Adaptation of the Steady-state PERG in Early Glaucoma

Abstract

Purpose Previous studies have shown that the onset of high-contrast, fast reversing patterned stimuli induces rapid blood flow increase in retinal vessels in association with slow changes of the steady-state PERG signal. We tested the hypothesis that adaptive PERG changes of normal controls (NC) differed from those of glaucoma suspects (GS) and patients with early manifest glaucoma (EMG). Methods Subjects were 42 GS (SAP MD −0.89 ±1.8 dB), 22 EMG (MD −2.12 ±2.4 dB) with visual acuity of ≥20/20 and 16 age-matched NC from a previous study. The PERG signal was sampled every ~15 s over 4 minutes in response to gratings (1.6 cyc/deg, 100% contrast) reversing 16.28 times/s. Amplitude/phase values of successive PERG samples were fitted with a non-parametric LOWESS smoothing function to retrieve the initial and final values and calculate their difference (delta) and the residual standard deviation around the fitted function (SDr). The magnitude of PERG adaptive change compared to random variability was calculated as log10 of percentage coefficient of variation CoV=100*SDr ÷ |delta|. Grand-average PERGs were also obtained by averaging all samples of the same series. Results The grand-average PERG amplitude (ANOVA, p=0.02), but not phase (ANOVA, p=0.63), decreased with increasing severity of disease. Adaptive changes (log10 (CoV) of PERG amplitude were not significantly associated with disease severity (ANOVA, p=0.27), but adaptive changes (log10 (CoV) of PERG phase were (ANOVA, p=0.037; linear trend, p=0.011). Conclusions The steady-state PERG signal displayed slow adaptive changes over time that could be isolated from random variability. PERG adaptive changes differed from those of grand-average PERGs (corresponding the standard steady-state PERG), thus representing a new source of biological information about retinal ganglion cell function that may have potential in the study of glaucoma and optic nerve diseases.

Next Generation PERG Method: Expanding the Response Dynamic Range and Capturing Response Adaptation

“…11 PERG adaptation provides specific physiological information on RGC function, 11,12 as it is selectively altered in diseases such as glaucoma 31 and optic neuritis. 21 To explore the response dynamic range and intrinsic variability over a wide range of conditions relevant to clinical application, we investigated the PERGx method in different groups of subjects including younger normal controls, older normal controls, open-angle glaucoma patients with modest visual field defects, and NAION patients with severe visual field defects.…”

Steady‐state pattern electroretinogram and short‐duration transient visual evoked potentials in glaucomatous and healthy eyes

“…Phase consistency describes the SD of these measurements. A low phase consistency indicates a failure of the RGCs to adapt to the large energy demand of an ss‐PERG stimulus, leading to different phases as testing time goes on . This difference in phase consistency is demonstrated in Figures c,d.…”

“…The PERG test depends on the integrity of the retinal ganglion cells, and thus, parameters may be altered even before VF defects appear in patients with glaucoma. Previous studies have found abnormal PERG values in patients with glaucoma suspect and ocular hypertension without optic nerve or VF changes . The PERG test represents a well‐established surrogate measure of the function of retinal ganglion cells in glaucoma with a good repeatability .…”

“…Previous studies have found abnormal PERG values in patients with glaucoma suspect and ocular hypertension without optic nerve or VF changes. 7,[10][11][12][13][14][15][16][17][18] The PERG test represents a well-established surrogate measure of the function of retinal ganglion cells in glaucoma with a good repeatability. 11 A new testing platform for steady-state PERG (ss-PERG; Diopsys Inc., Pine Brook, NJ, USA) allows for rapid administration of the ss-PERG testing sequence and can be completed within a few minutes in an office-based setting.…”

Relationship Between Transient and Steady-State Pattern Electroretinograms: Theoretical and Experimental Assessment

“…15,16,19 This may be due to the increased frequency of stimulus presentation, which results in a higher level of neural activity and, thus, increased metabolic stress. 31,32 Conventional tr PERG tr recordings show that P50 and N95 amplitudes are similarly affected in glaucoma patients, but the amplitude of the PERG SS is much more affected. 16 The overlap generation mechanism developed in this study explains this observation quite easily since P50 and N95 amplitudes contribute to the overall SS amplitude, and each tr peak reduction would result in even greater reduction in the overall SS amplitude.…”