Purpose. To investigate the electrophysiological findings of a multifocal ERG in multiple evanescent white dot syndrome (MEWDS).

Methods. Multifocal electroretinograms (mf-ERG) were recorded from four patients with MEWDS. The stimulus array consisted of 61 hexagons and was presented according to a binary m-sequence. We analyzed the N1- and P1-wave amplitudes as well as P1 latencies of the first-order kernels. Local responses and concentric ring averaged responses were compared to 20 age-matched normal subjects. All patients underwent fluorescein angiography and indocyanine green angiography.

Results. In two patients, first-order kernel of N1- and P1-wave amplitudes showed supernormal results at the very beginning (day 1 to day 7) of the disease. By 2 weeks later, N1- and P1-wave amplitudes had decreased to either normal or subnormal values. The two patients who presented 2 weeks after the onset of clinical signs showed subnormal or decreased amplitudes. The P1 implicit times were within normal limits in all patients.

Conclusion. Our mf-ERG findings show different results during the course of the disease. First-order kernel amplitudes seem to reflect early disturbances of the photoreceptors in MEWDS and are therefore useful in detecting early stages and following up the disease.