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Diego Alba, Amy Michelle Huang, Shiva Roghaee, Akil Hinds, Maja Kostic, Vittorio Porciatti; Sector analysis of PERG: association with structure of Retinal Ganglion Cells and axons. Invest. Ophthalmol. Vis. Sci. 2020;61(7):769.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal Ganglion Cells (RGC) of the nasal side of the fovea, compared to those of the temporal side, are known to have higher cell density and shorter axonal distance to the optic nerve head. We investigated whether these structural differences are reflected in the PERG amplitude, latency and adaptation.
Steady-state PERGs were recorded in a group of normal subjects (n=31) using a new PERG device (Jorvec, Corp, PMID: 28553559) with a patterned-LED display (14 x 14 cm, 800 cd/m2, 1.6 cycles/deg, 15.63 reversals/s, 98% contrast). The stimulus display was divided in 4 equal triangular sectors (Inferior, I; Nasal, N; Superior, S; Temporal, T) spanning 12.5 degrees eccentricity at a viewing distance of 30 cm. Amplitude (zero-to-peak in nanoV) and phase in degrees (latency in ms) of Fourier-isolated 15.63 Hz PERG response component were assessed for each sector. Adaptation was calculated as the ratio between the amplitude at the beginning of the test (0-30 s) and the amplitude at the end of the test (100-130 s).
Results: The mean PERG amplitude was significantly different (GEE statistics, P=0.002) between sectors (I: 257 nV; N: 331 nV; S: 285 nV; T: 267 nV). Significant (P<0.05) differences were, N>T; N>I. The mean PERG latency was not significantly different (P=0.26) between sectors (I: 52.8 ms; N: 53.9 ms; S: 54.0 ms; T: 54.3 ms). The mean amplitude adaptation ratio was different between sectors (P=0.008; I: 1.0; N: 1.1; S: 1.3; T: 1.3). Significant (P<0.05) differences were, S>I; T>I. The mean Noise (28 ±12 nV) was not different between sectors (P=0.3).
The steady-state PERG displays sectorial differences in normal subjects. The naso-temporal amplitude difference (~20%) is consistent with reported differences in RGC density between corresponding sectors in human and non-human primates. The superior-inferior difference in amplitude adaptation (~30%) may mean that there are sectorial differences in the ability of RGCs to autoregulate their activity in response to metabolically challenging stimuli (PMID: 15790894). The lack of naso-temporal latency asymmetry indicates that the steady-state PERG does not reflect differences associated with different axonal distances between the stimulated sectors and the optic nerve head.
This is a 2020 ARVO Annual Meeting abstract.
Grand average PERGs recorded for different sectors in the macular region (N=31 normal subjects)
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