What is the purpose of the Ganzfeld Dome in ERG testing?

• A. To measure pupil size
• B. To stimulate the optic nerve only
• C. To stimulate the entire retina uniformly
• D. To calibrate light intensity

Answer: (C)

In electroretinography, you want to capture the retina’s response to light across its entire surface, not just a small patch. The Ganzfeld Dome achieves this by creating a uniform, diffuse field of light that covers the whole retina at once. That full-field, even illumination activates photoreceptors and the associated retinal cells everywhere, producing an ERG signal that reflects the overall function of the retina. If the stimulation were localized or uneven, the recorded response would be biased toward the stimulated area and wouldn’t represent the retina as a whole. So the dome’s purpose is to stimulate the entire retina uniformly. The other ideas don’t fit: pupil size measurement isn’t what the dome does, ERG targets retinal activity rather than the optic nerve alone, and light-intensity calibration is handled separately.