Electoretinography

Electroretinography, often abbreviated as ERG, is a diagnostic test used to measure the electrical activity of the retina in response to light stimulation. It is a non-invasive technique that provides objective information about the function of different cell types within the retina, including photoreceptors (rods and cones) and the bipolar and Müller cells. The procedure involves placing a contact lens electrode on the eye and a reference electrode on the forehead or other parts of the body. When the eye is exposed to controlled flashes of light or patterns, the resulting electrical signals are recorded by the electrodes.

The waveform of the ERG response can be analyzed to identify various retinal disorders. Different components of the ERG waveform, such as the 'a-wave' and 'b-wave', are attributed to specific retinal cell activities. For instance, the a-wave is primarily generated by photoreceptors, while the b-wave reflects the activity of bipolar and Müller cells. ERG is particularly useful in diagnosing inherited retinal degenerations like retinitis pigmentosa, cone-rod dystrophies, and stationary night blindness. It can also be employed to assess retinal toxicity from certain medications, evaluate vision in infants and young children who cannot cooperate with subjective visual testing, and monitor the progression of retinal diseases. Specialized ERG techniques, such as multifocal ERG (mfERG) and pattern ERG (PERG), can provide more localized information about retinal function.