P50: A foveal wavelet in the nonlinear component of multifocal electroretinogram

Purpose : To observe a foveal wavelet (P50) in the first slice of the second order kernel (K2.1) of multifocal ERG recorded with a 75 Hz base rate in healthy subjects. Methods : mfERGs with 37 or 509 stimulus elements obtained from 42 healthy subjects were analyzed. Results : With 37-element mfERGs, the P50 with a peak time around 50 ms was observed in the K2.1 only at the centermost element without exception. The 509-element mfERG revealed that the P50 was distributed only in approximately 3° radius in the center and its peak time was nearly-constant within the area. Conclusions : The waveforms of the nonlinear kernels in the fovea were much different from that obtained by full field stimulus, probably reflecting the uniqueness of the foveal retina Among them, the P50 unexceptionally identified among healthy subjects appears promising to assess the foveal function in an impaired macular. In order to utilize the P50, it would be favorable to optimize the stimulus conditions and/or a group setting of mfERG to enhance the P50.