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Biomedical subjects

G H van Lith

Publications and source records attributed to G H van Lith.

At least 37 records · Page 2Linked to original sources
PubMed1981

Electrodiagnostics of the tilted disc syndrome.

In five patients with a tilted disc syndrome the visually evoke potentials were examined by means of pattern stimulation. It was hoped that by such an examination this syndrome could be distinguished from a chiasma syndrome, since it is known that compression of the anterior visual pathways causes delayed responses, whereas defects or atrophies generally do not. In 4 patients, however, delayed responses were found and they were not found in only one patient.

Aged↗
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

Difficulties in diagnosing Leber's optic atrophy.

The lowered vision of a patient was attributed to an acute quinidine intoxication, although his condition differed from that of another patient with an acute quinine intoxication. Later, the uncle of the first patient showed lowered vision too, possibly due to a tobacco-alcohol neuropathy. Both uncle and nephew belonged to a family, in which Leber's hereditary optic atrophy occurred.

Adult↗
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↗
PubMed1980

Interpretation of the electro-oculogram of patients taking chloroquine.

No significant differences in initial EOG were found between a group of RA patients using chloroquine, a group treated with gold and a normal group. Most probably this is due to the low dosage of chloroquine which is used nowadays. After six months, EOG values in the chloroquine group were reduced, while they were increased in the gold group. The differences were statistically significant, but most be carefully interpreted, because in the group of normal subjects the EOG was lowered as well.

Arthritis, Rheumatoid↗
PubMed1980

Pattern EPS in endocrine orbitopathy.

Since delayed pattern evoked potentials (EPs) are a sensitive symptom of demyelination or compression of the optic nerve, a group of 33 patients with endocrine orbitopathy were examined in order to see whether or not, in this disease too, damage to the optic nerve could be detected at an early stage. Below a visual acuity of 0.4, all patients had delayed responses. Most interesting was the group of patients with normal visual acuity and delayed responses. Before conclusions can be drawn this group will have to be enlarged and followed up.

Demyelinating Diseases↗
PubMed1980

The application of visually evoked cerebral potentials in ophthalmological diagnosis.

A short survey is presented of what can be done with electrophysiological techniques in ophthalmological diagnosis. It is stressed that more investigation has to be done to elucidate the discrepancies between electrophysiological and psychophysical disturbances. These discrepancies can be used for the differential diagnosis. More, though still too little, is known about differences between a disturbance of latency time and that of amplitude. It seems that latencies are more disturbed in active pathological processes like demyelination, compression of nerve fibres and oedema, whereas isolated reduction of amplitudes occurs in optic atrophies. Some optic nerve diseases are found to be combined with ERG abnormalities, such as tobacco-alcohol neuropathy and some hereditary diseases.

Cerebral Cortex↗
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↗
PubMed1977

Differential diagnostic aspects between optic neurititis and chiasm tumors.

Two patients with a pituitary tumor were first considered to have an optic neuritis from the clinical picture. The electrophysiological examination with VECPs gave results which did not offer a definite differentiation between both diseases, whereas perimetry and X-ray examination were decisive.

Adenoma, Chromophobe↗
PubMed1976

Clinical importance of the electro-oculogram with special reference to the chloroquine retinopathy.

Examination of the EOG is surely worthwhile in cases of generalized pigment alteration and in juvenile foveal dystrophies. Its value in the control of chloroquine treatment is still doubted, but the method will become better if an EOG is made before treatment is started. EOGs made during the treatment can then be compared with those made earlier. As a result, the large interindividual variation is replaced by the much smaller intraindividual variation. In a group of normals and patients, the intraindividual standard deviation appeared to be about 10% of the original value of the EOG. Using this criterion, we think the EOG to be a valuable tool in preventing chloroquine retinopathy, although it is not yet certain if static perimetry with red light is still a better method.

Arthritis, Rheumatoid↗