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Exploring new strategies to record and analyse clinical electroretinograms
Author(s) -
LACHAPELLE P,
GAUVIN M,
LAPORTE S,
LINA JM,
LITTLE JM,
RACINE J,
DORFMAN A
Publication year - 2010
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2010.4122.x
Subject(s) - photopic vision , erg , wavelet , physics , mathematics , maxima , nuclear magnetic resonance , optics , astrophysics , artificial intelligence , computer science , retina , art , performance art , art history
Purpose Investigate if the combination of time‐frequency domain analysis and ERG dipole rotation reveals hidden features of the normal ERG that could be instrumental in the interpretation of nearly extinguished ERG responses. Methods Analyses were conducted on photopic ERGs (Photopic Hills: PH) obtained from normal subjects (n=75) and patients (n=65) affected with various retinopathies. A Discrete Wavelet Transform (DWT) was done on each ERGs and key descriptors (Holder exponent and wavelet coefficient maxima) were calculated. Dipole rotation was obtained by combining 11 gaze positions (0, 8, 16, 24, 32 and 40 degrees nasal or temporal to center) with 4 electrode locations [corneal (CE), lower lid (LL), external (EC) and internal canthi (IC)]. Results The Holder exponent follows a parabola, while some of the local wavelet maxima seem to follow a PH‐like like distribution (b‐wave and OPs) or a logistic growth function (a‐wave). In still recordable pathological ERGs, the wavelet maxima matched that found in normal ERGs evoked at low stimulus intensities while in nearly extinguished ERGs (<10% of normal) the wavelet coefficients were significantly lower. Irrespective of the direction of gaze, there was little variation in DTL ERGs. EC ERGs were the only ones to reverse in polarity (seen 5 degrees nasal to fixation in nasal to temporal shift). Conclusion The parameters obtained with the DWT offers useful and reproducible tools to help identify subtle features of residual ERGs and therefore should allow for a more accurate quantification of low‐voltage ERGs responses. Finally, our results suggest that varying the gaze and electrode positions would represent a valuable addition to the recording of clinical ERGs. Funded by NSERC.