Multifocal visual evoked potential is dependent on electrode position.

PURPOSE: To investigate whether the multifocal visual evoked potential (mVEP) is dependent on the electrode position, and to confirm the reproducibility of the mVEP. METHODS: The mVEPs were recorded using the Veris III system with two different bipolar electrode settings. In Position 1, electrodes were placed at equal distances in vertical alignment 2 cm above and below the inion. In Position 2, the electrodes were placed in horizontal alignment at equal distances 2 cm to the left and right of the inion. Dartboard pattern stimulation was conducted. The mVEPs were repeatedly recorded from 4 volunteers, and mainly the second-order kernel response components were analyzed. RESULTS: Although the reproducibility of mVEP was good in both Position 1 and Position 2, each waveform of the mVEP was drastically different between the two positions. This difference in the waveforms was clearly shown in the center and at the horizontal meridian. We also investigated the first-order kernel response components of the mVEPs. Several traces of the first-order kernel response components did not reveal flat traces. This point is also worthy of consideration. CONCLUSION: Responses from mVEPs are clearly dependent on the electrode position.

Multifocal electroretinograms in early primary open-angle glaucoma.

PURPOSE: To determine the utility of multifocal electroretinograms (mfERGs) in patients with early primary open-angle glaucoma (POAG) with unilateral visual field abnormalities. METHODS: mfERGs were recorded from 24 eyes of 12 cases of early POAG (stage I for 1 eye and stage II for the other eye on the Kosaki scale). The implicit times and amplitudes of the second-order kernel summed for the whole visual field, for the superior and inferior hemi-fields, and for quadrantic fields of the stage I and stage II eyes were compared. RESULTS: Neither the first- nor the second-order kernels of the mfERGs showed any changes reflecting glaucomatous visual field abnormalities. The implicit times and amplitudes of the second-order kernel summed for the whole visual field, the superior and inferior hemi-visual fields, and quadrantic visual fields of the stage I and stage II eyes were also not significantly different. CONCLUSIONS: We conclude that because the second-order kernel of the mfERG does not correlate with the visual field abnormality in early POAG, the second-order kernel of the mfERG that can be recorded at present is highly unlikely to reflect the function of the ganglion cells in the inner retinal layers.