Question
A wave in ERG is due to activity of:
| A. |
Pigmented epithelium
|
| B. |
Rods and cones
|
| C. |
Ganglion cell
|
| D. |
Bipolar cell
|
Show Answer
|
Correct Answer » B
Explanation
|
|
– Electroretinogram (ERG) records retinal electrical responses to light.
– Each ERG wave reflects activity from specific retinal cells.
– The a-wave is the initial negative deflection.
– It’s generated by hyperpolarization of photoreceptors (rods & cones) when exposed to light.
– Thus, the a-wave reflects outer retina function.
– Incorrect options:
– Retinal pigment epithelium produces the c-wave, not the a-wave.
– Ganglion cells contribute to pattern ERG, not the a-wave.
– Bipolar cells produce the b-wave, a positive deflection following the a-wave.
Clinical correlations:
– Retinitis pigmentosa → ↓ a-wave (photoreceptor damage)
– Congenital stationary night blindness → normal a-wave, ↓ b-wave
– Central retinal artery occlusion → ↓ b-wave
