A Study of the Effect of Color Photostimulation from a Cathode‐ray Tube (CRT) Display on Photosensitive Patients: The Effect of Alternating Red–Cyan Flicker Stimulation

Abstract

Summary: Purpose:In an attempt to establish evidence for developing better guidelines for the production of animation programs that would not induce photosensitive seizures in Japan, we evaluated the effects of red flicker, alternating red/cyan (complementary color to red) flicker stimuli, and of contrast between the red and cyan frames from a cathode-ray tube (CRT) display in photosensitive patients.Methods: We studied 35 photosensitive patients. They were exposed to seven types of flicker. The first three types were alternating red/cyan flicker (R/C) with the luminance of cyan set at three different levels, high, equal, and low luminance (65, 20, and 16 cd/m 2 , respectively) relative to the red (20 cd/m 2 ). The following four types were red, cyan, yellow, and magenta flicker stimuli. EEGs were recorded while the patients watched these stimuli on a CRT display.Results: Rates of photoparoxysmal response (PPR) provocation were 11.4, 13.7, and 14.0% with high-, no-and lowcontrast R/C flicker, respectively, and 3.7% with red flicker. The differences between red and each of the other R/C flicker stimuli were all statistically significant (p<0.05, 0.01, 0.01). No significant differences were found between the effects by each of the three levels of contrast in alternating R/C flicker (p > 0.05).Conclusions: These findings suggest that alternating R/C flicker is more provocative than simple red flicker, and that contrast between frames of different colors may play some role in the effects of alternating flicker stimuli from a CRT display in photosensitive patients. Therefore, caution against the use of the combination of red and cyan, in addition to the red flicker stimulus, should be included in any guidelines drawn up to prevent photosensitive seizures.

Characterizing the Patterned Images That Precipitate Seizures and Optimizing Guidelines To Prevent Them

“…Gratings with red/green stripes that do not differ in luminance are not epileptogenic, at least for patients with normal colour vision (2). It is not known whether isoluminant patterns of red/cyan stripes are epileptogenic, although red/cyan isoluminant flicker is known to be so (4). Given the available evidence, it will be assumed for simplicity that the epileptogenic properties of a pattern depend on the luminance contrast across its stripes without respect to chromaticity.…”

“…On later investigation, 560 of these viewers were shown to have had epileptic seizures, and 76% of these patients had no previous history of epilepsy (3). The use of alternating red and blue backgrounds on successive frames was implicated in precipitating the seizures (4).…”

Photosensitivity and visually induced seizures: review

“…An induced colour contrast effect possibly plays a role as well, resulting in colour combinations that are more likely to elicit PPR than others. Red and cyan stimulation appears to have a synergistic effect [42] in provoking a PPR, in such a way that each colour amplifies the sensitivity to the other. Red and green isoluminance patterns did not evoke any epileptiform activity [43] and did not affect the latency and amplitude of the visual evoked potential [34 ].…”

Optical countermeasures against CLOS weapon systems

“…Red-blue flicker is most provocative below 30 Hz [36][37][38] . The induced cortical excitation manifests itself in a chromatic flash VEP (visually evoked potential), which is the primary response of the target to the chromatic flicker and can be measured on a EEG (electroencephalogram).…”