The ERG is a small response that is generated by the retina in response to light. The response recorded provides information about how well the photo receptors are changing light into a signal that passes to the optic nerve. Rod and cone function can be differentiated, as well as and inner and outer retinal function, by changing wavelength, intensity and duration of a flash stimuli under different states of dark and light adaptation. The recorded ERG waveform is a summation of retinal potentials from all retinal areas, which have different polarity, latency and amplitude. An ERG can also be recorded in response to an alternating checkerboard pattern (pattern ERG). This provides information about the part of the retina that images are focused on (macula). |