Wave 2 in a scotopic ERG corresponds to which wave label?

Wave 2 in a scotopic ERG corresponds to which wave label?

• A. A-wave in photopic ERG
• B. B-wave in scotopic ERG
• C. B-wave in photopic ERG
• D. A-wave in scotopic ERG

Answer: (B)

In dark-adapted (scotopic) ERG, the first deflection you see is the negative A-wave, produced by the photoreceptors (primarily rods). The next, positive deflection—the second wave—is generated by the inner retina, mainly the rod bipolar cells (with support from Müller cells). So the second wave under scotopic conditions is the B-wave in scotopic ERG. For contrast, in photopic (cone) ERG you still have A- and B-waves, but the B-wave there reflects cone-driven inner-retinal activity, not the rod-driven response seen in scotopic testing.

In dark-adapted (scotopic) ERG, the first deflection you see is the negative A-wave, produced by the photoreceptors (primarily rods). The next, positive deflection—the second wave—is generated by the inner retina, mainly the rod bipolar cells (with support from Müller cells). So the second wave under scotopic conditions is the B-wave in scotopic ERG. For contrast, in photopic (cone) ERG you still have A- and B-waves, but the B-wave there reflects cone-driven inner-retinal activity, not the rod-driven response seen in scotopic testing.