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Muneyoshi Kaneko, Shigeki Machida, Yuya Hoshi, Daijiro Kurosaka; Alteration of implicit time of photopic negative response in multifocal electroretinograms for patients with glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):485.
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© ARVO (1962-2015); The Authors (2016-present)
We previously demonstrated that the N2 response densities in 5- or 7-element multifocal electroretinograms (mfERGs) obtained using low-frequency stimuli were reduced for patients with glaucomatous optic neuropathy (GON), and reflected the activities of retinal ganglion cells. The present study aimed to clarify whether the implicit time of the N1, P1 and N2 response densities in mfERGs obtained using low-frequency stimuli show any change for patients with GON.<br />
Forty five patients with GON (34-88 years old), who had glaucomatous scotoma as determined by static visual field testing, were included. The stimulus frequency was reduced to 6.25 Hz, and the low- and high-cut filters of the amplifier were set at 3 and 30 Hz, respectively, to record slow waves. The mfERG was elicited by a 13.6° circular stimulus centered on the fovea (Center, C), and also by a quarter of an annulus placed around the macula (Temporal Superior, TS; Temporal Inferior, TI; Nasal Superior, NS; Nasal Inferior, NI). The inner border of the annulus spanned an angle of 13.6°, and the outer border spanned 40°. The all-trace waveform of the first-order kernels was obtained by averaging the local retinal responses from five different retinal loci.
The mfERG waveforms obtained using the low-frequency stimulus mimicked those of full-field cone and focal macular ERGs, and consisted first of negative- and positive-going waves (N1 and P1) followed by a slow negative-going wave (N2: corresponding to the photopic negative response). A significant difference was found in the implicit time of N1 in the C area (P<0.05), that of N2 in the TS (P<0.001), TI (P<0.001), NS (P<0.01), and C (P<0.001) areas, and that of N2 in the all-trace waveform (P<0.005). However, in other stimulus areas, there were no differences in the implicit times of any components of the mfERG.<br />
The present results suggest that the implicit time of N2 in mfERGs obtained using low-frequency stimuli reflects RGC activity in patients with GON. It is therefore possible that such mfERGs could be used to detect early glaucomatous changes.<br />
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