Research Article Advance in ERG Analysis: From Peak Time and Amplitude to Frequency, Power, and Energy Mathieu Gauvin, 1 Jean-Marc Lina, 2,3 and Pierre Lachapelle 1 1 Department of Ophthalmology & Neurology-Neurosurgery, Montreal Children’s Hospital Research Institute, McGill University, 2300 Tupper Street, Montreal, QC, Canada H3H 1P3 2 D´ epartement de G´ enie ´ Electrique, ´ Ecole de Technologie Sup´ erieure, Montr´ eal, QC, Canada 3 Centre de Recherches Math´ ematiques, Montr´ eal, QC, Canada Correspondence should be addressed to Pierre Lachapelle; pierre.lachapelle@mcgill.ca Received 10 April 2014; Accepted 30 May 2014; Published 1 July 2014 Academic Editor: Jerzy Nawrocki Copyright © 2014 Mathieu Gauvin et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Purpose. To compare time domain (TD: peak time and amplitude) analysis of the human photopic electroretinogram (ERG) with measures obtained in the frequency domain (Fourier analysis: FA) and in the time-frequency domain (continuous (CWT) and discrete (DWT) wavelet transforms). Methods. Normal ERGs ( = 40) were analyzed using traditional peak time and amplitude measurements of the a- and b-waves in the TD and descriptors extracted from FA, CWT, and DWT. Selected descriptors were also compared in their ability to monitor the long-term consequences of disease process. Results. Each method extracted relevant information but had distinct limitations (i.e., temporal and frequency resolutions). he DWT ofered the best compromise by allowing us to extract more relevant descriptors of the ERG signal at the cost of lesser temporal and frequency resolutions. Follow- ups of disease progression were more prolonged with the DWT (max 29 years compared to 13 with TD). Conclusions. Standardized time domain analysis of retinal function should be complemented with advanced DWT descriptors of the ERG. his method should allow more sensitive/speciic quantiications of ERG responses, facilitate follow-up of disease progression, and identify diagnostically signiicant changes of ERG waveforms that are not resolved when the analysis is only limited to time domain measurements. 1. Introduction he electroretinogram (ERG) identiies the electrical signal that is generated by the retina in response to a light stimulus. It is the irst biopotential ever recorded from a human subject, namely, by Dewar in 1877 [1]. However, despite signiicant (r)evolution in the recording technologies (essentially from the string galvanometer to the digital ampliier and support- ing computer sotware) and, consequently, the signiicantly enhanced quality of the ERG signal thus obtained, analysis of the ERG remains for the most part limited to amplitude and peak time measurements of its major components, namely, the a- and b-waves. his is at least what is recommended in the ERG standard of the International Society for Clinical Electrophysiology of Vision (ISCEV) [2]. he a- and b- waves of the ERG are said to relect the activity generated by the photoreceptors and the bipolar-M¨ uller cell complex, respectively [3–5]. hese components are usually referred to as the slow waves of the ERG. Also identiied in the ERG signal are the small, high-frequency, oscillations that are oten seen riding on the ascending limb of the b-wave [6, 7]. hese components, referred to as oscillatory potentials (OPs), are most probably generated by the retinal cells of the inner retina (i.e., bipolar, amacrine, or horizontal cells) although their exact origin remains debated [8, 9]. he OPs appear to be major contributors to the shaping of the ERG waveform [10] and there is an abundant literature attesting to the clinical value of including the OPs when analyzing pathological ERGs [6, 11, 12]. Unfortunately, in order to optimize the visualization of the OPs one must modify the recording bandwidth of the ERG from a broadband (e.g., 1–1000 Hz) to a narrower band (e.g., 100–1000 Hz) that removes the low- frequency components of the ERG (i.e., a- and b-waves) and consequently selectively enhances the high-frequency components (i.e., OPs) [2]. However, when doing so one must always keep in mind the possibility of introducing artifactual Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 246096, 11 pages http://dx.doi.org/10.1155/2014/246096