Amplitude of the s-wave of multifocal electroretinograms can indicate local retinal sensitivity in glaucomatous eyes.

Purpose: To determine whether the amplitude of the s-wave on a multifocal electroretinogram (mfERG) is correlated with the degree of visual field depression in eyes with glaucoma.
Methods: Twenty patients (20 eyes) with glaucoma,ages 46 to 69 years, were studied. Twenty healthy volunteers (20 eyes) with normal intraocular pressure and with no eye diseases served as controls. The retinal sensitivities of the upper and lower visual fields of the glaucomatous eyes were determined with a Humphrey Field Analyzer. The severity of retinal sensitivity depression was rated as mild (Group A), intermediate (Group B), or severe (Group C). To record the s-wave, mfERGs were elicited by pseudorandom stimulation, with the stimulus alternating according to a binary m-sequence for base periods (bpds) of 13.3, 26.7, 53.3, 106.7, and 213.3 ms. The mfERGwaves recorded from the upper and lower visual field were summed separately.
Results: In the control group, the s-wave in the summed mfERG was observed in all visual field halves at all bpds 53.3 ms or longer. The s-wave amplitude at a bpd of 213.3 ms was significantly larger than that at a bpd of 53.3 ms ( P < 0.05). The s-wave was also present in the glaucoma patients' eyes, and the s-wave amplitude increased as the bpd increased. At bpds of 53.3, 106.7, and 213.3-ms, the mean s-wave amplitudes in Groups B and C were significantly smaller than those in the control group ( P < 0.05, 0.01, and 0.05, respectively). At bpds of 53.3 and 106.7 ms, the mean amplitude of the s-waves in Group C was significantly smaller than that in Group A ( P < 0.05). At a bpd of 106.7 ms, a significant correlation was observed between the retinal sensitivity and the s-wave amplitude ( P < 0.05).
Conclusions: The significant correlation between the retinal sensitivity and the amplitude of the swave at a bpd of 106.7 ms supports the suggestion that the s-wave originates from the retinal ganglion cells and their axons. The amplitude of the s-wave may serve as an objective indicator of the severity of retinal ganglion cell damage.