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Biomedical subjects

E Zrenner

Publications and source records attributed to E Zrenner.

At least 217 records · Page 12Linked to original sources
PubMed1987

Functional and morphological variations of fundus flavimaculatus.

In order to investigate functional differences between fundus flavimaculatus and ophthalmoscopically similar diseases, we performed testing of spectral sensitivity, transient tritanopia, visual fields, fluorescein angiography, color vision, electrophysiological parameters, dark adaptation, cone flicker threshold during dark adaptation, and a thorough clinical investigation in five patients. Four had characteristic fundus flavimaculatus, while one patient turned out to have an atypical form. All five patients showed similar results in clinical investigations, electrophysiological data, and visual field tests. However psychophysical tests showed a number of differences in the single atypical patient. Although his ophthalmoscopic picture was not entirely typical of fundus flavimaculatus, only his psychophysical data could identify the patient as functionally distinct from the other four.

Adolescent↗
PubMed1987

The effect of fluphenazine on rod-mediated retinal responses.

The effect of various concentrations of the dopamine antagonist fluphenazine on ocular field potentials, recorded under scotopic conditions from isolated, arterially perfused cat eyes, was studied. Responses from outer (isolated PIII-component of the electroretinogram, ERG), middle (b-wave), and inner (optic nerve response, ONR) retinal layers were separated. Neither the fast or slow PIII-amplitude nor the temporal characteristics of the response were influenced by any of the drug concentrations tested. In contrast, fluphenazine reversibly increased the rod b-wave amplitude over a large range of concentrations. Only very high drug concentrations led to an irreversible loss of the b-wave. In the ONR the initial transient on-response increased during drug injection, whereas the sustained on-response and off-response decreased. In summary, the dopamine antagonist fluphenazine affects mainly the signal processing of the rod pathway in the inner retinal layers, while responses from outer retinal layers are not influenced. On- and off-responses of the ONR are affected differently.

Animals↗
PubMed1987

The variable interdependence of amplitude and implicit-time in PIII, b-wave and optic-nerve responses of the cat.

Amplitude and implicit-times of responses representing different retinal layers (PIII, b-wave and optic-nerve response) were measured in electrophysiological recordings from isolated, arterially perfused cat eyes. The amplitude of these potentials was found to saturate at lower stimulus irradiances than the implicit-time in dark-adapted eyes. Light adaptation had a strong effect on the amplitudes, whereas the implicit-times were altered only slightly. Similar results were obtained in double-flash experiments. The injection of phosphodiesterase inhibiting drugs had different effects on amplitude, latency and implicit-time.

Action Potentials↗
PubMed1987

Rod-cone interaction in patients with fundus flavimaculatus.

Dark adaptation and the rise of cone flicker threshold (25 Hz) during dark adaptation were measured psychophysically in three patients with fundus flavimaculatus. The dark adaptation curve showed a delayed rod-cone break but a normal final rod threshold in all these patients. However, the rise of cone flicker threshold during dark adaptation was not delayed and also reached a normal final value. This indicates that the delay in rod dark adaptation does not influence the rise of cone flicker threshold during dark adaptation. This finding contrasts with current concepts that the rise of the cone flicker threshold reflects an increasing inhibitory influence of dark adapting rods.

Adolescent↗
PubMed1987

Double-flash responses in different retinal layers.

Stimulating the isolated arterially perfused cat eye with two consecutive flashes (double flashes) we have studied the reduction of the 2nd response recorded from outer (isolated PIII component of the ERG), middle (b-wave) and inner (optic nerve response, ONR) retinal layers. The spectral sensitivity of the mechanism that reduces the amplitude of the 2nd response, determined by a constant threshold of 20% amplitude reduction of the b-wave, could be matched by a 500 nm pigment absorption function. For a given stimulus irradiance the response reduction was largest in the b-wave and smaller in the PIII and ONR. The injection of the dopamine antagonist fluphenazine, which presumably does not influence rod receptor function, changes the ratio between the two b-wave double-flash responses. These data indicate that the reduction of the 2nd response is produced by a rod driven mechanism that has a receptoral as well as a postreceptoral component. The ONR data indicate that mechanisms in the inner retina counteract the amplitude reduction of the 2nd flash, thereby stabilizing the retinal output.

Animals↗
PubMed1986

Effects of ethyl alcohol on the electrooculogram and color vision.

Color vision tests and electrooculography (EOG) were performed in 6 male and 2 female healthy young trichromatic volunteers between 60 and 130 min after finishing consumption of ethyl alcohol leading to blood levels of approximately 0.07% to 0.16%. The average number of errors in the desaturated Panel D-15 arrangement test rose from 0.86 to 2.0; the average error score in the Farnsworth-Munsell 100-Hue test rose from 26 to 79. The axis of errors in both tests was clearly tritanopic and tetartanopic, pointing to a specific effect of ethyl alcohol on the function of blue-sensitive cones and/or their interaction with longer wavelength-sensitive cones. Ethyl alcohol decreased the size of the light-peak, apparently in a dose-dependent fashion, in each of the 16 eyes by values between 3% and 79%. The effect of alcohol on the EOG light peak was stronger between 30 and 95 min (23% decrease in average) than between 95 and 130 min (14% decrease) after the finish of alcohol administration.

Color Perception↗
PubMed1986

Cone function and cone interaction in hereditary degenerations of the central retina.

Spectral sensitivity functions and the transient decrease of sensitivity to short wavelengths after the offset of yellow light (transient tritanopia) were measured by increment threshold techniques in patients suffering from hereditary macular degenerations. Color vision defects were determined by arrangement tests and the anomaloscope. Central areolar choroidal dystrophy was found to produce a mild protan defect and to reduce foveal spectral sensitivity throughout the visible spectrum by a factor of 100; it also abolishes transient tritanopia. Electroretinogram (ERG) was normal, electrooculogram (EOG) subnormal. Stargardt's disease, despite numerous fluorescent macular spots, does not abolish transient tritanopia nor does it reduce spectral sensitivity, although scotopic matches were performed on the Nagel anomaloscope. Only in severe, advanced cases was transient tritanopia reduced and spectral sensitivity found to follow the absorption spectrum of rods. Routine ERGs and EOGs were normal. Vitelliform macular degeneration, despite the ophthalmoscopically pronounced dystrophic macula, produced only very small changes in spectral sensitivity and transient tritanopia, although a widened matching range on the Nagel anomaloscope and electrophysiological abnormalities were found. Apparently damage of the retinal circuit which connects long and short wavelength-sensitive cones, caused by hereditary conditions, is different from that caused by retinotoxic drugs.

Adult↗
PubMed1986

Characteristics of rod driven off-responses in cat ganglion cells.

The off-response of dark adapted cat ganglion cells shows a tripartite response-intensity function in the optic nerve response (ONR) as well as in extracellular recordings of single cells. While responses increase when stimuli of low or high intensities are increased, the rod driven off-response shows a strong decrease (dip) for intermediate intensities before the cone part of the function starts to rise. In contrast, on-responses increase monotonically or stay at a maximum. The dip in the response-intensity function of the off-response has a constant shape with test lights of increasing as well as of decreasing irradiance. The action spectrum of the descending part of the function peaks at 500 nm, indicating that a rod driven mechanism is responsible for the response reduction reflected by the dip. Changing the stimulus diameter from 24 deg to a 1 deg test field centred on a ganglion cell's receptive field has minimal effect on the response reduction. This points to a temporal rather than a spatial mechanism being responsible for the dip.

Action Potentials↗
PubMed1986

Differences between electroretinograms of cat and primate.

We compared the electroretinogram (ERG) evoked by pattern and uniform field stimulation using steady-state analysis in cat, monkey, and human. Evidence is provided that the pattern-evoked ERG is different in cat and primate. In primate it exhibits a resonance at 8 Hz, a spatial band-pass characteristic, contrast linearity, and no scotopic component. None of these properties are seen in the response to 8-Hz modulation in cat. The ERG evoked by a sinusoidally modulated uniform field of light is composed of a fundamental and a second harmonic component. Although the properties of the fundamental response are similar in cat and primate, the second harmonic response exhibits important differences in its temporal response and luminance dependence. The correspondence between the properties of the pattern-evoked ERG and those of the second harmonic component of the uniform field stimulus in primates suggests a common generator that is different from that of the fundamental response to uniform field stimulation. These differences in the properties of the pattern ERG in cat and primate may suggest either a different generator in cat or one with substantially different properties. This should be taken into account in animal models for the generators of the human pattern ERG response.

Animals↗