An Electrophysiological and Psychophysical Study of Two Forms of Congenital Night Blindness

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Abstract

Ninety-five patients suffering from congenital nyctalopia were examined electrophysiologically, and 19 of them were examined also psychophysically. They were divided in two groups according to the ERG pattern; the first as described by Schubert and Bornschein, the second by Riggs. The presence of scotopic activity was demonstrated in most cases by the ERG. Its recovery during dark adaptation ivas explained in terms of the normal ERG and shown not to be paradoxical as assumed before. The interpretation of the electrophysiological data was confirmed by psychophysical measurements. These showed the scotopic luminous efficiency to be below normal by more than 3 log units at the steady state of dark adaptation in the first group, and about one log unit below normal in the second. In both groups photopic sensitivity was also subnormal. The visual evoked response of the striate cortex was generally lengthened in latency and subnormal in amplitude. The disease appears to be caused by an abnormal neural transmission in the retina. Evidence was presented of progressive cases of congenital nyctalopia. The ERG described by Riggs is unlikely to be a precursor of that described by Schubert and Bornschein. We did not observe a relation between the type of nyctalopic ERG pattern and the hereditary mode of the disease.