A Practical Introduction to Wavelet Analysis in Electroretinography

To provide a conceptual understanding of the continuous and discrete wavelet transforms (CWT, DWT) for clinical electroretinography (ERG) analysis, and how these methods uncover time-frequency features that complement traditional time-domain analysis. A technical overview without the use of mathematical formula describing the basics of CWT and DWT and implementation considerations. We also review an example of four standard ISCEV ERG recordings from a healthy male (between 30-34 years of age) and a male (between 15-19 years of age) with complete congenital stationary night blindness (CSNB). Wavelet analysis uncovered time-frequency signatures absent in raw traces. In light-adapted flicker, the normal ERG showed a ∼30 Hz response with harmonics up to 90 Hz, whereas CSNB was largely attenuated. For LA 3 and dark-adapted flashes, normal CWTs concentrated energy < 100 Hz between 0.04-0.08 s, while CSNB demonstrated lowered or almost absent energy profiles in comparison. DWT indices exhibited a similar pattern, with normal recordings demonstrating high energy responses early in the 7, 15, and 29 Hz frequency bands, while CSNB registered markedly lower values. CWT and DWT provide complementary and objective insight into ERG responses. Open-source MATLAB toolkit and step-by-step tutorial provided herein lower technical barriers and enable use by the broader community.