Márta Janáky

The scotopic low-frequency spatial contrast sensitivity develops in children between the ages of 5 and 14 years

The purpose of this study was to investigate the development of visual contrast sensitivity (CS) in children between 5 and 14 years of age. Six spatial frequencies and static (0 Hz) and dynamic (8 Hz) conditions were used at photopic and scotopic luminance levels. The results revealed significant maturation of CS, which reached the adult-like values by 11-12 years of age. The development was more pronounced at low spatial frequencies (<2 cycles/degree) and in the dynamic condition. The scotopic CS exhibited slower development than the photopic CS. These results suggest the late maturation of the magnocellular visual pathway.

Human scotopic spatiotemporal sensitivity: A comparison of psychophysical and electrophysiological data

The aim of the study was to investigate spatiotemporal visual functions under scotopic and photopic conditions in order to acquire human psychophysical and electrophysiological data that are comparable with contrast sensitivities based on single-unit recordings in animal experiments. Static and dynamic contrast sensitivities (CSs) and steady-state visual evoked potentials (VEPs) were measured under photopic and scotopic conditions in healthy volunteers. The results from the CS experiment indicated that the inclusion of temporal modulation and the application of scotopic luminance levels uniformly resulted in a relatively increased sensitivity for low spatial frequencies. Similarly, analysis of the second harmonic component of the VEPs demonstrated a shift from band-pass to low-pass functions. These results suggest that, under scotopic conditions, human visuospatial processing is characteristically predominated by the functional activity of the magnocellular pathways.

Electrophysiologic alterations in patients with optic nerve hypoplasia

The clinical and electrophysiologic data (electroretinograms and visual evoked potentials) were studied in 45 patients with optic nerve hypoplasia. The patients were divided into three fairly distinct groups on the basis of their electrophysiologic alterations. Group 1 consisted of 13 patients with almost extinguished visual evoked potentials and with mild electroretinographic alterations. These were the cases that are traditionally recognized as optic nerve hypoplasia. The serious visual impairment in these cases was accompanied by various developmental ophthalmologic and nonophthalmologic abnormalities. Group 2 included 26 patients without any significant visual evoked potential or electroretinographic alterations, but with overt funduscopic signs of optic nerve hypoplasia. These patients were consistently suffering from strabismus and/or amblyopia. The visual functions based on visual evoked potential and electroretinographic recordings could be fairly normal apart from a pathologic ophthalmoscopic picture characteristic of optic nerve hypoplasia. Group 3 included six patients with abnormal albeit well-recordable visual evoked potentials and subnormal or negative-type electroretinograms that suggested an accompanying retinal disease. This finding seems to prove that a subset of patients with optic nerve hypoplasia with nystagmus may have a primary retinal abnormality. Our study provides further evidence that optic nerve hypoplasia is not a uniform disease entity.

Severity of Autonomic and Sensory Neuropathy and the Impairment of Visual- and Auditory-Evoked Potentials in Type 1 Diabetes: Is there a relationship?

It became clear in the last decades that neuropathy is not a separate clinical entity, but a component of several related complications (1). Although the functional consequences of neuropathy are well defined in various organ systems, the relationship of the alterations in the networks of the neuronal system is still poorly documented. Assessment of the potential common alterations of the different neuronal functions in patients with diabetic neuropathy may provide new pathogenetic and diagnostic considerations. Previously, we observed correlations between the delay of certain auditory-evoked potentials and the severity of autonomic and peripheral sensory neuropathy in patients with type 1 diabetes (2). In addition, we found a relationship between the latency of visual-evoked potentials and the peripheral neuronal function (3). The aims of this study were to analyze the possible correlations between the central auditory and visual afferentations and the severity of autonomic and sensory neuropathy in patients with long-standing type 1 diabetes. A total of 10 middle-aged type 1 diabetic patients …

Visual evoked potentials during the early phase of optic nerve compression in the orbital cavity

We obtained case histories and electrophysiologic recordings from four patients with transient vision impairment due to acute orbital compression. The visual evoked potentials (VEPs) displayed alterations that depended on the size and consistency of the compressing pathology and also on the duration of the compression. This study provides evidence of the utility of the VEP in the assessment of the severity and reversibility of optic nerve lesions. The case histories also emphasized the necessity to elucidate the pathologic process of compressive lesions of the optic nerve.

Human Oscillatory Potentials: Components of Rod Origin

Oscillatory potentials (OPs) evoked by white flashing light after dark or light adaptation (WDA and WLA conditions) and those evoked by blue flashing light stimulation against a dark background (BDA condition) were recorded in 16 healthy volunteers. When blue flashing light was employed over a scotopic background, the two major OPs of this response (OP2 and OP3) appeared with a latency time that sharply coincided with the third (OP3) and fourth (OP4) components of the OPs evoked by white flashes. The results provide evidence in support of the notion that various elements of OPs represent the activities of different retinal mechanisms, of which OP3 and OP4 seem to be of rod origin.

Parallel development of contour integration and visual contrast sensitivity at low spatial frequencies

It has been suggested that visual contrast sensitivity and contour integration functions exhibit a late maturation during adolescence. However, the relationship between these functions has not been investigated. The aim of this study was to assess the development of visual contrast sensitivity and contour integration in 152 healthy volunteers aged between 5 and 30 years. The results revealed a significant maturation of contrast sensitivity at low spatial frequencies (0.5, 1.2, and 1.9 cycles/degree) and contour integration. The largest developmental step was observed for both contrast sensitivity and contour integration tasks when the 5-8-year olds were compared with the 9-11-year olds. There was a significant correlation between the development of low spatial frequency contrast sensitivity and contour integration. These results raise the possibility that the development of low spatial frequency processing may affect attentional mechanisms, which may have an impact on early contour integration.

Electrophysiological and99mTc-HMPAO-SPECT studies in Menkes disease

A diagnosis of Menkes kinky hair disease was made in two brothers who had typical clinical symptoms and laboratory findings. The older one, 11 months old at the time of diagnosis, showed an EEG pattern of low amplitude and slow waves. Visual evoked potentials (VEPs) were absent, brainstem auditory evoked potentials (BAEPs) were abnormal. Regional cerebral blood flow (rCBF) studied by hexamethylpropyleneamine oxime single photon emission computed tomography (99mTc-HMPAO-SPECT) revealed reduced blood flow in both frontal and the right temporal regions. The younger boy, followed from birth, started seizures at the age of 3 months and had a hypsarrhythmia-like EEG. BAEPs were abnormal with prolongation of the latencies at the age of 12 months, while VEPs were near normal at 6 months, but disappeared by the age of 18 months. 99mTc-HMPAO-SPECT revealed an unexpected left parietal hyperperfusion.

Interocular amplitude differences of multifocal electroretinograms obtained under monocular and binocular stimulation conditions

PURPOSE To compare the interocular amplitude differences of the multifocal electroretinograms (mfERGs) evoked by either monocular or binocular stimulation in healthy subjects with good vision. METHODS Thirty-five subjects were included in the study. A Roland Consult RETIscan system was used. DTL electrodes were employed. First, the right and left eyes were stimulated separately, then, binocular stimulation was applied. The amplitudes of the scalar products were averaged over five concentric retinal regions (rings). RESULTS The interocular amplitude differences were 21.55% (SD: ±12.72) under monocular conditions and 18.69% (SD: ±11.64) under binocular conditions. No significant differences were found between the amplitudes and variability values obtained under either monocular or binocular stimulation. CONCLUSIONS Our results provided no evidence for the advantage of either binocular or monocular stimulating conditions in obtaining mfERGs. A considerable side difference was found between the mfERGs of the two eyes in almost all individual cases.

Postnatal outcome and placental blood flow after plasmapheresis during pregnancy

Abstract Purpose: Plasmapheresis in pregnancy adversely affects maternal hemodynamics, however there are studies suggesting it to reduce pregnancy loss in immunological diseases when medication is more harmful to the fetus. The overall optimal plasmapheresis treatment protocol remains unknown. Materials and methods: A pregnant with neuromyelitis optica was followed up after receiving six volumes of fresh frozen plasma via plasmapheresis. Results: The placenta compensated the hemodynamic change until the 33rd week of gestation, resulting a small for gestational age, otherwise healthy girl. Conclusions: More research is needed on plasma exchange during pregnancy because in our observation placental circulation can adapt to the change in blood pressure.