Pattern ergs and check size: absence of spatial frequency tuning

The pattern electroretinogram (PERG), whose genesis appears to depend upon intact retinal ganglion cells, is receiving attention from clinical electrophysiologists because of its possible value as an aid in the diagnosis of optic nerve disease. Until now there have been no published studies describing the PERG in a large normal population nor has the effect of check size been systematically investigated in normals. We have investigated peak latency, amplitude and interocular amplitude ratio of the P, Q and R-waves of the PERG and their relationship to several pattern visual evoked potential (PVEP) parameters. In 35 normal subjects simultaneous PERGs and PVEPs were recorded using four different check sizes. The study of these small amplitude waveforms was facilitated by digital subtraction of eye movement artefact. The distribution of normal control data is described and a clinical terminology for the PERG components is proposed.