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S.G. Coupland, D. Wu; International Multicenter Normative ERG Database Using the ISCEV Standard . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1669.
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© ARVO (1962-2015); The Authors (2016-present)
International Society for Clinical Electrophysiology of Vision (ISCEV) recommended a basic standardized ERG protocol so that certain ERG responses could be recorded comparably throughout the world. Cooperative multi–center collaboration at normative ERG data collection has proven largely unsuccessful due to inherent instability of the light source, the xenon flash tube. Recently, an optoelectronic electrodiagnostic system using light–emitting diode flash stimulation has become commercially available, with greater precision of luminance control. We describe an international study of the normal ERG using the same ERG protocol conducted at two centers in Peoples Republic of China and in Canada.
150 eyes from 75 normal Chinese patients aged 20–70 years (mean=38 years) and 125 eyes from 125 normal Canadian patients aged 18–79 years (mean age =39 years) were studied. Fullfield flash ERGs were recorded according to the ISCEV standard  using DTL microconductive thread electrodes. Stimulus presentation was produced by an optoelectronic LED stimulator system.
Using multivariate ANOVA there were no significant differences between the Chinese and Canadian groups on peak implicit time of a–wave and b–wave in the isolated Rod response, the Scotopic Maximum ERG, the Photopic (cone) ERG or the 30 Hz flicker. There were significant amplitude differences between Chinese and Canadian groups on the b–wave amplitude of the isolated Rod Response (p<0.03), the Scotopic Maximum ERG (p<0.001), the Photopic (cone) ERG (p<0.001) and the 30 Hz flicker trough–to–peak amplitude (p<0.0001). In all these cases the mean b–wave amplitude of the Chinese group was significantly lower than the Canadian group.
We propose that the observed b–wave amplitude differences observed are due to increased axial length in Chinese eyes as evidenced by increased mean (myopic) refractive error. These findings are consistent with recent studies by Westall et al. using the ISCEV standard who demonstrated decreased b–wave amplitudes with no change in b–wave peak latency in eyes with mild, moderate and high myopia. In conclusion, the use of multicenter normative ERG data collection has revealed striking similarities and consistent differences in electroretinal function of different populations. Marmor, M. and Zrenner, E. Standard for clinical electroretinography (1994 Update). Doc. Ophthalmol. 1995, 89; 199–210. . Westall, CA et al. Values of electroretinogram responses according to axial length. Doc. Ophthalmol. 2001, 102; 115–130.
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