Search results for "CONTRAST SENSITIVITY"
showing 10 items of 115 documents
Luminance Information Is Required for the Accurate Estimation of Contrast in Rapidly Changing Visual Contexts.
2020
Summary Visual perception scales with changes in the visual stimulus, or contrast, irrespective of background illumination. However, visual perception is challenged when adaptation is not fast enough to deal with sudden declines in overall illumination, for example, when gaze follows a moving object from bright sunlight into a shaded area. Here, we show that the visual system of the fly employs a solution by propagating a corrective luminance-sensitive signal. We use in vivo 2-photon imaging and behavioral analyses to demonstrate that distinct OFF-pathway inputs encode contrast and luminance. Predictions of contrast-sensitive neuronal responses show that contrast information alone cannot ex…
Which Attribute of Ceiling Color Influences Perceived Room Height?
2018
Objective:We investigate effects of the hue, saturation, and luminance of ceiling color on the perceived height of interior spaces.Background:Previous studies have reported that the perceived height of an interior space is influenced by the luminance of the ceiling, but not by the luminance contrast between ceiling and walls: brighter ceilings appeared higher than darker ceilings, irrespective of wall and floor luminance. However, these studies used solely achromatic colors. We report an experiment in which we extend these findings to effects of chromatic ceiling colors.Methods:We presented stereoscopic room simulations on a head-mounted display (Oculus Rift DK2) and varied hue (red, green,…
Visual performance of the Akreos Adapt AO intraocular lens in patients with different corneal profiles measured with an adaptive optics visual simula…
2012
AIMS: To evaluate the visual performance of an aberration-free intraocular lens (IOL) in patients with different corneal profiles using adaptive optics visual simulation. METHODS: A crx1 adaptive optics visual simulator was used to simulate the aberration pattern of an aberration-free IOL combined with five corneal profiles: virgin corneas and corneas with low and high myopic ablations and low and high hyperopic ablations. Ten eyes of 10 subjects were evaluated, and monocular distance visual acuity (VA) at 100%, 50% and 10% of contrast was measured. RESULTS: At 100% of contrast, no differences were found in VA values among virgin corneas, low and high myopic ablations and low hyperopic abla…
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…
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…
Corrigendum to “Short-term changes in light distortion in orthokeratology subjects"
2015
Artigo completo publicado na revista "BioMed Research International, (2015), 1-7" e disponível no RepositóriUM em: http://hdl.handle.net/1822/33375
Contrast sensitivity and glare disability by halogen light after monofocal and multifocal lens implantation
2000
BACKGROUND—Standard examination of contrast sensitivity under conditions of glare disability is performed with incandescent light. A new halogen glare test that simulates glare as seen with oncoming vehicle headlights was used to measure glare disability in patients implanted with multifocal and monofocal intraocular lenses (IOLs). METHODS—28 patients with an average age of 69 years (SD 12 years) were implanted with a monofocal IOL (SI-40NB, Allergan) and 28 patients with an average of 66 years (12 years) were implanted with a refractive multifocal IOL (Array-SA-40N, Allergan). All patients were followed for 5 months postoperatively. Contrast sensitivity at four spatial frequencies (3, 6, 1…
Colour Constancy in Goldfish and Man: Influence of Surround Size and Lightness
2002
Colour constancy was investigated by using a series of 10 simultaneously presented surface colours ranging in small steps from green through gray to red – purple. Goldfish were trained to select one medium test field when the entire setup was illuminated with white light. In the tests, either red or green illumination was used. Colour constancy, as inferred from the choice behaviour, was perfect under green illumination when the test fields were presented on a gray or a white background, but imperfect on a black background. Under red illumination and a white background, however, colour constancy was overcompensated. Here, a colour contrast effect was observed. The influence of background l…
Reliability in perimetric multichannel contrast sensitivity measurements
2014
Background: In this study, the reliability of perimetric contrast sensitivity measurements favouring the achromatic, the red-green and the blue-yellow post-receptorial mechanisms was analysed. Methods: A new technique, multichannel ATD perimetry, provides spatial and temporal stimuli favouring the detection by an achromatic mechanism (A), from a magno or parvocellular origin or by a red-green (RG) chromatic mechanism, with a parvocellular origin or a blue-yellow (BY) mechanism, with a koniocellular origin. The repeatability and reproducibility of contrast sensitivity measurements with these stimuli were studied in a group of 40 healthy subjects. The analysis was carried out on 21 testing po…