Where is the ground electrode placed during an ERG recording?

Where is the ground electrode placed during an ERG recording?

• A. Forehead
• B. Ear
• C. Nasal bridge
• D. Lateral canthus

Answer: (B)

In ERG testing, the ground electrode serves as a stable reference that helps suppress noise and complete the electrical circuit for the retinal signal. Placing it on the ear (usually the earlobe or mastoid area) provides a relatively stable impedance, is distant from the muscles around the eyes, and minimizes contamination from blinking or facial movements. The other sites near the eyes—the forehead, nasal bridge, or outer corner of the eye—are more prone to muscle artifacts and ocular movement, which can distort the tiny retinal signals. So the ear is chosen to give a cleaner, more stable baseline for the recording.

In ERG testing, the ground electrode serves as a stable reference that helps suppress noise and complete the electrical circuit for the retinal signal. Placing it on the ear (usually the earlobe or mastoid area) provides a relatively stable impedance, is distant from the muscles around the eyes, and minimizes contamination from blinking or facial movements. The other sites near the eyes—the forehead, nasal bridge, or outer corner of the eye—are more prone to muscle artifacts and ocular movement, which can distort the tiny retinal signals. So the ear is chosen to give a cleaner, more stable baseline for the recording.