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Using the visual stimulator, the effect of color on the photoconvulsive response (PCR) was studied in 14 photosensitive patients. When stimuli of 15 c/sec flickers of white, red, yellow, green and blue light of 20 cd/m2 were given to the subjects, generalized PCRs were provoked only by the red-flicker. These PCRs were all inhibited by blue light of 1.9 cd/m2 when given either after the appearance of the PCRs or simultaneously with the red-flicker from the start. When blue light was given after the appearance of the PCRs the latency of appearance of the PCRs in response to the red-flicker showed an inverse relation to the disappearance latency of the PCR in response to the blue light. With blue light of 1 cd/m2, however, inhibition of the PCRs was seen in only 2 cases when it was given after the appearance of the PCR, and in only 1 case when the blue light was simultaneously given with the red-flicker from the start. These results clearly disclosed the following findings: (1) among various colored lights, an excitatory effect on generalized PCR was excitatory effect on generalized PCR was always seen only with red light at 15 c/sec and 20 cd/m2; (2) the PCRs provoked by the red-flicker were inhibited by blue light of 1.9 cd/m2, but not by blue light of 1 cd/m2.

One hundred patients with photosensitive epilepsy were investigated as part of an ongoing follow-up study. Average duration of follow-up was 14 years; mean age at follow-up was 27 years. All patients were EEG investigated using a standard technique of intermittent photic stimulation (IPS). The presence of a photoparoxysmal response (PPR) or a degraded PPR indicated the presence of photosensitivity. Seventy-seven patients became seizure free. Of the untreated patients, photosensitivity disappeared in 14 patients but was present in 32 patients. Of the patients who were treated, 31 showed evidence of PPRs or degraded PPRs, but 23 patients no longer showed evidence of photosensitivity. Thirty-two mothers had 67 children during the follow-up period. Thirteen have so far proved to be sensitive to IPS in the laboratory and four have also had photosensitive seizures induced in the outside environment. Nine of the children have been found not to be photosensitive nor have they had seizures. This study suggests that photosensitivity persists in at least two thirds of patients with photosensitive epilepsy and that valproate is effective in controlling this photosensitivity.