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S. Viswanathan, L. J. Frishman, A. W. Van Alstine, X. Lou, W. H. Swanson; Multifocal Photopic Negative Responses (mfPhNR) of Macaques and Humans. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4758.
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© ARVO (1962-2015); The Authors (2016-present)
Full-field ERGs contain PhNRs, following the b-wave that originate from retinal ganglion cell activity. The purpose of this study was to determine whether PhNRs can be recorded from multiple retinal locations simultaneously using the VERIS system.
mfERGs (0.1-300Hz) were recorded from anesthetized macaques before and after intravitreal injection of tetrodotoxin (TTX, 1.2-2.1 vitreal µM conc). Stimuli consisted of 7 or 19 unstretched hexagon arrays with hexagons subtending 12 and 7 deg. Presentations consisted of 30 frames per m-step with M sequence exponent of 9 and 10 for the 7 and 19 hexagon arrays. The flash strength ranged from 0.7-2.9 cd-s /m2. mfERGs were also recorded from 61 control human subjects (22-79 yrs) on two occasions using a 7 hexagon array as above with flash strength of 9.9 cd-s/m2.
mfERGs of macaques contained a slow negative potential, mfPhNR, after the b-wave with maximum trough amplitude ~75 ms. Amplitude reduced with increasing retinal eccentricity and was smallest for the hexagon with the optic disc. Similar to previous findings in the full-field ERG, TTX removed the mfPhNR and revealed a prominent i-wave. Both i and b waves were slightly delayed with stronger stimulation. mfPhNRs similar to those seen in monkeys were present in the mfERG of humans. mfPhNR timing and amplitude did not significantly correlated with age. Bland-Altman plots for test-retest variability indicated that mean differences in amplitudes and times were not significantly different from zero; the coefficient of variation (CV) of mfPhNR timing and amplitude for the central hexagon was 5.5% and 3.2% respectively. For remaining hexagons, the CV of timing and amplitude were 6.4%-10.1% and 10.3%-14.1% respectively and variability was maximal in the inferotemporal field. Further, the absolute values of the test-retest difference in timing and amplitude were not significantly correlated with mean values of timing and amplitude or with age at any test location (r2≤5%, p≥0.09).
The slow sequence mfERG contains a component similar to the PhNR of the full-field ERG that may provide an objective strategy for quick assessment of multifocal retinal ganglion cell function.
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