Which waves are found on a scotopic ERG?

Which waves are found on a scotopic ERG?

• A. a, b, c
• B. a, b, d
• C. a, c, d
• D. b, c, d

Answer: (A)

Scotopic ERG measures rod-driven responses in the dark. The early negative deflection, or a-wave, comes from photoreceptors, while the subsequent positive deflection, the b-wave, reflects activity of ON-bipolar cells (with some contribution from Müller cells). In addition, with sufficiently long-duration stimuli, a slower positive response from the retinal pigment epithelium–photoreceptor interaction—the c-wave—can appear even under dark-adapted conditions. The d-wave is an OFF response seen after light offset and is not a standard feature of the immediate scotopic response with typical brief flashes. So the waves you can observe in a scotopic ERG include a, b, and, under appropriate stimulus conditions, the c-wave.

Scotopic ERG measures rod-driven responses in the dark. The early negative deflection, or a-wave, comes from photoreceptors, while the subsequent positive deflection, the b-wave, reflects activity of ON-bipolar cells (with some contribution from Müller cells). In addition, with sufficiently long-duration stimuli, a slower positive response from the retinal pigment epithelium–photoreceptor interaction—the c-wave—can appear even under dark-adapted conditions. The d-wave is an OFF response seen after light offset and is not a standard feature of the immediate scotopic response with typical brief flashes. So the waves you can observe in a scotopic ERG include a, b, and, under appropriate stimulus conditions, the c-wave.