Biomedical subjects

S Vijfvinkel-Bruinenga

Publications and source records attributed to S Vijfvinkel-Bruinenga.

9 recordsLinked to original sources

PubMed1986

The pattern-elicited electroretinogram. I. A tool in the early detection of glaucoma?

The pattern-elicited electroretinogram (PERG) was recorded in 75 patients known with glaucoma, each one of them having a normal visual acuity, and compared with the results in normal test subjects. Although there is a great overlap between normal and glaucomatous eyes, a lower average amplitude and a delay in latency is recorded in the case of glaucoma. A correlation was sought between the PERG outcome on the one hand and different glaucomatous parameters (visual field loss, intraocular pressure, cup disc/ratio) on the other; this could only be confirmed for the cup/disc ratio. In beginning glaucoma the PERG is more often disturbed than the VECP.

Adult↗

PubMed1984

A standardized method for recording pattern-elicited electroretinograms in normal human subjects.

The pattern-elicited electroretinogram may be a useful tool for a further refinement of electro-ophthalmological diagnosis. Before being able to detect abnormalities under various pathological conditions, it is necessary to standardize the procedure and calculate the values for normal human test subjects. The routine procedure for these experiments is described and the data obtained are presented. This method appears to be reproducible and useful and is little time consuming in a diagnostic laboratory set-up.

Adult↗

PubMed1982

Pattern evoked cortical potentials and compressive lesions along the visual pathways.

It is stressed that not only demyelinating diseases, but also compressive lesions along the anterior visual pathways, may cause severely disturbed or clearly delayed occipital potentials to pattern reversal stimulation. Only tumors exerting real pressure on optic nerve fibres cause these relatively marked disturbances of the pattern responses. Such tumors are tumors of the optic nerve itself, those along the optic canal, at the base of the anterior fossa or around the chiasm, and not tumors of the orbit or those situated beyond the chiasm.

Adenoma, Chromophobe↗

PubMed1982

Normal values of the basic level of the standing potential and its light rise.

The amplitude and the light rise of the standing potential of the eye were measured in a group of 20 male and 10 female health young subjects. The basic value itself, if measured in the steady state, has a variability not far from its light rise, so it can also be applied clinically. The median base value in our group was 362 microV, with normal limits of 233 and 680 microV. If the light rise is calculated in relation to its basic level, the variability of such a ratio is lower than the variability of the light peak/dark trough ratio. The mean value of our ratio wa 2.19 with a lower limit of 1.57. Maximal normal difference between two eyes of the same subject was 122 microV for the basic value, and 0.45 for the ratio.

Adult↗

PubMed1981

ERG and VECPs in retinal detachments.

In retinal detachments the scotopic ERG is generally more disturbed than the photopic ERG; both are more disturbed than would be expected from the visible detached retina. The disturbance is characterized by a reduction of both the a-wave and the b-wave. Furthermore, the photopic responses are clearly delayed when the detachment extends over more than half of the retina, giving a typical, even pathognomonic, wave form when the detachment covers more than three quarters of the retina. Even in total detachments, such a response, though very small, can usually be obtained, as well as a VECP after strong light flashes. Most likely they are responses of the detached retina.

Electroretinography↗

PubMed1981

The standing potential of the eye in retinal detachments.

To investigate the standing potential and its light rise in retinal detachments, a group of 33 patients was examined preoperatively. The group was divided into 3 subgroups according to the extent of the detachment. Apart from practical interest, this investigation was carried out to answer the question whether contact between the pigment epithelium and the receptor layer is necessary for the generation of the standing potential. This appeared not to be the case, on the contrary the standing potential was often higher. The EOG light rise, on the other hand, was more distributed in comparison with the extent of the detachment. Various features of the EOG may be explained, if we assume an inhibitory action of the retina on the generator of the standing potential under normal conditions.

Electrooculography↗

PubMed1980

Ophthalmological examination of patients taking chloroquine.

EOGs have been routinely measured once a year in rheumatoid arthritis (RA) patients treated with chloroquine derivatives. Criterion for the advice to stop the treatment was a decrease in the EOG of more than 20% of the value obtained before treatment was started or, where this value had not been determined, a decrease in the EOG to below 1.85, i.e. the Arden criterion. Evaluating the results, it appears that in RA patients, examined once a year, the variability of the EOG is approximately 30% of the value obtained. Furthermore, instead of a lower limit for the normal value of 1.85, we found in the rheumatism group 1.6. If these new criteria were to be applied, less than 4% of the patients would be advised to stop chloroquine treatment. We wounder whether check-ups of these patients remain necessary when dosage of chloroquine or its equivalent is below 75 g per year.

Arthritis, Rheumatoid↗

PubMed1980

Two disadvantages of a television system as pattern stimulator for evoked potentials.

The use of television systems to generate patterned stimuli for the examination of EPs has disadvantages due to the frame frequency of 50Hz of television sets. Because of this, changes in the pattern last 20 msec, with the result that the variability in EP latencies is larger than in the results obtained by projector systems. Furthermore, 50 Hz noise on the recordings, transmitter through the visual system, may be seen.

Evoked Potentials↗

PubMed1979

Interference of 50 Hz electrical cortical potentials evoked by TV systems.

Application of TV systems for generating patterned stimuli for the examination of the electrical cortical potentials has disadvantages caused by the frame frequency of 50 Hz of TV sets. Apart from a larger variability in latency times of the electrical potentials as compared to the results obtained by projector systems, a 50-Hz noise on the recordings mediated through the visual system may be seen. These disadvantages can be ameliorated by increasing the frame frequency of the TV set.

Evoked Potentials↗