Investigation of retinitis pigmentosa using the multifocal electroretinogram.

Retinitis pigmentosa (RP) patients have pathological changes in both the macula and the periphery, and are known to have abnormal electroretinograms (ERGs). The response densities measured by the multifocal electroretinogram (MERG) in the macula and pericentral retina were greatly reduced in RP. In photopic conditions, some patients had relatively better ERG responses in the macula than in the pericentral retina, and this agreed with the finding that there is usually relatively well-preserved macular function in RP. In scotopic conditions, both macula and pericentral retina gave poor responses. There was very little increase in response as stimulus luminance increased in RP. The topographical mapping of the MERG results can provide objective, localized assessment of retinal function.