions for Light / Sound Dealers The likelihood of a seizure from a light/sound experience is small for persons who have not had a seizure before. But it is possible, and the person involved should have the opportunity to make his own informed decision about taking the risk. Persons purchasing light/sound equipment are warned by labels on the equipment and in manuals, although the standard warning targeting persons who already know of their condition is not adequate. We are changing the brainwave synchronizer warning from "do not use this device if you have epilepsy problems" to "this device can cause seizures in photosensitive persons, you may be one and not know it". If you give demos or run a spa, you are giving people sessions without showing them the warnings on the manual. It is your responsibility to spread the warning in this situation, and let the individual make his own informed decision. If you are running a spa, signed waivers are recommended. See your attorney for proper wording. References 1) Harding and Jeavons, 1994, Photosensitive Epilepsy, London, MacKeith Press. 2) Gumnit, 1995, The Epilepsy Handbook, The Practical Management of Seizures, New York, Raven Press Ltd. 3) Medina and Liston, 1990, Photosensitive Epilepsy, Electrophysiological Aspects. Medicina, 50, 9-15. Links What is epilepsy? (Includes a first aid section) www.lhsc.on.ca/eeg/epilepsy.htm Photosensitivity www.epilepsynse.org.uk/pages/info/leaflets/photo.html Driver licensing www.efa.org/advocacy/drivelaw/driving.html Initial management of new onset seizures, to treat or not to treat? Www.seizures.net/Articles/new_onset.html * * * * * * * * * * Ray Wolfe, CEO of Microfirm, Inc., and co-owner Snezana Zdravkova converted their company from embedded microprocessor applications to designing and manufacturing light and sound instruments in 1990. Today, they are one of the world's leaders in producing quality AVS products. Copyright Ray Wolfe / 2000. |
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