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Muneyoshi Kaneko, Shigeki Machida, Yuya Hoshi, Daijiro Kurosaka; Alteration of Photopic Negative Response of Multifocal Electroretinogram in Patients with Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5130.
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© ARVO (1962-2015); The Authors (2016-present)
We previously demonstrated that the photopic negative responses (PhNRs) in patients with glaucomatous optic neuropathy (GON) showed deterioration not only in the full-field cone electroretinograms (ERGs) but also in focal macular ERGs (Tamada et al., 2010; Mchida et al., 2011), indicating that the neural activity of retinal ganglion cells (RGCs) contributes to shaping the PhNR in both full-field and focal ERGs. The present study aimed to clarify the contribution of RGC activity to shaping the N2(corresponding to the PhNR) of the multifocal ERG (mfERG) obtained using low-frequency stimuli.
Twenty five patients with GON (34-88 years old) were included. All patients had glaucomatous scotoma as determined by static visual field testing. We lowered the stimulus frequency to 6.25 Hz. 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). The mfERG was also elicited by a quarter of an annulus placed around the macula (Temporal Superior, TS; Temporal Inferior, TI; Nasal Superior, NS; Nasal Inferior, NI). The diameter of the inner border of the annulus was 13.6° and that of the outer border was 40°.
MfERG waveforms obtained using a low-frequency stimulus mimicked those of full-field cone and focal macular ERGs, which consisted first of negative- and positive-going waves (N1 and P1) followed by a slow negative-going wave (N2: corresponding to the PhNR). There were no significant differences between the normal control and glaucomatous eyes in N1 and P1 response densities in any areas. A significant difference was found in N2 response densities and the N2/N1 response density ratios in the C and TS areas, and the N2/P1 response density ratios in the C, TS and TI areas (P<0.05). However, in other stimulus areas, including NS and NI, there were no differences for any components of the mfERG.
The present results suggest that the N2 of the mfERG obtained using low-frequency stimuli reflects RGC activity in patients with GON. In the future, the mfERG could facilitate regional assessment of RGC function in glaucoma patients.
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