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Multifocal Oscillatory Potentials in the ‘Two Global Flash’ mfERG in High and Normal Tension Primary Open-Angle Glaucoma

Anja M. Palmowski-Wolfe, Margarita G. Todorova and Selim Orgül

Purpose: In a previous study using the 2 flash mfERG, 90% of normal tension glaucoma (NTG) patients and 85% of high tension primary open angle (POAG) patients could be correctly classified as abnormal while 80% of the control subjects were correctly classified as normal. The purpose of this study was to analyse whether glaucomatous changes contribute to alterations of multifocal oscillatory potentials.   Methods: MfERGs were recorded from 20 NTG and 20 POAG patients and compared to those of 20 controls. The mfERG array consisted of 103 hexagons. Each m-sequence step started with a focal flash that could be either dark or light (m-sequence: 2^13, Lmax: 200cd/m2, Lmin: 1cd/m2), followed by two global flashes (Lmax: 200cd/m2) at an interval of ∼26ms. Signals were recorded with a bandpass filter at 10-300Hz. Oscillatory potentials were obtained through offline bandpass filtering at 100-300 Hz (VERIS 5.1). Focal scalar products (SP) were calculated for the response to the focal flash, the direct component at 10-40 ms (DC) and the following two components induced by the effects of the preceding focal flash on the response to the global flashes at 40-70ms (IC-1) and at 70-100 ms (IC-2). For each epoch, eight small group averages were analyzed.   Results: Overall, OPs had a larger SP in control subjects than in glaucoma subjects. In both, the response to the direct component, DC, and in the second induced response, IC2, OPs differed significantly between the control group and the glaucoma patients (repeat measure ANOVA).   Conclusion: Small areas of impaired mfOPs can be detected in both NTG and POAG in the 2 global flash multifocal OP.