Circadian rhythm of human electroretinogram.

In order to ascertain the presence of circadian rhythm in the electrical responses of the retina, scotopic electroretinogram (ERG) evoked mainly by light flash stimulus was recorded consecutively in 14 normal healthy subjects during a 24-hour period. The ERGs were measured at 6, 12, 18 and 24 o'clock. Both a- and b-waves were analyzed. The a-wave amplitude of all subjects studied showed no circadian rhythm. By our criteria, the b-wave amplitude showed circadian rhythm in 8 of the 14 subjects. The minimum amplitude of the b-wave was seen at 6 o'clock. The amplitude of the b-wave was significantly higher at 12 o'clock when compared with the amplitude at 6, 18 and 24 o'clock. This tendency was repeatedly observed. The presence of circadian rhythm in the scotopic b-wave was, therefore, suggested. This rhythm had a good correlation with the circadian rhythm of dopamine beta-hydroxylase in the serum and no correlation with the corticosteroid level in the serum. The possibility of circadian rhythm in the human ERG should be taken into consideration for routine clinical application.