[The effect of the pupil as aperture and field stop on the various components of the human electroretinogram (author's transl)]. / Die Wirkung der Pupille als Apertur- und Bildfeldblende auf die verschiedenen Komponenten des menschlichen Elektroretinogramms.

The electroretinogram (ERG) was recorded in 10 normal subjects under scotopic and photopic conditions with the pupil of one eye constricted and that of the other eye dilated. The human iris, being displaced from the nodal point of the eye, acts not only as an aperture, regulating the retinal illumination, but also as a field stop, limiting the visual angle, especially for large object fields, as in Ganzfeld illumination. This double effect of a constricted pupil clearly influences the Ganzfeld ERG, not only shifting the intensity response functions to higher luminances but also diminishing the maximal responses. Control experiments with smaller test fields, which are less affected by the pupillary field-stop properties, reveal no diminution of the scotopic b-wave amplitudes. Implicit time functions, being nearly independent of the number of receptors stimulated, can be matched by taking into account the pupillary diameter and calculating the actual retinal illumination (Troland). Amplitudes, being highly affected by a decrease of responding neurons due to the angle-limiting field-stop character of the pupil, cannot be matched with regard to the pupillary diameter. This effect is most noticeable in Ganzfeld illumination for the scotopic b-wave, generated mainly by neurons of the peripheral retina, and has less effect on the photopic responses that are generated more centrally.

[Chromatic adaptation produces opposite effects on the on and off responses of the photopic electroretinogram (author's transl)]. / Gegensätzliche Wirkungen farbiger Adaptation auf den on- und off-Effekt im photopischen Elektroretinogramm.

The electrical response of the light adapted human eye to onset (a-wave) and offset (d1-wave of the positive off-effect) of monochromatic test stimuli between 448 and 654 nm (Ganzfeld stimulation, duration of test flash 0.3 s) was recorded by means of the electroretinogram in 10 normal observers during steady illumination of various wavelengths of 2.2 log Troland. During exposure to white light the spectral sensitivity of the a-wave and off-effect as determined by a criterion amplitude of 25 micronV were similar, the sensitivity of the off-effect being 0.4 log units lower as compared to the a-wave. Blue adaptation (467 nm) decreased the sensitivity of the a-wave and increased the sensitivity of the off-effect within the short wavelengths region of the spectrum. Red adaptation (630 nm) decreased the sensitivity of the a-wave and increased the sensitivity of the off-effect within longer wavelengths. Green adaptation (530 nm) produced only a small decrease of sensitivity of the a-wave for green test light, the sensitivity of the off-effect remained constant. The opposite changes of the a-wave and off-effect during chromatic adaptation demonstrate different participation of these components in the generation of color mechanisms in the human retina.

[Electro-ophthalmological observations on the course of unilateral tapetoretinal degenerations (author's transl)]. / Elektro-ophthalmologische Beobachtungen zum Verlauf einseitiger tapetoretinaler Dystrophie

A 32-year-old female patient suffering from a unilateral tapetoretinal degeneration for at least 7 years was investigated. The affected eye exhibits a typical fundus, concentric reduction of visual field, and a monophasic course of dark adaptation. The electroretinogram of the affected eye is extinguished; the electrooculogram does not show a light peak. The visual evoked cortical potential of both eyes shows a normal amplitude-stimulus intensity function. However, the first negative deflection exhibits a small difference of implicit time between the normal and affected eye. The normal eye does not show any pathological alteration.