Visual function testing using electroretinogram (ERG) signal is used to detect abnormalities of the retina. This is accomplished by measuring, characterizing and analyzing the bio potential responses from various retinal cells formed due to a visual stimulation. The objective of this study is to improve the existing ERG signal characterization models by identifying and including a key component called i-wave in the photopic response. To validate the proposed characterization model, a signal analysis and processing algorithm based on Multi Resolution Analysis has been developed to reliably separate various underlying components of this signal. Finally, the fidelity of this separation is quantitatively and qualitatively assessed by computing the Pearson's correlation coefficient and the corresponding scatter plots between the composite and the reconstructed ERG signal.