Understanding Electroretinography (ERG) Testing for Eye Conditions

Electroretinography (ERG) is a diagnostic test used to assess the function of the retina and the visual pathway. It measures the electrical activity of the cells in the retina, specifically the photoreceptors (rods and cones) and the bipolar cells, in response to light. The test can help diagnose various eye conditions such as retinal degeneration, cone dystrophy, and other retinal disorders.

During an ERG test, electrodes are placed on the surface of the eye to record the electrical activity of the retina. The patient is usually seated in a dark room and presented with flashes of light of varying intensity and duration. The electrical signals generated by the retina in response to the light stimuli are recorded and analyzed by a computer.

There are several types of ERG tests, including:

1. Full-field ERG (ffERG): This test measures the electrical activity of the entire retina in response to a full-field flash of light.
2. Multi-flick ERG (mfERG): This test measures the electrical activity of the retina in response to multiple flashes of light at different intensities.
3. Flash ERG (fERG): This test measures the electrical activity of the retina in response to a single flash of light.
4. Rod-mediated ERG (RM-ERG): This test measures the electrical activity of the rod photoreceptors in response to a low-intensity flash of light.
5. Cone-mediated ERG (CM-ERG): This test measures the electrical activity of the cone photoreceptors in response to a high-intensity flash of light.

The results of an ERG test are interpreted by a trained ophthalmologist or electrophysiologist, who looks for abnormalities in the electrical activity of the retina that may indicate a retinal disorder or disease. The test can help diagnose conditions such as retinitis pigmentosa, age-related macular degeneration, and other inherited retinal diseases.