Topic
Contrast (vision)
About: Contrast (vision) is a research topic. Over the lifetime, 10379 publications have been published within this topic receiving 221480 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: Average reduction in reading speed caused by a difference in letter contrast between 100% and 20% is significantly more apparent in patients with glaucoma when compared with visually healthy people with a similar age and similar cognitive/reading ability.
Abstract: Purpose.Past research has not fully ascertained the extent to which people with glaucoma have difficulties with reading. This study measures change in reading speed when letter contrast is reduced, to test the hypothesis that patients with glaucoma are more sensitive to letter contrast than
69 citations
TL;DR: The smooth pursuit motor response shows the same kind of slowing at low contrast that was demonstrated in previous studies on perception.
Abstract: Summary of results We have shown that smooth pursuit eye velocity gain increased as a function of contrast, but there are different effects of contrast depending on target speed. At a slow target velocity, there is a linear increase in pursuit gain with increasing contrast across all contrast levels. This result is in line with psychophysical effects of relative velocity judg-ments with contrast at low speeds. For faster target veloci-ties (> 1 deg/s), there is a steep rise in gain as contrast rises above two to three times threshold. The effect of contrast then saturates, but there is still a small increase even at the highest levels of contrast. The effect of contrast is therefore small at higher contrast levels and large at low-contrast lev-els. Velocity estimation and smooth pursuit eye movement characteristics were also affected by changes in spatial fre-quency, but the effect was unsystematic. Comparison with previous studies Our results are in general agreement with previous studies on the effect of contrast on perception and smooth pursuit. Perceptual slowing has been reported to be more pronounced in slowly moving stimuli (Stone & Thompson, 1992; Thompson, 1982). Hawken and Gegenfurtner (2001) found a reduction in eye velocity with decreasing contrast for first-order motion targets, but only for slow targets mov-
69 citations
TL;DR: Vernier thresholds were affected by both grating contrast and spatial frequency, and most of the data are consistent with the predictions of Wilson's [(1986) Vision Res. 26, 453-469] model.
69 citations
TL;DR: Methods for calculations and measurements of the STAR, scattering-to-attenuation ratio, for quantification of the effectiveness of the contrast agent and comparison between different contrast agents are presented.
Abstract: A standardization procedure for in vitro acoustic characterization of ultrasound contrast agents is presented. One new acoustic parameter for particular importance is retained: This is STAR, scattering-to-attenuation ratio, for quantification of the effectiveness of the contrast agent. The STAR expresses the ability of the contrast agent to enhance the visualization of the tissue containing the contrast agent and, at the same time, represents the degree of its absorption. So, it is desirable to produce a contrast agent with high STAR, having good scattering properties to improve the image visualization, and low attenuation to image the underlying biological structures and to avoid shadowing. In this study, we present methods for calculations and measurements of the STAR and comparison between different contrast agents.
69 citations
TL;DR: The results suggest that visual acuity, contrast sensitivity, and stereo acuity impairments may be risk factors for cognitive decline.
Abstract: Background An association between visual impairment and cognitive outcomes has been documented, but there is limited research examining this relationship using multiple measures of vision. Methods Participants included non-demented individuals in Year 3 of the Visual impairment was assessed using visual acuity, contrast sensitivity, and stereo acuity. Cognitive function was defined using the digit symbol test and the Modified Mini-Mental State Examination (3MS). Incident cognitive impairment was defined as a 3MS score 5 points following Year 3. Linear mixed effects models examined longitudinal associations adjusting for year, age, sex, race, education, smoking, depression, diabetes, study site, as well as interaction terms between the vision parameters and years in study, between baseline age and years in study, and quadratic terms of baseline age and years in study. Discrete Cox regression models examined the risk of incident cognitive impairment. Results Analyses included 2,444 participants (mean age = 74). Visual acuity, contrast sensitivity, and stereo acuity impairments were not associated with statistically significant changes in annual digit symbol test scores over 7 years of follow-up, as compared to those without these impairments. However, visual acuity, contrast sensitivity, and stereo acuity impairments were associated with greater declines in annual 3MS scores over 9 years. Participants with impaired visual acuity, contrast sensitivity, and stereo acuity had a greater risk of incident cognitive impairment. Conclusions Our results suggest that visual acuity, contrast sensitivity, and stereo acuity impairments may be risk factors for cognitive decline.
69 citations