Search

Purpose: To determine the potential risk of epileptic seizures from wind turbine shadow flicker under various meteorologic conditions. Methods: We extend a previous model to include attenuation of sunlight by the atmosphere using the libradtran radiative transfer code. Results: Under conditions in which observers look toward the horizon with their eyes open we find that there is risk when the observer is closer than 1.2 times the total turbine height when on land, and 2.8 times the total turbine height in marine environments, the risk limited by the size of the image of the sun’s disc on the retina. When looking at the ground, where the shadow of the blade is cast, observers are at risk only when at a distance <36 times the blade width, the risk limited by image contrast. If the observer views the horizon and closes their eyes, however, the stimulus size and contrast ratio are epileptogenic for solar elevation angles down to approximately 5°. Discussion: Large turbines rotate at a rate below that at which the flicker is likely to present a risk, although there is a risk from smaller turbines that interrupt sunlight more than three times per second. For the scenarios considered, we find the risk is negligible at a distance more than about nine times the maximum height reached by the turbine blade, a distance similar to that in guidance from the United Kingdom planning authorities. [ABSTRACT FROM AUTHOR]

Wind turbines are known to produce shadow flicker by interruption of sunlight by the turbine blades. Known parameters of the seizure provoking effect of flicker, i.e., contrast, frequency, mark-space ratio, retinal area stimulated and percentage of visual cortex involved were applied to wind turbine features. The proportion of patients affected by viewing wind turbines expressed as distance in multiples of the hub height of the turbine showed that seizure risk does not decrease significantly until the distance exceeds 100 times the hub height. Since risk does not diminish with viewing distance, flash frequency is therefore the critical factor and should be kept to a maximum of three per second, i.e., sixty revolutions per minute for a three-bladed turbine. On wind farms the shadows cast by one turbine on another should not be viewable by the public if the cumulative flash rate exceeds three per second. Turbine blades should not be reflective. [ABSTRACT FROM AUTHOR]

Purpose: To describe the electroclinical features of subjects who presented with a photosensitive benign myoclonic epilepsy in infancy (PBMEI). Methods: The patients were selected from a group of epileptic subjects with seizure onset in infancy or early childhood. Inclusion criteria were the presence of photic-induced myoclonic seizures and a favorable outcome. Cases with less than 24 month follow up were excluded from the analysis. Results: Eight patients were identified (4 males, 4 females). Personal history was uneventful. All of them had familial antecedents of epilepsy. Psychomotor development was normal in 6 cases, both before and after seizure onset. One patient showed a mild mental retardation and a further patient showed some behavioral disturbances. Neuroradiological investigations, when performed (5 cases), gave normal results. The clinical manifestations were typical and could vary from upward movements of the eyes to myoclonic jerks of the head and shoulders, isolated or briefly repetitive, never causing a fall. Age of onset was between 11 months and 3 years and 2 months. Characteristically, the seizures were always triggered by photic stimulation. Non photo-induced spontaneous myoclonic attacks were reported in 2 cases during the follow-up. Other types of seizures were present at follow-up in 2 cases. The outcome was favorable, even if, usually, seizure control required high AED plasma levels. Since the clinical symptoms were not recognized early, some patients were treated only many years after the onset of symptoms. Conclusion: Among BMEI patients, our cases constitute a subgroup in which myoclonic jerks were always triggered by photostimulation, in particular at onset of their epilepsy. [ABSTRACT FROM AUTHOR]

Purpose: Photosensitivity can represent a serious problem in epilepsy patients, also because pharmacologic treatment is often ineffective. Nonpharmacologic treatment using blue sunglasses is effective and safe in controlling photosensitivity, but large series of patients have never been studied. Methods: This multicenter study was conducted in 12 epilepsy centers in northern, central, southern, and insular Italy. A commercially available lens, named Z1, obtained in a previous trial, was used to test consecutively enrolled pediatric and adult epilepsy patients with photosensitivity. Only type 4 photosensitivity (photoparoxysmal response, PPR) was considered in the study. A standardized method was used for photostimulation. Results: Six hundred ten epilepsy patients were tested. Four hundred (66%) were female patients; 396 (65%) were younger than 14 years. Three hundred eighty-one (62%) subjects were pharmacologically treated at the time of investigation. Z1 lenses made PPR disappear in 463 (75.9%) patients, and PPR was considerably reduced in an additional 109 (17.9%) of them. PPR remained unchanged only in the remaining 38 (6.2%) patients. The response of PPR to Z1 lenses was not significantly influenced by the patients' age, sex, or type of epilepsy. No difference was found between pharmacologically treated and untreated patients. Conclusions: The Z1 lens is highly effective in controlling PPR in a very large number of photosensitive epilepsy patients irrespective of their epilepsy or antiepileptic drug treatment. The lens might become a valid resource in the daily activity of any clinician who cares for patients with epilepsy. [ABSTRACT FROM AUTHOR]

Purpose: The interaction of genetic predisposition and the environment in the development of epilepsy is often discussed, but, aside from some animal reflex epilepsies, little evidence supports such interaction in the development of reflex epilepsy in humans. Methods: We describe the history of a 16-year-old boy in whom photosensitive epilepsy developed after a period of weekly exposures to high-intensity light flashes. Results: Both he and his clinically unaffected monozygotic twin were found to be photosensitive. Conclusions: This case report suggests that some genetic forms of human reflex epilepsy may be elicited by repeated environmental exposure to the appropriate stimulus, similar to some of the stimulus-induced epilepsies seen in animals. [ABSTRACT FROM AUTHOR]

The use of guidelines to prevent the broadcast of epileptogenic television program content has reduced the incidence of seizures in Britain and Japan. Epileptogenic content includes both flicker and patterns. The guidelines for flicker were developed on the basis of a model that related stimulus parameters to the proportion of patients affected. We here extend the model to pattern stimuli. A set of rules is advocated that keeps the level of risk to a consistent minimum and simplifies compliance. We propose that striped patterns that last >0.5 s, occupy more than one fourth the area of the screen, and have bright stripes >50 cd/m2 in luminance be restricted as regards the number of cycles admissible. The guidelines are estimated to protect at least two thirds of susceptible patients. [ABSTRACT FROM AUTHOR]

Summary: Purpose: Based on our previous study that validated efficacies of an adaptive temporal filtering system (ATFS) suppressing a photoparoxysmal response (PPR) elicited by a chromatic flicker stimulation, we further studied ATFS efficacies on PPRs elicited by pattern-flicker stimulation in 13 photosensitive epilepsy patients. Methods: Subjects were 13 photosensitive epilepsy patients (two male and 11 female patients; mean age ± SD, 20.9 ± 8.9 years) who were all sensitive to a flickering geometric-pattern scene. We used a scene consisting of 15-Hz flickering 4 c/deg stripe images lasting for 4 s. With a 14-inch television set 2 m before a subject, we displayed the following video scenes: nonfiltered and filtered flickering-stripe scenes; for the latter, two kinds of ATFSs with mild efficacy and strong efficacy were used. Three flickering-stripe scenes altogether, each of which lasted for 4 s, were given at random with a 10-s interval. Results: A nonfiltered flickering-stripe scene elicited generalized PPRs in all patients; a filtered scene by use of an ATFS with mild efficacy elicited generalized PPRs in six patients (46%), whereas that by an ATFS with strong efficacy exhibited no PPRs. Conclusions: This study, using an ATFS, again shows suppressive efficacy on PPRs elicited by flickering-pattern stimulation. Therefore a series of our studies suggested that ATFS may be useful as a preventive measure for photosensitive seizures triggered by stimulative flickering images from televisions or other displays. [ABSTRACT FROM AUTHOR]

Television (TV) is the most provocative visual stimulus and evokes (first) seizures in susceptible children and adolescents, especially when flickering and patterned images are shown. This has led to the initiative to develop guidelines for broadcasters. The development of new types of TV screens will not remove the need for control of broadcast material. It could be argued that rather than protect the whole viewing audience by application of broadcasting guidelines, only those who are photosensitive should be protected. But maybe we should do both, because most known sensitive patients will benefit from greater safety and will not be dependent on fashionable ideas by commercial broadcasters that are not (yet) familiar with the guidelines. No such guidelines exist for video material, electronic screen games, and the Internet. It would be wise to adopt the guidelines for video material and electronic screen games. [ABSTRACT FROM AUTHOR]