Two different types of optical filters were tested in 20 photosensitive epileptic patients for ability to inhibit photoparoxysmal response (PPR) and seizures, in a study at Gifu Prefectural Gifu Hospital, Japan. One filter reflected long-wavelength red light selectively (wavelength dependent) and the other absorbed light in the visible spectrum evenly (quantity of light-dependent). Both filters individually provided insufficient inhibition of PPR (<50%) while using conventional strobe intermittent photic stimulation (IPS), whereas compound filters (both types) inhibited PPR by 90% for IPS and 95% for photic stimulation using cathode ray tubes (CRT). Compound optical filters do not block the chromaticity of emissions from TV-CRT, and may be used to prevent TV-induced seizures in photosensitive persons. [1]

COMMENT. The use of optical filters to prevent photosensitive epilepsy is not a novel suggestion. Glasses with a neutral filter were introduced some 50 years ago by Bickford RG et al [2] at the Mayo Clinic. The use of compound filters may lessen the risk of seizures or epilepsy onset in persons with latent photosensitivity when viewing TV or using personal computers. Photosensitivity is a common problem affecting 4 to 9% of the population. It has an autosomal dominant inheritance and a strong age-dependent penetrance. In recent years, the incidence of photosensitive reflex epilepsy has escalated as an environmental hazard, mainly associated with the introduction of electronic devices, particularly video games. A mass seizure outbreak in Japan was caused by an animated TV program for children, ‘Pocket Monsters’ [3]. The onus for prevention should be placed more on the manufacturer of hazardous video games and regulatory agencies than on the consumer, however.