Figure 8. Dark adaptation of the b-wave, monitored with the brighter test flash, and conversion to equivalent background intensity.

Dark adaptation recovery for subject A.M.C., measured using the brighter fixed flash intensity of 0.1 Td s, for bleaching exposures of six different strengths: 1.9, 5.4, 10, 26, 45 and 96%. A, normalized amplitude of the b-wave response, before, and up to 35 min after, cessation of each exposure. Response amplitudes have been measured at the peak and normalized to the mean amplitude of the pre-bleach and fully recovered responses. Each bleach was delivered two or three times (generally in experiments on different days) using the same exposure; however, the pupil size varied from day to day and so the average bleach levels are given. Each symbol plots the average of the normalized amplitudes recorded during an interval of 1 min; hence, with 16 flashes per interval, per bleach, each point has been averaged from up to 48 flash presentations. The grey vertical lines indicate the timing of bleach delivery. The curves convert the equivalent background intensity traces plotted in B into desensitizations, using eqn (4). B, the points in A have been converted into ‘equivalent background intensities’ using eqn (5) with parameter values determined from the Weber's Law relation, eqn (3) fitted to the light adaptation results in Fig. 6 for this test flash intensity (0.1 Td s), i.e. with I₀= 0.22 Td and n = 0.88. Measurements that would have transformed to values outside the vertical limits of the panel have been plotted at those limits. The dashed horizontal line indicates I₀, and the transformed symbols are most reliable over the region of ∼1 log₁₀ unit above and below this level. The curves in B plot the decay of equivalent background intensity I_equiv(t) predicted by eqn (6), using the values of I_S2(0) reported in Table 1. These curves were then transformed into the curves in A by substitution into eqn (4) using the values above for I₀ and n.