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Biomedical subjects

I Gottlob

Publications and source records attributed to I Gottlob.

71 records · Page 4Linked to original sources
PubMed1989

Reversible changes of visual acuity and pattern-electroretinograms after blue-green argon laser photocoagulation of diabetic patients.

Visual acuity, color vision, pattern-visual-evoked-potentials (P-VEPs) and pattern-electroretinograms (P-ERGs) were measured in 13 diabetic subjects before, and 24 hours and 5 weeks after blue-green argon laser treatment. As control, the same examinations were performed in 7 normal subjects and 7 diabetic patients before and after slit lamp examination with the Goldman three mirror contact lens. Visual acuity and P-ERG amplitudes were significantly reduced one day after the laser treatment, while 5 weeks after the laser coagulation, visual acuity and P-ERG amplitudes recovered to pretreatment values. The control group showed no significant changes after slit lamp examination. Since fluorescein angiography revealed no macular changes after laser treatment, the possibility of a reversible functional light damage after blue-green argon laser coagulation (ALC) is discussed.

Aged↗
PubMed1989

Comparison of contrast sensitivity between posterior chamber lenses of silicone and PMMA material.

Seventeen patients received a posterior chamber lens of PMMA in one eye and a silicone lens (Staar Surgical Co.) in the other. Contrast sensitivity was examined in both eyes in order to detect differences with respect to the material used for lens implantation. An attempt was made to exclude any changes in the eyes that were not due to lens implantation and that might possibly have an influence on the result. A paired T-test was performed for each spatial frequency. No statistically significant difference was found between the two materials with regard to contrast sensitivity.

Aged↗
PubMed1989

Effect of levodopa on the human pattern electroretinogram and pattern visual evoked potentials.

Pattern electroretinograms (P-ERGs) and pattern visual evoked potentials (P-VEPs) were recorded at three luminance levels and five different check sizes in a group of 16 control subjects before and after the oral administration of levodopa. At the lower luminance levels, significant decrease in P-ERG and P-VEP latencies were found. For P-VEPs the latency changes occurred only at small check sizes. No changes were observed in control experiments without levodopa administration. Our results show that levodopa-induced changes even occur at the retinal level and support a dopaminergic involvement in light and dark adaptation. Our observations are in agreement with a VEP delay found in Parkinson's disease and with a VEP latency increase in rats after dopamine depletion.

Administration, Oral↗
PubMed1988

Electrophysiological findings of neuronal ceroid lipofuscinosis in heterozygotes.

Nineteen obligate heterozygotes, 8 individuals at risk of being heterozygote, and 10 patients afflicted with four different forms of neuronal ceroid lipofuscinosis were examined electrophysiologically. The group of obligate heterozygotes was compared to age-matched control groups. Statistically significant differences were found between scotopic b-wave amplitudes, P-ERG amplitudes, and EOG light peaks of the obligate carriers of the juvenile type and the control subjects. The photopic L-ERGs and the latencies of the VEPs were mostly within the normal range. The findings represent the first evidence of functional ophthalmological changes in obligate carriers of neuronal ceroid lipofuscinosis and demonstrate that heterozygotes with certain hereditary autosomal recessive diseases may manifest subtle functional signs.

Adolescent↗
PubMed1988

The rabbit electroretinogram: effect of GABA and its antagonists.

Previous studies reported that the ERG b-wave is generated by changes of membrane potential of the Müller Cell, mediated by a proximal and a distal extracellular [K+] increase. From measurements with K+ sensitive electrodes there is some evidence that the proximal K+ source is generated by amacrine cell activity. It has been shown autoradiographically that in the rabbit retina GABA is located within a subgroup of amacrine cells, in interplexiform cells and horizontal cells. The effects of GABA, picrotoxin and bicuculline on the ERG of the isolated superfused retina were investigated. Picrotoxin between 10(-4) and 10(-3) M/l and bicuculline between 10(-5) and 10(-4) M/l enhanced the a- and b-wave amplitudes. The b-wave peaked at a later time and decayed at a slower rate than did the control ERG. In higher concentrations than 10(-5) M/l GABA had the opposite effect. In experiments with isolation of the PIII by means of 10(-2) M/l Aspartate or lowering of temperature to 22 degrees C, no effect of GABA on PIII could be shown. The present investigation supports participation of GABAergic cells in b-wave generation. As an underlying mechanism a proximal K+ source is assumed, which is modified by amacrine cell activity.

Action Potentials↗
PubMed1987

Pattern electroretinogram: effects of miosis, accommodation, and defocus.

The effect of miosis, lens accommodation, and defocusing on the various components of the pattern electroretinogram elicited by checkerboard reversal was investigated by employing aperture stops of different size, varying the mean luminance of the target, and inserting spherical lenses of various optical diopters in front of the eye. After topical administration of pilocarpine (1%) the following changes in the pattern electroretinogram were observed: (i) a decrease of the pupillary diameter leading to a lowered target luminance, which produced attenuation of PERG amplitudes and prolonged latencies, and (ii) defocusing by accommodation of the crystalline lens, which produced attenuation of PERG amplitudes no effect on latencies.

Accommodation, Ocular↗
PubMed1987

Alteration of visual evoked potentials and electroretinograms in Parkinson's disease.

A group of 24 patients with Parkinson's disease (PD) with normal fundi and normal visual acuities was examined electrophysiologically. Checkerboard reversal VEPs and ERGs (P-ERGs) at various contrast levels as well as photopic and scotopic luminance ERGs were recorded and compared with an age-matched group of controls. Earlier reported latency increases of the VEPs of the patients were confirmed for patterns of high contrast only. Scotopic and photopic luminance ERGs of the patients showed normal latencies, but at all light intensities the amplitudes of the scotopic and photopic b wave, as well as the amplitudes of the photopic a waves, were significantly reduced, P-ERG amplitudes were reduced at 50% contrast. Identical results were obtained in patients under dopaminergic treatment (n = 17) and in patients who did not receive any treatment (n = 7). These results suggest that alterations occur already at the retinal level where dopamine receptors have been found. Thus the reported changes of the VEP are not caused by the visual cortex alone.

Adult↗
PubMed1987

[A differential diagnostic test for optic neuritis].

A temporary lowering of body temperature by means of cold drinks, tried on a group of 18 patients with acute optic neuritis, led in 14 cases to a significant improvement in the 30 degree visual field, which the authors tested with the Octopus 201 automatic perimeter. In a group of 11 patients (17 eyes) who had previously had optic neuritis an improvement in the visual field was only seen in 8 eyes; in the other 9 eyes there was a deterioration. A slight deterioration in the 30 degree visual field after lowering body temperature was demonstrated in a group of 7 patients (12 eyes) with various diseases of the optic nerve as well as in 5 other healthy subjects. The temporary improvement in the patients with acute optic neuritis was probably caused by a reversible increase in the conductivity of the demyelinated nerve fibers as a result of lowering body temperature.

Body Temperature Regulation↗
PubMed1987

Normal pattern electroretinograms in amblyopia.

Checkerboard reversal stimuli were used to evoke transient pattern electroretinograms (P-ERGs) from the eyes of 14 patients with amblyopia and 14 normal subjects. In the control group, and in normal eyes of patients, pattern electroretinograms were obtained with monocular central fixation. Amblyopic eyes were examined by monocular and binocular fixation, and the fixation point was shifted horizontally and/or vertically until the P-ERG reached its maximal amplitude. After adjusting visual fixation, there were no significant differences in amplitude between the normal and the amblyopic eyes. In addition, the differences between both eyes were compared with the right-left eye variability of the 14 normal subjects. In the amblyopic eyes, no P-ERG abnormality was observed. These results do not support previous reports of reduced P-ERG amplitudes and are in agreement with recent findings obtained under steady-state conditions.

Adolescent↗
PubMed1986

Alterations of visual contrast sensitivity in Parkinson's disease.

Contrast sensitivity functions were determined in a population of 18 patients suffering from Parkinson's disease, and compared with the data obtained in an age-matched group of healthy controls. The controls were more sensitive at all spatial frequencies tested than the patients. The statistical comparisons were highly significant, indicating general differences between the PD patients and the controls not related to individual spatial frequency channels. When comparing the sensitivity loss between low and high spatial frequencies no significant differences were found suggesting that the decrease in contrast sensitivity is a global effect. We controlled for effects of age and cerebral atrophy, and our findings cannot be accounted for by these factors. In addition, the amount of contrast sensitivity loss was not correlated with the severity of the disease. These global functional alterations appear to be related to the reduction of dopamine at various sites of the visual system.

Adult↗
PubMed1985

Possible role of amacrine cells in the generation of the mammalian ERG b-wave.

The ERG b-wave is believed to be generated by a change of membrane potential of Müller cells mediated by alteration in extracellular K+ activity. At least two K+ sources have been suggested. From studies with K+-sensitive electrodes there is some evidence that a proximal K+ source is generated by amacrine cell activity. It has been shown autoradiographically that in the rabbit retina gamma aminobutyric acid (GABA) is located in a subpopulation of amacrine cells. Therefore the effect of GABA on the b-wave amplitude of the isolated superfused rabbit retina was investigated by double-flash stimulation. Concentrations below 10(-5) MM GABA did not change the ERG; higher concentrations diminished the b-wave amplitude. With concentrations of 10(-3) MM GABA response to the second flash was clearly less reduced than that to the first. Furthermore the time course of the ERG was altered. Our investigation supports participation of amacrine cells in b-wave generation.

Animals↗
PubMed1985

Flat preparations of ocular structures.

We employ a technique which has been used for in vitro studies of the vascular endothelium for obtaining flat preparations of different ocular structures such as corneal endothelium, epithelium of cornea, iris, ciliary body, lens and retinal pigment epithelium. The described method is relatively simple and allows evaluation of the overall state of these cellular sheets. After staining of the preparations with silver nitrate, we found intercellular lines to be present in all specimens studied except in the outer layers of the corneal epithelium. This method could be useful for in vitro studies of different pathological conditions of ocular tissues, both in animal models and in enucleated human eyes.

Animals↗
PubMedDate not supplied

Visual acuity measurements by swept spatial frequency visual-evoked-cortical potentials (VECPs): clinical application in children with various visual disorders.

Previous studies have indicated that visual acuities of normal infants can be estimated with good accuracy using swept spatial frequency visual-evoked-potentials (VECPs). In this report we describe acuity measurements obtained with this technique from 304 examinations performed on 135 children having various visual disorders. When possible, two or more different stimulation frequencies (8, 12, 15 or 24 contrast reversals/sec) were used in each patient, and three to eight sweep VECPs were obtained from each patient under each simulation and recording condition. High correlation coefficients (0.94 - 0.96) between the acuity estimated on each patient from either the single sweep giving the best visual acuity (BSS) or from vector averages (VeA) of the EEG data obtained from several sweeps confirmed previous findings in normal infants. We also found high correlation coefficients among BSS recorded at different temporal frequencies (0.79-0.97) and among comparisons of BSS or VeA acuity to optotype visual acuity (0.6-0.89). Children with clinically undetectable optokinetic responses showed lower visual acuity estimated by BSS than those who demonstrated optokinetic nystagmus. We conclude that the sweep VECP is a valid method, giving estimates of acuity which correlate well with optotype acuity and correspond well to other clinical findings, and that it can be useful in the clinical management of nonverbal patients.

Child↗