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Biomedical subjects

M R Lessel

Publications and source records attributed to M R Lessel.

At least 19 recordsLinked to original sources
PubMed1993

The dark trough in clinical electro-oculography. Influence of preadaptation on amplitudes and latencies.

The influence of four different intensities of the preadapting light on amplitude and implicit time of the dark-induced oscillation (dark trough) of the electro-oculogram was tested in 10 healthy individuals. The amplitude of the dark trough (normalized to preadapting baseline) was found to be dependent on the intensity of the preadapting light (analysis of variance: p < 0.0001). No correlation could be proven between preadapting light intensity and the implicit time of the dark trough (p = 0.299). The confidence intervals of the implicit time of the dark trough exceeded 14 minutes in all four intensity settings. There was no significant dependence of the absolute baseline values on preadapting intensities (p = 0.236).

Adult↗
PubMed1993

Comparison of electro-oculogram recording methods.

The purpose of this study was to compare the variability of the amplitude ratios and latencies of the electro-oculogram (EOG) light peak (LP) in three different recording conditions: Arden ratio (dark trough (DT): 12 min), modified Arden ratio (DT: 15 min) and light peak/dark baseline ratio (LP/BL: 35 min of dark adaptation). Additionally, EOGs from eyes with dilated and undilated pupils were recorded. The light intensity stimulating the eyes with dilated pupils was attenuated 1 log unit. The EOG amplitude ratios displayed no significant difference between the three conditions tested. The comparison of implicit times (time from onset of light exposure to LP) revealed significantly (p < 0.001) shorter values when the recording of the LP was preceded by a dark adaptation of 35 min. The broadening of the curves in DT/LP recordings might be caused by a superposition of a residual dark oscillation on the LP. The recordings from eyes with dilated pupils--stimulated with 1 log unit lower intensity--revealed lower amplitude ratios than the recordings from eyes with undilated pupils.

Dark Adaptation↗
PubMed1993

Prostacyclins in diabetes: an electrophysiological study.

Twelve patients with juvenile (insulin-dependent, type I) diabetes were treated either with prostacyclins or placebo in a double-masked randomized study. The electroretinogram (ERG) was recorded before, 1 day and 8 months after treatment. An analysis of variance and covariance was carried out to evaluate possible treatment or time effects on the a and b waves and the oscillatory potentials of the ERG. Mean values of potentials displayed a decrease of amplitude and an increase of latency over the follow-up period in all patients. No statistically significant difference between treated and placebo groups could be proven.

Adult↗
PubMed1989

The slow electrooculogram oscillation in malignant choroidal melanoma.

Electrooculographic recordings were performed in a series of patients with malignant choroidal melanoma. The amplitudes of the light peaks were reduced in all cases compared with the recordings of the normal fellow eyes. The amount of reduction of the light peaks appeared to be dependent on localization of the tumor. The electrooculograms of eyes with tumors of the posterior pole were found to be reduced significantly. Eyes with malignant melanomas located in the peripheral fundus displayed minor reductions.

Adult↗
PubMed1989

The peak latency of the slow oscillation in EOG.

Peak latencies of the light-induced slow electrooculograph oscillations of 61 patients were analyzed. The wide range of variation of the results of the control group obtained in this study did not allow inferences relevant for the differential diagnosis of retinal diseases. Most of the data were within the limits of normal values.

Electrooculography↗
PubMed1988

The c-wave in achromats.

In congenital total color blindness direct current recordings of the electroretinogram displayed a negativity following the b-wave, not present in recordings of normal eyes. This negativity, preceding the onset of the c-wave, is probably caused by the lack of cone contribution to the positive c-wave component.

Child, Preschool↗
PubMed1986

Light induced oscillations of the standing potential in achromatopsia.

In three children with achromatopsia light-induced oscillations of the standing potential and electroretinograms (ERGs) were recorded. A low drift direct current recording system was applied to monitor the changes of the standing potential under general anesthesia. In all children the scotopic ERG components were normal. No photopic components could be observed. The fast oscillations of the standing potential were normal under scotopic and photopic conditions. The light-induced slow increase of the standing potential displayed low amplitudes and normal peak latencies. The results of our study support earlier investigations suggesting that cone-mediated mechanisms in the retina contribute a significant component to the amplitude of the light peak in the electroretinogram.

Child, Preschool↗
PubMed1986

[Localized forms of retinopathia pigmentosa].

Classification of localized forms of peripheral retinitis pigmentosa can be performed according of the pigmented areas: Unilateral RP (URP): Probably a phenocopy. It mimics typical RP clinically and electrophysiologically in one eye, sparing the fellow eye. Sector RP (SRP): Bone corpuscle-like intraretinal pigmentations a cover a fundus sector (mainly the lower half of the fundi). Corresponding field defects. Progressive paravenous retinochoroidal atrophy (PPRCA): Paravenous distribution of retinal pigmentations. Tongue-shaped field defects. Peripapillary RP (PPD): Pigmentary retinal deposits in the area surrounding the optic disc. Corresponding field defects. Electrophysiology is an important tool in the diagnosis of localized forms of retinitis pigmentosa: The amount of reduction of ERG amplitudes corresponds to the pigmented retinal area. The impaired EOGs indicate a general involvement of the retinal pigment epithelium. In contrast, acquired-e.g. postinflammatory or circulatory-processes display normal EOGs.

Chorioretinitis↗
PubMed1986

ERG and EOG in progressive paravenous retinochoroidal atrophy.

A case of paravenous retinochoroidal atrophy was followed over a period of more than 2 years. Rapid progression of the disease was reflected in the deterioration of visual acuity and fields. Electroretinographic recordings revealed reduced photopic and scotopic amplitudes according to the extent of the retinal lesions. In electrooculography virtually no slow and no fast light-induced oscillations could be recorded. These results suggest an involvement of the entire retinal pigment epithelium.

Adult↗
PubMed1986

The influence of intravitreously injected silicone oil on electrophysiological potentials of the eye.

In a prospective study the effect of silicone oil injected in the vitreous cavity was monitored electrophysiologically in six patients who were treated for retinal detachment. Electroretinograms (ERG) and electrooculograms (EOG) were recorded before, shortly after, and up to four months following the removal of the oil. An evident increase of the standing potential could be observed in all eyes after removal of the silicone oil. In some patients the ERG amplitudes increased also. No fast oscillations and virtually no slow oscillations could be recorded in the EOG. Follow-up studies did not show a significant recovery of the bioelectric activity. Intravitreal silicone oil appears to cause an insulation effect which interferes with the propagation of electrical potentials. The result of the present study do not provide information concerning possible retinotoxic effects of silicone oil.

Electrooculography↗
PubMed1983

[Modified video-pupillography: indications and 1st experiences].

Besides of infrared-reflexphotometry several videosystems are used for pupillography. The main modification of our TV-pupillography consists of the connection of the infrared-camera with a videorecorder. Thus changes of the shape of the pupil can be evaluated continuously. Therefore, indications for our variant of pupillography are especially those types of anisocoria with loss of the round shape of the pupils.

Humans↗
PubMed1982

[Modification of the swinging flashlight test].

As a simple screening method our modification of the Swinging Flashlight Test permits unilateral organic and functional visual disturbances to be differentiated in patients with clear media and normal fundi and, in addition, photographic documentation of the results. An additional advantage of the authors' method is the exclusion of possible artefacts inherited in the Swinging Flashlight Test.

Humans↗
PubMed1982

[Fast oscillation of the electro-oculogram. Amplitudes and latencies in the course of slow oscillation].

In ten normal subjects the fast and slow oscillation of the electro-oculogram were elicited simultaneously by repetitive light stimuli. A slow oscillation evoked by continuous light of lower intensity was subtracted from the combined curve by use of a computer program. No influence of the slow oscillation on amplitudes and latencies of the fast oscillation could be proven in the resulting curve.

Computers↗
PubMed1982

The fast oscillation of the electro-oculogram. Influence of stimulus intensity and adaptation time on amplitude and peak latency.

The dependence of amplitudes and peak latencies of the light-induced fast EOG oscillation was studied using rectangular light stimulation. A linear increase of the amplitude was observed in the intensity range tested (24-3,000 asb). No influence of the time of preadaptation to darkness on the amplitudes could be proven in a range of 20 s to 21 min. The peak latency was not dependent on light intensity. Prolonged peak latencies were observed following short and long periods of dark adaptation.

Adult↗