Fig. 1. Fast oscillation (FO) recoding from a normal eye with 12 cycles of dark and light intervals (75 seconds each). The dark-peak (DP) and light-trough (LT). The FO amplitude was calculated from the average of the peak-to-trough ratios from each of the dark-light cycles. The FO peak-to-trough ratio is computed from the amplitude of the DP divided by the amplitude of the LT.