The mfERG stimulus pattern was presented on a 19-inch RGB (red-green-blue) monitor (model GDM-500PS; Sony, Tokyo, Japan), and the mfERG program (VERIS 4.1; EDI, San Mateo, CA) was run on a computer (Macintosh G3; Apple Computer, Cupertino, CA). The mfERG was measured by using the luminance-modulated global-flash mfERG paradigm.
29 In this paradigm, each m-sequence stimulation cycle consisted of four video frames (each frame lasts 13.3 ms, with a 75-Hz frame rate). There was an initial multifocal pattern with 103 hexagons, scaled with eccentricity (scale factor, 10.46), and each hexagon was either bright or dark according to a pseudorandom binary m-sequence. After the multifocal flash, there was a dark frame (0.04 cd · s/m
2, i.e., 3 cd/m
2 per frame), a full-screen global flash (2.16 cd · s/m
2, i.e., 162 cd/m
2 per frame), and a second dark frame before the next m-sequence stimulation. The average luminance of the multifocal flashes was approximately 1.11 cd · s/m
2 (i.e., 83 cd/m
2 per frame) and the background was also set to this luminance
(Fig. 1) .
Recordings were divided into 16 slightly overlapping recording segments. The recording time for each stimulation cycle was approximately 8 minutes, with a 2
13 − 1 binary m-sequence. Four different stimulus–contrast conditions in the global-flash paradigm were performed, and the luminance difference of the multifocal flashes were set at 2.12, 1.42, 1.08, and 0.62 cd · s/m
2 (Fig. 1B) . The order of the four stimulus conditions was randomized across subjects, to distribute the effect of fatigue across conditions.