MULTIFOCAL ERG

• Multifocal ERG was introduced by Sutter in the early 1990’s to stimulate multiple areas of retina simultaneously and detect each response independently.
• The test constructs a topographic ERG map of fine resolution.
• A stimulus matrix of 103 hexagonal elements are displayed on a monitor.
• The hexagons are scaled with eccentricity to elicit equal signal at all locations. Each hexagon is then alternated between black and white in a random sequence at 75 Hz.
• A bipolar contact lens is used to record the signal.
• The amplitude of each local response is estimated as a dot product between the normalized response template and each local response.
• ERG topographies can then be constructed to visualize the retinal response density.
• The recordings are presented as a negative deflection followed by a positive deflection similar to conventional a- and b-waves.
• Therefore, it can detect spatial extent of retinal dysfunction.