Pseudorandom full-field electroretinograms reflect different light adaptation mechanisms.

Purpose: To investigate the magnitude and time course of pseudorandom ffERG during light adaptation.

Methods: Ten healthy subjects (26 ± 10.1 years) underwent 20 min of dark adaptation, and then the ffERG was evoked by pseudorandom flash sequences (4 ms per flash, 3 cd.s/m) driven by m-sequences (2-1 stimulus steps) using Veris Science software and a Ganzfeld dome over a constant field of light adaptation (30 cd/m). The base period of the m-sequence was 50 ms. Each stimulation sequence lasting 40 s was repeated at 0, 5, 10, 15 and 20 min of light adaptation. Relative amplitude and latency (corrected by values found at 0 min) of the three components (N1, P1, and N2) of first-order (K) and first slice of the second-order (K) kernel at 5 time points were evaluated. An exponential model was fitted to the mean amplitude and latency data as a function of the light adaptation duration to estimate the time course (τ) of the light adaptation for each component. Repeated one-way ANOVA followed by Tukey post-test was applied to the amplitude and latency data, considering significant values of p < 0.05.

Results: Regarding the K ffERG, N1 K, P1 K, and N2 K presented an amplitude increase as a function of the light adaptation (N1 K τ value = 2.66 min ± 4.2; P1 K τ value = 2.69 min ± 2.10; and N2 K τ value = 3.49 min ± 2.96). P1 K and N2 K implicit time changed as a function of the light adaptation duration (P1 K τ value = 3.61 min ± 5.2; N2 K τ value = 3.25 min ± 4.8). N1 K had small implicit time changes during the light adaptation. All the K components also had nonsignificant changes in amplitude and implicit time during the light adaptation.

Conclusions: Pseudorandom ffERGs showed different mechanisms of adaptation to retinal light. Our results suggest that K ffERG is generated by retinal mechanisms with intermediate- to long-term light adaptation, while K ffERG is generated by retinal mechanism with fast light adaptation course.