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Biomedical subjects

G H Van Lith

Publications and source records attributed to G H Van Lith.

9 recordsLinked to original sources
PubMed1991

Pattern electroretinography in senile macular degeneration.

The value of pattern electroretinography (PERG) for the detection and differentiation of senile macular degeneration (SMD) was assessed. A group of patients with atrophic SMD and a group with exudative SMD were compared with an age-matched reference group. Differences were only found in visual acuity and in the amplitude of the negative peak N95. No statistical differences between the atrophic and exudative groups were found. Conclusions may be drawn from these results with regard to the use of PERG in senile macular degeneration.

Aging↗
PubMed1981

Drusen of the optic disc and occipital transient pattern reversal responses.

Compression of visual nerve fibres generally markedly increases the latency times of visually evoked occipital responses. If a visual fluid defect in optic disc drusen is caused by compression of nerve fibres, delayed responses would be expected in this condition too. Examination of 23 patients (43 eyes) with optic disc drusen revealed that even the cases with serious field defects showed no marked delay in the pattern responses. As a consequence, examination of pattern responses is of no value in predicting progressive visual damage in patients with drusen. As to an understanding of the cause of the field defects, the normal pattern responses excluded direct mechanical compression on the nerve fibres by drusen. More likely they are due to a circulatory disturbance in the small vessels, which in its turn may even be caused by gentle compression by the drusen.

Adolescent↗
PubMed1978

Cortical potentials evoked by a TV pattern reversal stimulus with varying check sizes and stimulus field.

With the use of television equipment the influence of check size and stimulus field on the pattern evoked cortical potentials was investigated. Maximum responses were found with 20' and 40' checks. The major part of the responses was initiated from a ring between 1.25 degrees and 2.5 degrees eccentricity, though relatively per stimulus area the response became progressively larger the smaller the stimulus field.

Evoked Potentials↗
PubMed1978

Variation in latency times of visually evoked cortical potentials.

Latency times of visually evoked cortical potentials stimulated by reversal of a slow checkerboard pattern are highly dependent on the time needed to accomplish the reversal movement. If, owing to the method, the pattern reversal time is not kept stable, variability of the latency times is unnecessarily high for clinical purposes. This may be the case when television equipment is used.

Evoked Potentials↗
PubMed1977

Electro-ophthalmology and side-effects of drugs.

Diagnostic procedures have to be directed towards the prevention of irreversible changes. In this respect, patients using chloroquine have to be examined at least once a year. The most sensitive methods for detecting early reversible changes are the electro-oculogram and static perimetry. The latter is probably more specific. Concerning ethambutol, the patients themselves are aware of the onset because a decrease in visual acuity and a central scotoma are early and reversible symptoms. In these cases electro-ophthalmology is of help when the diagnosis is doubtful. Iatrogenic effects of other drugs are not seen regularly in our electro-ophthalmological departments.

Chloroquine↗
PubMed1976

Visually evoked cortical potentials in the evaluation of homonymous and bitemporal visual field defects.

Visually evoked cortical potentials were studied in six patients with a homonymous and six with a bitemporal hemianopia by presenting a pattern-reversal stimulus separately to a temporal or nasal retinal area and by recording the responses from leads over the hemispheres. Homonymous visual field defects are characterized by a reduction of VECPs from the affected hemisphere. The disturbance of VECPs in bitemporal hemianopia is more serious, since the fibres from both retinal halves may be damaged by a chiasm tumour.

Evoked Potentials↗
PubMed1974

Electroperimetry.

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Amplifiers, Electronic↗