Where is the negative reference electrode placed during an ERG recording?

Where is the negative reference electrode placed during an ERG recording?

• A. On the eyelid
• B. Near the eye, forehead, or temple
• C. On the chin
• D. On the ear

Answer: (B)

In ERG, the reference electrode is placed close to the active site so the recorded difference mainly reflects retinal activity rather than distant noise. Placing it near the eye—on the forehead, temple, or just around the orbital area—keeps the reference in the same electrical environment as the recording electrode, minimizing impedance differences and common-mode noise. Putting the reference on the eyelid would introduce motion and contact instability; on the chin or the ear would place it in a very different electrical field, increasing artifacts and reducing signal specificity.

In ERG, the reference electrode is placed close to the active site so the recorded difference mainly reflects retinal activity rather than distant noise. Placing it near the eye—on the forehead, temple, or just around the orbital area—keeps the reference in the same electrical environment as the recording electrode, minimizing impedance differences and common-mode noise. Putting the reference on the eyelid would introduce motion and contact instability; on the chin or the ear would place it in a very different electrical field, increasing artifacts and reducing signal specificity.