Search results for " vision"
showing 10 items of 2709 documents
Realignment of myocardial first-pass MR perfusion images using an automatic detection of the heart-lung interface
2004
International audience; Abstract: Magnetic resonance first-pass imaging of a bolus of contrast agent is well adapted to distinguish normal and hypoperfused areas of the myocardium. In most cases, the signal intensity-time curves in user defined regions of interest (ROI) are studied. As image acquisition is ECG-gated, the images are acquired at the same moment in the cardiac cycle, and the basic shape of the heart is similar from one view to the next. However, superficial respiratory motion can displace the heart in the short-axis plane. The aim of this study is to correct for the respiratory motion of the heart by performing an automatic realignment of the myocardial ROI based on a method t…
Influence of the luminance level on visual performance with a disposable soft cosmetic tinted contact lens.
2001
The purpose of the present work was to study the effect on visual performance of wearing disposable soft tinted contact lenses for cosmetic purposes. Parameters such as contrast sensitivity (Vistech 6000), colour vision (Farnsworth-Munsell 100-Hue colour test), visual fields (static Goldmann perimetry) and subjective vision (what the wearer feels while wearing the lenses) were studied under different illumination levels in order to check for possible vision losses while wearing these contact lenses at low illumination levels. Sixteen emmetropic subjects were fitted consecutively with seven pairs of different colour lenses (Optima Colors lenses by BauschLomb), and the experimental parameters…
The influence of scene and object orientation on the scene consistency effect
2019
Abstract Contextual regularities help us make sense of our visual environment. In scenes, semantically consistent objects are typically better recognized than inconsistent ones (e.g., a toaster vs. printer in a kitchen). What is the role of object and scene orientation in this so-called scene consistency effect? We presented consistent and inconsistent objects either upright (Experiment 1) or inverted (rotated 180°; Experiment 2) on upright, inverted, and scrambled background scenes. In Experiment 1, on upright scenes, consistent objects were recognized with higher accuracy than inconsistent ones, and we observed N300/N400 event-related potentials (ERPs) reflecting object-scene semantic pro…
Accommodative Functions with Multifocal Contact Lenses: A Pilot Study
2011
PURPOSE: To evaluate accommodative response and facility in presbyopic patients fitted with several types of simultaneous-image multifocal contact lenses (CLs). METHODS: Six presbyopic patients, unadapted wearers of simultaneous-image bifocals, were fitted with the Focus Progressives and the low- and high-addition Pure Vision simultaneous vision multifocal CLs. Each individual wore each of the three types of lenses in successive random order. Accommodative response, accommodative facility, visual acuity, and contrast sensitivity at distance and near were evaluated in all cases. A control group of eight non-presbyopic patients was also studied. RESULTS: The mean age was 28.6 +/- 2.72 and 51.…
Influence of contrast polarity on the accommodative response☆
2018
espanolObjetivo Evaluar los cambios de la respuesta acomodativa del ojo al leer un texto en diferentes condiciones de polaridad de contraste: letras negras sobre fondo blanco (condicion BoW) y letras blancas sobre fondo negro (condicion WoB). Metodos En este estudio experimental participaron dieciocho sujetos de edades comprendidas entre 21 y 41 anos. Se obtuvo objetivamente la respuesta acomodativa (AR) del ojo al leer un texto con polaridad de contraste BoW o WoB con un sistema de optica adaptativa que corregia todas las aberraciones salvo las propias del sujeto. Se estudiaron dos tamanos de letra diferentes (condiciones de agudeza visual), mostrados en una micropantalla. Se midio la AR d…
Mutation spectrum and clinical investigation of achromatopsia patients with mutations in the GNAT2 gene
2019
Achromatopsia (ACHM) is a hereditary cone photoreceptor disorder characterized by the inability to discriminate colors, nystagmus, photophobia, and low-visual acuity. Six genes have been associated with this rare autosomal recessively inherited disease, including the GNAT2 gene encoding the catalytic α-subunit of the G-protein transducin which is expressed in the cone photoreceptor outer segment. Out of a cohort of 1,116 independent families diagnosed with a primary clinical diagnosis of ACHM, we identified 23 patients with ACHM from 19 independent families with likely causative mutations in GNAT2, representing 1.7% of our large ACHM cohort. In total 22 different potentially disease-causing…
Prismatic lenses shift time perception
2009
Previous studies have demonstrated the involvement of spatial codes in the representation of time and numbers. We took advantage of a well-known spatial modulation (prismatic adaptation) to test the hypothesis that the representation of time is spatially oriented from left to right, with smaller time intervals being represented to the left of larger time intervals. Healthy subjects performed a time-reproduction task and a time-bisection task, before and after leftward and rightward prismatic adaptation. Results showed that prismatic adaptation inducing a rightward orientation of spatial attention produced an overestimation of time intervals, whereas prismatic adaptation inducing a leftward…
Facilitation of bottom-up feature detection following rTMS-interference of the right parietal cortex
2010
In visual search tasks the optimal strategy should utilize relevant information ignoring irrelevant one. When the information at the feature and object levels are in conflict, un-necessary processing at higher level of object shape can interfere with detection of lower level orientation feature. We explored the effects of inhibitory trains of transcranial magnetic stimulation (rTMS) on the right and left parietal cortex in healthy subjects performing two visual search tasks. One task (Task A) was characterised by an object-to-feature interference. The other task (Task B) was without such interference. We found that rTMS of the right parietal cortex significantly reduced reaction times (RTs)…
Multi-domain feature extraction for small event-related potentials through nonnegative multi-way array decomposition from low dense array EEG
2013
Non-negative Canonical Polyadic decomposition (NCPD) and non-negative Tucker decomposition (NTD) were compared for extracting the multi-domain feature of visual mismatch negativity (vMMN), a small event-related potential (ERP), for the cognitive research. Since signal-to-noise ratio in vMMN is low, NTD outperformed NCPD. Moreover, we proposed an approach to select the multi-domain feature of an ERP among all extracted features and discussed determination of numbers of extracted components in NCPD and NTD regarding the ERP context.
Comparison of service tactic formation on players’ movements and point outcome between national and beginner level padel
2021
The aim of this study was to analyze the influence of service tactic formation on players’ movements and point outcome at two different performance levels. The sample contained 2,148 points corresponding to 18 matches from two male padel indoor tournaments. Players were classified according to their game level: high-level (N = 36; age = 33.3 ± 6.9 years) and beginner (N = 36; age = 35.4 ± 6.8 years). Variables pertaining to service tactic formation (conventional or Australian), point outcome and movement patterns were analysed from the matches through systematic observation. The results showed how high-level players used a significantly higher percentage of the Australian formation than beg…