Changes in the s-wave of multifocal electroretinograms in eyes with primary open-angle glaucoma.

Abstract

To determine whether the s-wave is present in the multifocal electroretinogram (mfERG) and whether it is altered in eyes with primary open-angle glaucoma (POAG). A Visual Evoked Response Imaging System was used to record mfERGs from 15 eyes of 15 normal adults, as control eyes, and from 15 eyes of 15 patients with POAG. The stimulus consisted of 37 hexagonal stimulating elements with luminances of 200 cd/m(2) (white), 66.6 cd/m(2) (gray), and 4 cd/m(2) (black). The white or black element was presented at five different base periods (bpds) from 13.3 to 213.3 ms according to a binary m-sequence. In the intervals between the white and black (or white) elements, gray elements were inserted at 75 Hz. The changes in the amplitude and implicit time of the s-wave of the all-trace waveform of the first-order kernel of the mfERG were compared with the mean deviation (MD) of retinal sensitivity in the whole visual field measured with a Humphrey Field Analyzer. The s-wave was present as a positive wavelet on the descending limb of the first-order kernel response of the mfERGs of all eyes with POAG. The s-wave amplitude increased with prolongation of the bpd, as occurs in normal eyes. The mean amplitudes of the s-waves at bpds of 53.3 and 106.7 ms were significantly smaller in the eyes with POAG than in the control eyes. The correlation between the s-wave amplitude and the severity of disturbance in the entire visual field indicated by the MD was not significant in eyes with POAG. The characteristics of the s-wave in glaucomatous eyes were the same as those in the control eyes, but the amplitude of the s-waves in POAG eyes was significantly lower than that in the control eyes. This suggests that ganglion cells may be involved in the development of the s-wave. When comparing the s-wave with static perimetry, more local responses of the s-wave and more local retinal sensitivity in the static perimetry will be appropriate.