Wavelength Dependence of Photoparoxysmal Responses in Photosensitive Patients with Epilepsy


Address correspondence and reprint requests to Dr. Y. Takahashi at Department of Pediatrics, Gifu University School of Medicine, 40 Tsukasa-machi, Gifu 500-8705, Japan. E-mail: yukito@cc.gifu-u.ac.jp


Purpose: We tried to specify the relation between the photoparoxysmal response (PPR) and the wavelength spectra of flashing light in various photosensitive epileptic syndromes in the physiologic state.

Methods: Intermittent photic stimulation (IPS) by a Grass PS22 photic stimulator was performed with wavelength-specific optical filters in photosensitive patients with epilepsy (idiopathic generalized epilepsy, IGE; hereditary dentatorubral-pallidoluysian atrophy, DRPLA) and photosensitive subjects without epilepsy.

Results: Five of 19 normal trichromat patients with IGE and an IGE patient with deuteranomaly showed wavelength-dependent PPRs. The wavelength-dependent PPRs were elicited only by IPS containing wavelength spectra ∼700 nm in the normal trichromat patients. Two of four patients with DRPLA showed wavelength-dependent PPRs, and two other DRPLA patients showed quantity-of-light-dependent PPRs. Quantity-of-light-dependent PPRs are elicited by IPS containing more than a certain quantity of light, independent of the wavelength composition of the flashing light. Two of five subjects without epilepsy showed wavelength-dependent PPRs.

Conclusions: There are wavelength-dependent and quantity-of-light-dependent pathophysiologic mechanisms for eliciting PPRs by low-luminance IPS. Consideration of the quantity and wavelength composition of light from electronic screens will lead to the prevention of photosensitive seizures induced by electronic screen games.