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Quantifying end‐stage electrophysiological function in progressive retinal degenerative disorders (PRDD)
Author(s) -
LACHAPELLE P,
GAUVIN M,
TRANG N,
LINA JM,
RACINE J
Publication year - 2011
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.1755-3768.2011.4322.x
Subject(s) - erg , photopic vision , electroretinography , retinitis pigmentosa , ophthalmology , amplitude , electrophysiology , residual , physics , scotopic vision , medicine , retinal , nuclear magnetic resonance , optics , mathematics , algorithm
Purpose PRDD, such as Retinitis Pigmentosa, are accompanied with a gradual reduction of ERG signal to non‐measurable amplitudes. We compared alternative means of quantifying normal and pathological ERGs. Methods Photopic ERGs (DTL electrode, background 30 cd.m‐2; flash stimuli: ‐2.62 to 0.64 log cd.sec.m‐2 in 17 steps of ~ ‐0.2 log‐unit) were recorded from 85 normal subjects and 55 patients with PRDD. In a subset of 6 normal subjects, focal ERGs (fERGs) were obtained with the use of a eye patch to restrict the stimulus centrally and at 20o or 40o nasally. ERG descriptors, obtained with Direct Wavelet Transform D(WT) of the ERGs, were compared to the traditional amplitude measurements. Results In normal, the ERG amplitude gradually decreased from 131.42±31.27µV (Vmax) to 0.71±0.12 µV (dimmest flash used) in two distinct pseudo‐asymptotical steps of ‐15.2±2.0µV.s (step 1) and ‐0.42±0.1µV.s per decrement respectively (9 steps each). Pathological ERGs as well as normal focal ERGs could always be fitted to this model. Furthermore, while the traditional measurements frequently failed to quantify residual ERGs, including the normal fERGs, the DWT was always able to extract quantifiable and comparable information from the residual response, thus permitting a more favourable prognosis. Conclusion Analysis of the ERG response in the time and frequency domain (such as DWT) allows for a more precise quantification of the ERG signal especially when it reaches residual amplitudes such as that observed in end‐stage PRDD. Our results suggest that modeling ERG attenuation with the DWT improves the staging and prognosis of patients affected with severe PRDD. Supported by FFB (USA).