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At least 1,729 records · Page 96Linked to original sources
PubMed2003

The role of lenticular senescence in age-related color vision changes.

PURPOSE: It has been reported that greater age-related losses in sensitivity occur for short-wavelength visual stimuli than for medium- and long-wavelength visual stimuli. The purpose of the current experiment was to determine to what extent optical, receptoral, and postreceptoral factors contribute to these age-related changes in color vision. METHODS: One hundred two observers (ages 18-87) completed a minimum motion task to determine isoluminance between red and green and between red and blue. A motion-nulling task was also performed to assess the L-M postreceptoral chromatic mechanism. RESULTS: No significant age-related changes occurred in red-green isoluminance values. Red-blue isoluminance values showed a significant and systematic decrease with age in observers with phakic eyes. Pseudophakic eyes in older subjects performed this task as well as phakic eyes in young subjects. The motion-nulling results demonstrated small age-related losses in the postreceptoral color mechanisms. CONCLUSIONS: The findings of this experiment, particularly those of the red-blue isoluminance task, indicate that the optical factor of lenticular senescence is the main contributor to the age-related changes observed in color vision. A model based on age-related changes in lenticular absorbance shows good fit with the experimental data of observers with phakic eyes, suggesting that optical factors are the main cause of the age-related changes in these color vision tasks.

Adolescent↗
PubMed1993

Caring: a vision of wholeness for nursing.

Caring as a new paradigm for nursing is rapidly gaining ascendance. As nurse scholars and practitioners recognize the power of caring, they are joining together in a "conspiracy" of caring. The purpose of this article is to set the stage for creative visioning that might generate new ways of thinking about caring, nursing practice, and research. A very brief review of caring scholarship in nursing over the last 15 years sets the context for the discussion of caring research and practice. It is suggested that when the phenomenon of interest is human caring, the perspective or vision of the scientist must necessarily change from a traditional, empirical view of what is real to a holistic vision of nursing as a human, caring science. The process for both personal and societal transformation is discussed.

Empathy↗
PubMed2003

Community care networks: linking vision to outcomes for community health improvement.

This article examines the relationship between progress toward the Community Care Network (CCN) vision and "intermediate outcomes" of 25 community-based health partnerships (CCNs). Specific components of the CCN vision were community accountability, community health focus, creation of a seamless service continuum, and managing under limited resources. Four community outcome dimensions were evaluated: access, cost, health, and quality of service delivery integration. Overall progress toward the CCN vision was significantly positively related to average intermediate outcome score and most highly correlated with two dimensions: access and quality of service integration. Qualitative analysis suggests that CCN sites accomplished the most along two dimensions--access and health--noting that intermediate health outcomes generally were in health assessment and information rather than actual health status improvement. Keys to outcome achievement appear to be (1) clearly focused intervention; (2) explicit, ongoing outcome measurement; and (3) strong integration of separate intervention components.

Community Health Services↗
PubMedDate not supplied

Quality of vision: A consensus building initiative for a new ophthalmologic concept.

PURPOSE: Many studies have addressed the quantification of visual acuity, and the conventional method of measuring it has so far demonstrated serious limitations. Vision testing requires new methods that can more precisely express the quality of vision as perceived by the patient. METHODS: This study employed the Delphi method of consensus building. Concepts associated with quality of vision (QoV) were identified by a board of experts and proposed to participating specialists in two subsequent questionnaires. Upon receipt of the completed questionnaires, the replies were classified to determine the building blocks of a consensus. RESULTS: By analyzing the replies to the two questionnaires, the authors determined the key elements of QoV on which a consensus was found among the respondents. CONCLUSIONS: A consensus was reached on the opinion that the quantification of visual acuity by traditional means is inadequate for investigating QoV. Although visual acuity is still a basic element for testing, the experts believe that contrast sensitivity, reading speed, and microperimetry are additional parameters necessary for quantifying QoV. The use of a psychometric questionnaire on visual function could allow a better interpretation of visual impairment.

Consensus↗
PubMedDate not supplied

Night vision after excimer laser photorefractive keratectomy: haze and halos.

A series of 85 patients with myopia, up to -6.00D, was treated by photorefractive keratectomy (PRK), using a 5 mm diameter ablation zone. At six months, 38 patients (45%) reported slight disturbances of night vision, nine (11%) of whom had significant problems. Perturbations of night vision after PRK are seen as starbursts and halos around lights. Corneal haze produces the starbursts, which are usually transient. In contrast, halos are myopic blur circles and may be persistent. Using a computer program, halos after PRK were found to be significantly larger than those in emmetropes and myopes corrected with spectacles (p < 0.01). The halos were diminished by using either artificial pupils or negative lens over-correction. In patients with identical bilateral PRK corrections, except for the ablation zone size, the magnitude of the halo was less with 5 mm than 4 mm zones (p < 0.01). Patients treated with 5 mm reported fewer problems attributable to halo than with the 4 mm ablation diameters (p < 0.01). Halos and pupil diameters were measured in nine patients with significant impairment of night vision haze. Those with starbursts had small hyperopic shifts, minimal halos and high haze and light scatter measurements, whilst patients with halos had large hyperopic shifts, little haze and large pupil diameters. Patients with persistent halo problems benefited from either negative lens over-correction or miotics at night.

Adult↗
PubMed2005

Reaching in children with and without developmental coordination disorder under normal and perturbed vision.

The aim of this study is to describe the reaching action of children with developmental coordination disorder (DCD) and to investigate whether their use of visual feedback during the time course of this action differs from that of normally developing children. Fifty-two children subdivided into 2 age bands (7-8 and 9-10 years) within 2 groups (with and without DCD) participated in this experiment. They were asked to reach for a target positioned either ipsilaterally or contralaterally to the reaching hand in 2 visual conditions: a condition where vision was unrestrained (normal vision) and a condition where they wore glasses with prismatic lenses (perturbed vision). An analysis of the experimental data indicates that the trajectories followed by the DCD group were longer and more curved than those of the control group. Further, the deceleration times were longer for the DCD group than for the normally developing children. The introduction of the prismatic lenses supports the idea that the use of visual feedback by children with DCD may be different from that in children without DCD.

Age Factors↗
PubMed2003

Adaptive color vision in Pullosquilla litoralis (Stomatopoda, Lysiosquilloidea) associated with spectral and intensity changes in light environment.

Some stomatopod crustacean species that inhabit a range of habitat depths have color vision systems that adapt to changes in ambient light conditions. To date, this change in retinal function has been demonstrated in species within the superfamily Gonodactyloidea in response to varying the spectral range of light. Intrarhabdomal filters in certain ommatidia within the specialized midband of the eye change spectrally, modifying the sensitivity of underlying photoreceptors to match the spectrum of available light. In the present study, we utilized Pullosquilla litoralis, a member of the superfamily Lysiosquilloidea that also has a wide depth range. Individuals were placed within one of three light treatments: (1) full-spectrum, high-intensity 'white' light, (2) narrow-spectrum 'blue' light and (3) full-spectrum, reduced-intensity 'gray' light. After 3 months, the intrarhabdomal filters in Row 3 ommatidia of the midband in blue- and gray-light-treated animals were short-wavelength shifted by 10-20 nm compared with homologous filters in animals in white-light treatments. These spectral changes increase the relative sensitivity of associated photoreceptors in animals that inhabit environments where light spectral range or intensity is reduced. The adaptable color vision system of stomatopods may allow animals to make the best use of the ambient light occurring at their habitat regardless of depth. The major controlling element of the plasticity in lysiosquilloid stomatopod color vision appears to be light intensity rather than spectral distribution.

Adaptation, Ocular↗
PubMed2006

Nocturnal colour vision--not as rare as we might think.

The dual retina of humans and most vertebrates consists of multiple types of cone for colour vision in bright light and one single type of rod, leaving these animals colour-blind at night. Instead of comparing the signals from different spectral types of photoreceptors, they use one highly sensitive receptor, thus improving the signal-to-noise ratio. However, nocturnal moths and geckos can discriminate colours at extremely dim light intensities when humans are colour-blind, by sacrificing spatial and temporal rather than spectral resolution. The advantages of colour vision are just as obvious at night as they are during the day. Colour vision is much more reliable than achromatic contrast, not only under changing light intensities, but also under the colour changes occurring during dusk and dawn. It can be expected that nocturnal animals other than moths and geckos make use of the highly reliable colour signals in dim light.

Adaptation, Physiological↗
PubMed1999

Colour vision of domestic chicks.

The colour vision of domestic chicks (Gallus gallus) was investigated by training them to small food containers decorated with tilings of grey and coloured rectangles. Chicks learn to recognise the colour quickly and accurately. Chicks have four types of single-cone photoreceptor sensitive to ultraviolet, short-, medium- or long-wavelength light. To establish how these receptors are used for colour vision, stimuli were designed to be distinguished only by specific combinations of receptors. We infer (1) that all four single cones are used, and (2) that their outputs are encoded by at least three opponency mechanisms: one comparing the outputs of ultraviolet- and short-wavelength-sensitive receptors, one comparing the outputs of medium- and long-wavelength receptors and a third comparing of the outputs of short- and long- and/or medium-wavelength receptors. Thus, the chicks have tetrachromatic colour vision. These experiments do not exclude a role for the fifth cone type, double cones, but other evidence suggests that these cones serve luminance-based tasks, such as motion detection, and not colour recognition.

Animals↗
PubMed2006

Range gated active night vision system for automobiles.

Night vision for automobiles is an emerging safety feature that is being introduced for automotive safety. We develop what we believe is an innovative new night vision system using gated imaging principles. The concept of gated imaging is described and its basic advantages, including the backscatter reduction mechanism for improved vision through fog, rain, and snow. Evaluation of performance is presented by analyzing bar pattern modulation and comparing Johnson chart predictions.

Journal Article↗
PubMed1988

Pattern and motion vision without Laplacian zero crossings.

The zero crossings of band-limited signals are known to be rich in information. Recent models of information processing in biological visual systems have proposed that image structure is represented initially by such zero crossings, after the image has been bandpass filtered at multiple scales by neural receptive fields whose two-dimensional profiles resemble the Laplacian of a Gaussian. Because the resulting zero crossings generally correspond to physically meaningful structures such as edges and occlusion boundaries, and indeed under some conditions can exhaustively specify the original image, such representations have proven useful and efficient in a variety of machine vision problems. However, some simple information-processing operations that are apparent in human pattern and motion vision can be shown to be impossible in such representations, because the zero crossings in the bandpassed signals do not capture the necessary information (at any scale of analysis), because the information that they provide is misleading, or because there are no such crossings in the signals after delta 2 G sigma filtering at any scale. Examples are provided of simple visual signal-processing tasks (texture discrimination, motion perception, pattern detection) that human beings can perform effortlessly but that cannot be performed in the proposed multiscale delta 2 G sigma zero-crossings schemes. These perceptual capabilities offer evidence against this model of early image representation in human vision.

Animals↗
PubMed1991

Two-dimensional spatial and spatial-frequency selectivity of motion-sensitive mechanisms in human vision.

Thresholds for detecting the direction of motion of drifting (8-Hz) vertical gratings [of spatial frequencies 0.1, 1.0, and 10.0 cycles per degree (c/deg)] were measured in the presence of masks that varied in both spatial frequency and orientation. Masks with different temporal properties were used. The specificity of masking was also measured for a stationary test grating of spatial frequency 3.0 c/deg. After suitable scaling and transformation, the masking data gave an estimate of the two-dimensional spatial-frequency tuning surface of cortical detector units in human vision. With the assumption of small-signal linearity and zero phase, the tuning surfaces were inverse Fourier transformed to give an indication of the size and structure of the psychophysical receptive fields of detector units. The results obtained with drifting test gratings and jittering (random phase) mask gratings indicate that motion-detector receptive fields increase in size (in cycles) with increasing spatial frequency but, at all spatial scales, have a length-width ratio of 1. These results are in close agreement with the summation results reported in J. Opt. Soc. Am. A 8, 1330 (1991). Using the same jittering mask stimuli and stationary test gratings, we confirm reports by Daugman [Vision Res. 24, 891 (1984)] and Harvey and Doan [J. Opt. Soc. Am. A 7, 116 (1990)] that motion-independent units have elongated receptive fields with a length-width ratio near 1.8. We conclude that the receptive fields of motion-dependent and -independent mechanisms in human vision are fundamentally different. The possibility that the orientation selectivity of a motion unit is sharpened by its selectivity for direction of motion is discussed.

Contrast Sensitivity↗
PubMed2006

Effects of vision and friction on haptic perception.

OBJECTIVE: Two experiments were conducted to examine the effects of vision and masking friction on contact perception and compliance differentiation thresholds in a simulated tissue-probing task. BACKGROUND: In minimally invasive surgery, the surgeon receives limited haptic feedback because of the current design of the instrumentation and relies on visual feedback to judge the amount of force applied to the tissues. It is suggested that friction forces inherent in the instruments contribute to errors in surgeons' haptic perception. This paper investigated the psychophysics of contact detection and cross-modal sensory processing in the context of minimally invasive surgery. METHOD: A within-subjects repeated measures design was used, with friction, vision, tissue softness, and order of presentation as independent factors, and applied force, detection time, error, and confidence as dependent measures. Eight participants took part in each experiment, with data recorded by a custom force-sensing system. RESULTS: In both detection and differentiation tasks, higher thresholds, longer detection times, and more errors were observed when vision was not available. The effect was more pronounced when haptic feedback was masked by friction forces in the surgical device (p < .05). CONCLUSION: Visual and haptic feedback were equally important for tissue compliance differentiation. APPLICATION: A frictionless endoscopic instrument can be designed to restore critical haptic information to surgeons without having to create haptic feedback artificially.

Adult↗
PubMed2004

Control of attention shifts between vision and audition in human cortex.

Selective attention contributes to perceptual efficiency by modulating cortical activity according to task demands. Visual attention is controlled by activity in posterior parietal and superior frontal cortices, but little is known about the neural basis of attentional control within and between other sensory modalities. We examined human brain activity during attention shifts between vision and audition. Attention shifts from vision to audition caused increased activity in auditory cortex and decreased activity in visual cortex and vice versa, reflecting the effects of attention on sensory representations. Posterior parietal and superior prefrontal cortices exhibited transient increases in activity that were time locked to the initiation of voluntary attention shifts between vision and audition. These findings reveal that the attentional control functions of posterior parietal and superior prefrontal cortices are not limited to the visual domain but also include the control of crossmodal shifts of attention.

Adult↗
PubMed2003

[Prevalence of near vision deficiency and related factors: a population-based study].

The objective of this article was to estimate the prevalence of presbyopia in adults > or = 30 years and explore associated characteristics such as demographic, socioeconomic, and individual variables. A cross-sectional, population-based study was performed with 3,007 adults > or = 30 years in Pelotas, Rio Grande do Sul, Brazil. Near vision acuity was evaluated using the Jaeger table, and other variables were investigated using standardized, pre-coded questionnaires. Prevalence of presbyopia was 54.7%. When visual acuity was measured using visual corrective means, prevalence was 29.34%. Age and female gender were associated with the outcome variable after controlling for confounding. Some 42.4% of the sample reported not requiring near vision for routine daily tasks. The conclusion was that presbyopia displays a high prevalence in the adult population and is directly related to increasing age, especially 45 years of age and appearing earlier in women. In some 30% of individuals who already use visual corrective means, the latter are ineffective for near vision.

Adult↗
PubMed2006

The effects of fatal vision goggles on drinking and driving intentions in college students.

The present study was designed to examine the effectiveness of Fatal Vision Goggles in reducing intentions to drink and drive. Participants performed a field sobriety task and drove in a traffic simulator while wearing the goggles. A regression analysis was performed in order to predict changes in intentions to drink and drive, using typical drinking patterns, perceived likelihood of getting into a collision when drinking and driving, self efficacy, and driving independence as predictor variables. Results showed that drinking and driving intentions were reduced following the use of Fatal Vision Goggles among those that typically drink more during outings, among those that believe the likelihood of collisions when drinking and driving are greater, and among those less likely to drive to achieve independence and autonomy. These results indicate that Fatal Vision Goggles can be an effective tool in altering drinking and driving attitudes among drivers with specific attitudinal and personal characteristics.

Adolescent↗
PubMed1982

Effect of movement and vision on visual-motor adjustment to optical rearrangement.

This study examined the effects of three conditions of movement (active, passive, and eye movement only) combined with two conditions of vision (sight and no sight of the body) on visual-motor adjustment to a familiar but optically rearranged environment. A total of 175 male college students were subjects. Each subject wore a pair of 25-diopter prism glasses while performing one of seven possible tasks. Visual-motor adjustment was measured by means of a mirror-box test administered prior to, and immediately following, performance of a 15-min. treatment session. Analysis of covariance indicated significant main effects for vision and a significant interaction between conditions of movement and vision. The actively moving subjects with sight of their bodies made significantly greater visual-motor adjustment to the optically rearranged environment than those in any of the other conditions investigated. The fact that non-moving subjects made small but significant adjustment was unexpected and remains unexplained.

Adult↗
PubMed1994

Effects of priority assignment of attentional resources, order of testing, and response sequence on tunnel vision.

The effects of relative priority of attentional resources allocated to simultaneous peripheral and foveal tasks, response sequence to the tasks, and order to testing with two levels of foveal cognitive loading on tunnel vision were studied with 32 Chinese undergraduates. Two levels of foveal condition were used for the foveal task while the peripheral task required a single-target detection. Performance decrement value and a significant interaction of levels x eccentricities indicated that tunnel vision was most prominent when the foveal task was primary. Greater magnitude of tunnel vision was obtained when the more difficult foveal task was tested prior to the no-foveal-load condition. Responding sequence to the tasks was nonsignificant.

Adult↗