An Explanation for Using Tinted Blue Overlays When Stimulating with White Light
By David Siever, CEO of MindAlive, Inc.
Because photic induced seizures involving those aged from 5 – 24 years of 1/4000 has been reported by Newmark and Penry (1979) and Jeavons, Bishop and Harding (1986), care must be taken when delivering photic stimulation to children. Physiological photic stimulators generally used to induce seizures employ a Xenon strobe light that reaches maximum brightness within 50 micro-seconds at intensities of 10,000-300,000 lux. Carterette and Symmes (1952) first reported that red-flicker provoked an increased photoconvulsive response (PCR) relative to other wavelengths. Since then, this finding has been reported by Bickford (1953); Marshall (1953); Pantelakis (1962); Kojima (1963); Brausch and Ferguson (1965); Harley (1967); Takahashi and Tsukahara (1972a, 1973). It has also been reported by Carterette and Symmes (1952); Brausch and Ferguson (1965); Buskirk (1952); Marshall et al (1953); Bickford (1954); Asano and Umezaki (1965); Maruyama (1968); Takahashi and Tsukahara (1972b) and Harley (1967) that red-removing eyeglasses or contact lenses afforded clinical relief to patients with photogenic epilepsy. Kasteleijn-Nolst Trenite (1989) found that in 100 PCR participants, 81 showed sensitivity with eyes closed while 66 were sensitive with their eyes opened. Harding and Jeavons (1994) found that peak PCR sensitivity occurs from 15 – 20 flashes per second. Takahashi and Tsukahara (1976) measured IPS induced PCRs under controlled lighting conditions. They observed that PCRs were most frequently induced with red light stimulation from 15 – 20 Hz and that it was superior in producing PCRs than stroboscopic (white) light. In all 14 cases generalized PCRs of sharp and wave and spike and wave complex were induced. They also found that 20 cd/m2 were inhibited by blue light of 1.9 cd/m2.
All of these studies used a brief, intense flash pulse. Ruuskanen-Uoti (1994) reported ona person who developed seizures while using a “light and sound” machine utilizing square wave stimulation delivered by red light emitting diodes (LEDs).
Brief, intense flashes produce harmonic activity in the brain, Van der Tweel and Verduyn(1965) whereas sine wave stimulation produces a sine-like response (insignificant harmonic activity). Van der Tweel and Verduyn (1965), Townsend (1973), Donker (1978) and Regan (1965) all agree that sine-wave modulated light eliminates the problem of light intensity from a Xenon strobe increasing with frequency and the harmonics generated within the neo-cortex at frequency multiples much higher than the fundamental at times. It has been our observations that square wave LED flashing at 7 Hz can produce strong harmonics between 20 and 40 Hz. Of these sine wave stimulation studies, the concern of inducing seizures is completely omitted from the studies. In the raw EEGs shown in the studies, there are no signs of epileptiform activity nor any discussion about it.
To address the concerns of eliciting a photic induced seizure, the lightframes used had a slowed turn-on and -off time of about 15 msec. The light emitted from the lightframes was white light produced by incandescent bulbs over which was a translucent plastic sheet that was tinted a shade of light blue. (Originally published in The Journal of Neurotherapy Vol 4, #2. By David Siever).
Published by permission of Dave Siever. All rights reserved.