Multifocal ERG is a technique for assessing the local ERG from different regions of the posterior retina. It can provide detailed information of local activity of the cone system, so it is valuable in diagnosing many cases of maculopathies. Multifocal VEP offers the possibility of recording responses that originate in multiple small areas of the cortex. It is useful in early detection of glaucoma before field defects are apparent, but it will not replace automated perimetry.