Die Dunkeladaptation der Achromaten

Summary

Fourteen achromats were re-examined with special attention to the course of dark adaptation. According to the degree of colour deficiency and the range of flicker fusion frequency in the ERG there were 10 cases of complete achromatopsia and 4 cases with incomplete forms. The cases with complete congenital achromatopsia presented a uniform picture: the subjects affected were not able to distinguish colours at all; the ERG showed subnormal amplitudes of a- and b-waves and a flicker fusion frequency with a maximum of 10 cps according to the lack of photopic components; the course of dark adaptation was monophasic within the normal range or near to it.

The patients with incomplete forms of achromatopsia varied in many respects: their ability to discriminate between colours was affected to varying extents; the amplitudes of a- and b-waves in the ERG were near the upper limit of normal in 3 cases and subnormal in one, and the flicker fusion frequency was between 35 and 45 cps; the threshold of dark adaptation was almost normal in one case and elevated in 3 cases.

In a 15th case, a boy now 13 years of age, the clinical symptomatology and the scotopic ERG had led to the diagnosis of an incomplete form of achromatopsia 5 years earlier. Rechecks revealed that his defective colour vision was continuing to deteriorate and that the ERG-amplitudes had decreased. Therefore this case had to be re-classified as one of progressive retinal degeneration with special involvement of the cone mechanism.

Finally the pathogenesis of congenital achromatopsia and its probable relationships to heredodegenerative retinopathies are discussed.

Zusammenfassung

Die Prüfung der Dunkeladaptation von 14 Patienten mit angeborener totaler Farbenblindheit ließ bei den 10 Fällen mit kompletter Form keinen wesentlichen Unterschied zum Kurvenverlauf der normalen Kontrollgruppe erkennen. Die Endschwellen der Dunkeladaptation der 4 Personen mit inkompletter angeborener Farbenblindheit lagen bei 3 über dem Normbereich und waren einmal etwa normal. Die Verlaufskontrolle eines weiteren Patienten, dessen Sehstörung ursprünglich in den Formenkreis der kongenitalen Achromatopsie eingereiht worden war, ergab, daß es sich bei ihm um eine progressive Degeneration des Zapfen- und Stäbchen-apparates handelt.