Electroretinography

Electroretinography (ERG) records electrical responses generated by the retina after light stimulation. Its waveforms help assess retinal function, including activity in photoreceptors and inner retinal cells.

Electroretinogram: A recording of the retina’s electrical response to light, typically displayed as a waveform. ERG measures this waveform, whose components reveal how retinal responses change over time.
Full-field electroretinography: An ERG method that stimulates the retina broadly with flashes delivered across the visual field. It assesses generalized retinal function, especially when disease affects much of the retina.
Retina: The light-sensitive neural tissue lining the back of the eye that initiates visual processing. ERG records electrical activity from this tissue rather than from the optic nerve or visual cortex.
Visual evoked potential: An electrophysiological response recorded from the visual cortex after visual stimulation. It evaluates signal transmission to the brain, whereas ERG measures the retina’s response.
Photoreceptor: A retinal cell that converts light into electrical signals; rods and cones are the main types. Photoreceptor activity generates much of the ERG’s initial negative response.
Pattern electroretinography: An ERG method that records retinal responses to alternating patterned stimuli. It helps assess central retinal function and distinguish macular from optic nerve disorders.
Retinal circuit: The network of photoreceptors, interneurons, and ganglion cells that processes visual signals within the retina. Different parts of this circuit contribute differently to the components measured by ERG.
Optical coherence tomography: An imaging technique that produces cross-sectional views of retinal structure using reflected light. OCT shows retinal anatomy; ERG measures function, so the tests can reveal different abnormalities.
Bipolar cell: A retinal neuron that relays signals from photoreceptors to ganglion cells. Bipolar-cell activity contributes substantially to the ERG’s positive b-wave.
Retinitis pigmentosa: A group of inherited retinal disorders characterized by progressive photoreceptor degeneration and visual-field loss. ERG can detect reduced rod and cone responses and help characterize disease severity.

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