The Diopsys® NOVA-pERG is a retinal biopotential that is evoked when a temporally phase-reversed horizontal/checkerboard grating pattern of constant total luminance is viewed. The contrast and viewing angle of the stimulus is optimized to elicit detection of dysfunction of the macula or the retinal ganglion cells selectively. The two NOVA-PERG reporting protocols are Contrast Sensitivity (CS) and Concentric Stimulus Fields (CSF). CS is optimized to detect dysfunctions of the retina that are sensitive to discrimination between different contrast levels while the CSF is optimized to localized pathologies in specific regions of the retina such as central vision and macula. Currently both protocols utilize steady-state technology.