G. H. M. van Lith

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Studying the oscillatory potentials in diabetic retinopathy, the authors experienced several problems interpreting results of digital filtering. The main problem was the separation of the first potential from the a-wave, since their frequencies are within the same range. To improve the procedure of measuring implicit times and of calculating amplitudes, the(More)
To study the oscillatory potentials in early diabetic retinopathy the authors developed a new power measurement based on the fast Fourier transform. Three groups totalling 46 patients were examined, varying from nonvisible to preproliferative diabetic retinopathy. The oscillatory potentials expressed in microwatts were measured under scotopic and photopic(More)
Three families with Usher's syndrome were fully investigated. Special attention was paid to heterozygous manifestations of the disease. The affected members of one of these families combined complete deafness with total loss of the vestibular function. In the two others, the audiograms showed the type of partial deafness that is characteristic for Usher's(More)
Summarizing from this investigation we may conclude 1. It appeared that slight abnormalities in the nystagmograms can occur, but only in persons above 44 years of age. Because multiple sclerosis patients are usually younger than 50 years, disturbances in the nystagmogram are fairly often evidence of a brain-stem lesion. 2. In persons older than 44 years(More)
Visually evoked potentials on pattern stimulation are lowered by cataracts via scatter, absorption and defocusing. These effects have to be known before pattern stimulation can be fruitfully applied in patients when a lowered vision cannot or can hardly be explained by the cataract. It was remarkable that pattern responses were relatively good as compared(More)
In retinal detachments the scotopic ERG is generally more disturbed than the photopic ERG; both are more disturbed than would be expected from the visibly 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(More)
Recently we developed a quantitative method of measuring the Oscillatory Potentials (OP's) for a clinical study in diabetic patients. Several problems were experienced in interpreting the results obtained with digital filtering. The main dilemma was the separation of the first OP from the a-wave, since their frequencies are within the same range. The fast(More)
Delayed pattern evoked electrical cortical potentials provide a very sensitive index of clinically silent optic nerve lesions, but are not specific for multiple sclerosis. Apart from the influence of retinal illumination and of some ophthalmological diseases, delayed responses may also occur when optic nerve fibres are compressed. We observed them in Bell's(More)