Multifocal ERG with 30 Hz flicker stimulation in glaucoma patients and normal probands

Abstract

It was the aim of the present study to investigate the value of multifocal ERG with 30 Hz flicker stimulation for glaucoma diagnosis. Multifocal ERGs with 30 Hz flicker stimulation were recorded with a mean luminance of 50 cd/m2 and a contrast of 99% from the central 60 degrees of the retina which were stimulated by 61 hexagons. From 30 patients with primary and secondary open-angle and low-tension glaucomas with reproducible visual field losses and glaucomatous optic disc atrophy and 21 normal subjects, one eye was included in the study. The first harmonic wave, the basewave and the ratio of these two parameters were ana-lysed. The responses of seven neighbouring hexagons were averaged for the intraocular comparison between areas with and without perimetric defects and for the comparison between glaucomas and normal subjects. In the glaucoma group, the ratio of the first harmonic wave and the basewave was significantly lower in an area within a perimetric defect than outside the defect (p < 0.001) when compared intraocularly. The extent of ERG changes however did not correlate with the extent of perimetric defects. Comparing the glaucoma with the normal group, the ratio of the first harmonic and the basewave was significantly lower in an area within the perimetric defect in the glaucoma group than in corresponding areas of the normal group (p = 0.002). The first harmonic and the basewave did not differ significantly. These results show that the method is not appropriate to objectively indicate visual field losses although it statistically separates glaucomas from normal subjects.