Search results for "Flicker Fusion"
showing 10 items of 17 documents
Clinical Predictors for Poor Quality of Life in Patients With Covert Hepatic Encephalopathy.
2018
Background Current EASL/AASLD guidelines recommend treatment of covert hepatic encephalopathy (HE) only in symptomatic patients, for example, in those with impaired quality of life or with affected driving abilities. Goals Because testing for impaired quality of life is time consuming, the aim of the present study was to identify simple clinical predictors for poor quality of life in patients with covert HE (CHE). Study In total, 139 cirrhotic in- and outpatients without a history of overt hepatic encephalopathy were enrolled. Diagnosis of HE grade 1 (HE1) was diagnosed clinically according to the West-Haven Criteria. Critical flicker frequency and the Psychometric Hepatic Encephalopathy Sc…
Serum nitrotyrosine and psychometric tests as indicators of impaired fitness to drive in cirrhotic patients with minimal hepatic encephalopathy
2013
BACKGROUND & AIMS: Cirrhotic patients with minimal hepatic encephalopathy (MHE) show impaired driving ability and increased vehicle accidents. The neurological deficits contributing to impair driving and the underlying mechanisms are poorly understood. Early detection of driving impairment would help to reduce traffic accidents in MHE patients. It would be therefore useful to have psychometric or biochemical parameters reflecting driving impairment. The aims of this work were as follows: (i) to shed light on the neurological deficits contributing to impair driving; (ii) to assess whether some psychometric test or biochemical parameter is a good indicator of driving impairment. METHODS: We a…
Patients with minimal hepatic encephalopathy show impaired mismatch negativity correlating with reduced performance in attention tests
2012
Attention deficit is an early event in the cognitive impairment of patients with minimal hepatic encephalopathy (MHE). The underlying mechanisms remain unclear. Mismatch negativity (MMN) is an auditory event-related potential that reflects an attentional trigger. Patients with schizophrenia show impaired attention and cognitive function, which are reflected in altered MMN. We hypothesized that patients with MHE, similarly to those with schizophrenia, should show MMN alterations related with attention deficits. The aims of this work were to assess whether (1) MMN is altered in cirrhotic patients with MHE, compared to those without MHE, (2) MMN changes in parallel with performance in attentio…
Validation of the simplified Animal Naming Test as primary screening tool for the diagnosis of covert hepatic encephalopathy
2019
Diagnosis of covert hepatic encephalopathy (CHE) is time consuming in clinical practice. Recently, a new diagnostic tool - the simplified Animal Naming Test (S-ANT1) - was presented with promising results in an Italian cohort. The aim of the present study was to validate S-ANT1 in a cohort of cirrhotic patients from a German tertiary referral centre.143 cirrhotic patients and 37 healthy controls were enrolled. Hepatic encephalopathy (HE) grade 1 (HE1) was clinically diagnosed according to the West-Haven Criteria. Critical flicker frequency and Psychometric Hepatic Encephalopathy Score were used to detect minimal HE (MHE). All participants were additionally examined by S-ANT1.58 (40.6%) pati…
Value of the critical flicker frequency in patients with minimal hepatic encephalopathy
2007
Minimal hepatic encephalopathy (MHE) is mainly diagnosed using psychometric tests such as the psychometric hepatic encephalopathy score (PHES). Despite the clinical and social relevance of MHE, psychometric testing is not widespread in routine clinical care. We assessed the usefulness of the critical flicker frequency (CFF), for the diagnosis of MHE and for the prediction of the development of overt episodes of HE. The normal range of PHES in the Spanish population was evaluated in a control group. Subsequently, 114 patients with cirrhosis and 103 healthy controls underwent both PHES and CFF tests. A diagnosis of MHE was made when the PHES was lower than −4 points. Patients were followed-up…
Focal cortical damage parallels cognitive impairment in minimal hepatic encephalopathy
2012
Little attention has been paid to cortical integrity in patients with minimal hepatic encephalopathy (MHE), although cognitive functions affected in early stages of liver disease are mainly allocated in different neocortical structures. Here we used cortical surface-based analysis techniques to investigate if patterns of cortical thinning accompany the mildest form of HE. To aim this goal, cortical thickness obtained from high-resolution 31 magnetic resonance imaging (MRI) was measured in patients with no MHE (NMHE), MHE, and healthy controls. Further correlation analyses were performed to examine whether scores in the critical flicker frequency (CFF) test, and blood ammonia levels accounte…
Fourier analysis of the stimuli for pattern-induced flicker colors.
1992
Pattern-induced flicker colors (PIFCs) were observed and color matched in rotating discs from which higher-harmonic Fourier components in the square-wave temporal luminance functions of a conventional black-and-white Benham disc had been removed. Since both reddish-brown and blue PIFCs were visible with purely sinusoidal stimuli they cannot result from differences in temporal stimulus shape or pattern and do not provide evidence for a temporal coding theory of color. Green PIFCs differed in that they did require the presence of additional harmonics. In a second experiment the luminance means upon which the sinusoidal PIFC stimuli were imposed were varied. The results show that color is dete…
Red-green flicker resolution as a function of heterochromatic luminous modulation.
1993
Critical fusion frequencies have been evaluated in heterochromatic red-green flicker as a function of red-green luminous modulation defined by mL = (R-G)/(R+G)%, at five different mean luminance levels, two test sizes (2 degrees and 5 degrees) and square wave stimuli. The extreme values mL = +/- 100 correspond to ordinary light-dark flicker (red or green); mL = 0 corresponds to pure chromatic flicker, and any other values correspond to simultaneous luminous and chromatic flicker. To implement the stimuli we have developed a new stimuli generator (AVICO, colour vision analyser) using bicolour LEDs as the light source and electronic control of the luminances and frequencies. The results for a…
Erhöhte Schwellen für die Detektion von Phasenunterschieden in musterinduzierten Flimmerfarben bei Patienten mit Glaukom
1994
BACKGROUND: Pattern-induced flicker-colors are subjective colors produced by rotating disks with black-and-white arcs. Changing the direction of rotation results in a different color. Small variations in the temporal sequence (phase differences) of the black-and-white pattern cause the colors to vary and can be perceived as color differences. PATIENTS AND METHODS: We investigated the thresholds for such phase differences in healthy (n = 11) and in glaucomatous (n = 19) eyes. Acuity and color vision were tested and in patients static visual field perimetry (Octopus G1) was carried out. The disks used for producing the pattern-induced flicker-colors were viewed from a distance of 2 m and had …
Colour vision experimental studies in teaching of optometry
2005
Following aspects related to human colour vision are included in experimental lessons for optometry students of University of Latvia. Characteristics of coloured stimuli (emitting and reflective), determination their coordinates in different colour spaces. Objective characteristics of transmitting of colour stimuli through the optical system of eye together with various types of appliances (lenses, prisms, Fresnel prisms). Psychophysical determination of mono- and polychromatic stimuli perception taking into account physiology of eye, retinal colour photoreceptor topography and spectral sensitivity, spatial and temporal characteristics of retinal receptive fields. Ergonomics of visual perce…