A comparison of two multifocal ERG systems

The First Order Kernel responses (FOK) from a group of 15 normal subjects a ged 21-36 yrs were recorded under clinical conditions with the multifocal E RG (MERG) systems VERIS and RETiscan using system-specific software and har dware under Various parameter settings. First, the multifocal ERG's of norm al subjects were recorded with the standard-parameters of VERIS and RETIsca n. Thereafter the VERIS system parameters were set as close as possible to the RETIscan-setup, and the recordings were repeated. The VERIS parameters changed were the luminance- and contrast-settings of the stimulus-monitor a nd m-sequence-timing. In addition, the effects of different sampling rates were also examined. The consequences of the parameter changes were analyzed by displaying the peak times of the First-Order-Kernel (P1). The parameter -combinations used for recording lead to system-specific results. By varyin g the luminance/contrast settings and/or the m-sequence-timing the results can be changed. The amplitude of the recorded results can be influenced by the luminance-settings of the stimulus-monitor, and the topography of the P 1 peak times is affected by the m-if-frame-combination of the recording sti mulus. With their standard parameters, the two systems give different measu res of the PI peak times. By adjusting the recording parameters. these diff erences can be reduced significantly. The main parameter here is the m-sequ ence-timing, although the sampling rate must also be taken into account wit h regard to the accuracy of the recording results.