A SLOW NEGATIVE POTENTIAL IN THE DC ELECTRORETINOGRAM OF PATIENTS WITH CONGENITAL STATIONARY NIGHT BLINDNESS

1. Patients with congenital stationary night blindness (CSNB) of the S chubert-Bornschein type show a prominent a -wave and no or a minimal b -wave, i.e. a negative electroretinogram (ERG). The disease is conside red to be caused by a transmission defect. 2. Five consecutive CSNB pa tients of this type were studied using a d.c. ERG technique to analyse the slow potentials following the b-wave. Furthermore, 30 Hz cone fli cker ERG, electrooculography (EOG) and adaptometry were performed. 3. All patients showed a negative ERG with a normal or prominent a-wave a nd only a minimal b-wave. Following the fast potentials, a slow and pr ominent negative potential was seen, replacing the positive c-wave. Du ring light stimulation (1 s), it reached a mean amplitude of about 250 -300 muV. Thereafter, it stayed at a slightly less negative level duri ng the remaining part of the 5 s recording. 4. Adaptometry showed lack of rod function. EOG and flicker ERG were normal. 5. The slow negativ e potential may reflect the combined effects of an impaired b-wave (a reduction of the positive PII) and an impaired retinal pigment epithel ial (RPE) function (a reduction of the positive PI), allowing the nega tive fast and slow PIII, representing the photoreceptors and the Mulle r cells, respectively, to dominate the response. Hyperactivity of the Muller cells cannot be excluded, however.