Electroretinogram

The retina in each of our eyes contains both rod cells and cone cells. Our rod cells allow us to see at night, and our cone cells help us see in daylight. An electroretinogram (ERG) is a test that measures the retina’s electrical activity in response to light.

What Is an Electroretinogram (ERG)?

An ERG is a noninvasive procedure used to diagnose a wide range of problems with the retina, including:

• Acquired eye disorders.

• Drug toxicity-related eye injuries.
• Foreign bodies.
• Inherited eye conditions.

The ERG may look different depending on your child’s symptoms, abilities, and age.

• For most patients, we use a skin electrode which is placed on the skin under the eyes.

• For some patients, we use a thread electrode, which is a tiny thread placed under the lower eyelid. It isn’t painful, but it might feel like having an eyelash in your eye.

These electrodes differ from the ones used in visual evoked potentials (VEP) testing.

To check your child’s eyes, we will show them a series of flashing lights from a handheld flashlight. The lights may be blue, red, or white and can be fast or slow. The lights are not painful, just very bright.

Sometimes we need to wake up the rod cells, so we may have your child sit in a very dark room for 20 minutes. We are happy to play music or provide games while your child waits, if you’d like.

For older kids we will use a ColorDome device, which will provide full field of vision stimulation. With this device, your child will lean toward the dome, and we will provide flashes with lights as described above.

The waveform resulting from the ERG includes both a-waves and b-waves. The waveform can show how well certain parts of the retina are working.