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C Owsley

Publications and source records attributed to C Owsley.

At least 19 recordsLinked to original sources
PubMed1995

Relationship between visual sensitivity and target localization in older adults.

Older adults commonly report problems in visual search tasks and experience a higher incidence of mobility problems (e.g. falls and vehicle crashes), which involve visual skills. We examined whether target localization problems in the elderly can be adequately explained by impairments in peripheral visual sensitivity, or whether deficits in higher order visual processing are also contributory. Fifty-nine older adults (59-88 yr) who exhibited varying degrees of visual field loss (none to severe) were asked to localize briefly-presented, high-contrast targets (3 x 5 deg) in the central 60 deg (diameter) of the visual field, while simultaneously performing a visual discrimination task at fixation. Visual sensitivity accounted for only 36% of the variance in localization performance across subjects, and this relationship grew weaker (13%) when the target was embedded in distracting stimuli, suggesting that impaired attentional skills also underlie older adults' localization problems. Not surprisingly, older adults with severe visual field loss were also poor at localizing targets. However, about half of those older patients with normal or near-normal visual fields also had severe localization problems. These results indicate that despite having good visual field sensitivity, many older adults have serious difficulty locating objects of interest in the environment. This study illustrates that clinical tests for identifying visual performance problems in the elderly must embody stimulus and task features which better reflect the visual demands of everyday life.

Aged↗
PubMed1994

Vision and driving in the elderly.

BACKGROUND: This is an overview of a program of research to identify visual and cognitive factors which place older drivers at risk for vehicle crashes. METHODS: A sample of 294 older drivers participated in a protocol which assessed eye health, visual sensory function (i.e., acuity, contrast sensitivity, peripheral field sensitivity), the size of the useful field of view (UFOV), and cognitive status. The sample was age- and crash-stratified to ensure inclusion of older adults covering a wide range of ages (55 to 90 years) and crash frequencies during the previous 5 years (0 to 4 crashes). The major dependent variable was the number of at-fault crashes incurred during the 5-year period before our protocol test date (retrospective study) and during the 3-year period after our test date (prospective study). RESULTS: Older drivers with visual sensory impairment, cognitive impairment, and/or a constriction in the size of the useful field of view were at greater risk for crashes than were those without these problems. The UFOV test had better sensitivity and specificity than visual sensory or mental status tests in identifying those older drivers at risk for crashes. CONCLUSIONS: The UFOV test's superior predictability is most likely due to its reliance on both visual sensory abilities and higher order attentional skills. This study suggests that interventions which reduce either visual sensory or attentional impairment may also reduce accident risk in older drivers, an issue we are currently investigating.

Accidents, Traffic↗
PubMed1993

Aging and neural spatial contrast sensitivity: photopic vision.

This study investigated the extent to which older adults' loss in spatial contrast sensitivity at a photopic level is attributable to neural changes in the aged visual system. Laser interferometry was used to generate interference fringes which bypass the optics of the eye in presenting a grating target on the retina. Older adults in good eye health exhibited on average a small but statistically significant loss (0.1-0.2 log unit) in contrast sensitivity across the spatial frequency range tested, although there was considerable overlap between young and old adults. This loss in contrast sensitivity for interference fringes accounted for less than half of the photopic contrast sensitivity loss at higher frequencies reported for older adults in studies using conventional direct-viewing techniques in which the optics of the aged eye are not bypassed. We conclude that neural changes in the aged visual system have a rather minor contribution to older adults' loss in spatial contrast sensitivity at a photopic level.

Adolescent↗
PubMed1993

Modeling the contrast-sensitivity functions of older adults.

To determine whether a parabolic template is a good description of the contrast-sensitivity functions (CSF's) exhibited by older adults, the curve-fitting method of Pelli et al. [J. Opt. Soc. Am. A 3(13), P56 (1986)] was applied to contrast-sensitivity data from 100 older subjects (ages 53-85 years). Although the method resulted in reasonable fits for most subjects, closer inspection revealed that this technique may be problematic. A significant number of observers had functions that were nonparabolic, and for many subjects the error tended to be concentrated at the peak of the CSF. In addition, in contrast to the study of Pelli et al., the peak contrast sensitivities of the subjects were only weakly related to Pelli-Robson contrast sensitivity and letter acuity. The data were also fitted with an asymmetric function of variable shape. Whereas this function provided a better fit to the nonparabolic CSF's, it resulted in inferior fits to most of the remaining data. These results demonstrate that the spatial CSF's of older adults cannot be described by a single parametric curve such as a parabola or a function of an exponential and that Pelli-Robson contrast sensitivity and letter acuity are not adequate predictors of their peak contrast sensitivities.

Adolescent↗
PubMed1993

Visual attention problems as a predictor of vehicle crashes in older drivers.

PURPOSE: To identify visual factors that are significantly associated with increased vehicle crashes in older drivers. METHODS: Several aspects of vision and visual information processing were assessed in 294 drivers aged 55 to 90 years. The sample was stratified with respect to age and crash frequency during the 5-year period before the test date. Variables assessed included eye health status, visual sensory function, the size of the useful field of view, and cognitive status. Crash data were obtained from state records. RESULTS: The size of the useful field of view, a test of visual attention, had high sensitivity (89%) and specificity (81%) in predicting which older drivers had a history of crash problems. This level of predictability is unprecedented in research on crash risk in older drivers. Older adults with substantial shrinkage in the useful field of view were six times more likely to have incurred one or more crashes in the previous 5-year period. Eye health status, visual sensory function, cognitive status, and chronological age were significantly correlated with crashes, but were relatively poor at discriminating between crash-involved versus crash-free drivers. CONCLUSIONS: This study suggests that policies that restrict driving privileges based solely on age or on common stereotypes of age-related declines in vision and cognition are scientifically unfounded. With the identification of a visual attention measure highly predictive of crash problems in the elderly, this study points to a way in which the suitability of licensure in the older adult population could be based on objective, performance-based criteria.

Accidents, Traffic↗
PubMed1993

The useful field of view test: a new technique for evaluating age-related declines in visual function.

Many older adults eventually experience difficulty in everyday visual activities, prompting them to consult with an eye care specialist. In some cases, a thorough examination may reveal no clinical basis for these difficulties. New techniques for evaluating age-related declines in visual function have substantiated the existence of deficits in visual attention that are not adequately captured by standard clinical measures, and which are predictive of real world problems in driving and mobility. These new techniques may serve an important function in guiding the diagnosis, and treatment of those older adults experiencing functional visual problems.

Activities of Daily Living↗
PubMed1993

Assessing visual function in the older driver.

It is likely that some older adults will have to be restricted from driving because of serious and irreversible deterioration in skills crucial to driving, due to vision impairment, visual attention deficits, and decreased cognitive status; however many older adults with driving difficulties can improve their driving skills or reduce their crash risk through education or training programs. Research to evaluate interventions such as those previously mentioned has high priority, given society's need to maintain the mobility and personal independence of older adults without sacrificing safety concerns.

Accidents, Traffic↗
PubMed1991

Visual/cognitive correlates of vehicle accidents in older drivers.

Older drivers have more accidents per miles driven than any other age group and tend to have significant impairments in their visual function, which could interfere with driving. Previous research has largely failed to document a link between vision and driving in the elderly. We have taken a comprehensive approach by examining how accident frequency in older drivers relates to the visual/cognitive system at a number of levels: ophthalmological disease, visual function, visual attention, and cognitive function. The best predictor of accident frequency as recorded by the state was a model incorporating measures of early visual attention and mental status, which together accounted for 20% of the variance, a much stronger model than in earlier studies. Those older drivers with a visual attentional disorder or with poor scores on a mental status test had 3-4 times more accidents (of any type) and 15 times more intersection accidents than those without these problems.

Accidents, Traffic↗
PubMed1991

Identifying correlates of accident involvement for the older driver.

Most older adults rely on the automobile to maintain their mobility and independence, in spite of the fact that age-related behavioral and biomedical changes may make driving more difficult. Indeed, accident and fatality rates begin to rise after age 55. One research goal, therefore, is to identify functional measures that differentiate older adults who drive safely from those who do not. This paper discusses conceptual and methodological issues involved in addressing this question, considers why earlier research has been largely unsuccessful, presents a working model for approaching the problem, and argues the need for large-sample, prospective research in this area.

Accidents, Traffic↗
PubMed1988

Aging, senile miosis and spatial contrast sensitivity at low luminance.

The purpose of this study was to determine how aging affects spatial contrast sensitivity at low light levels and to examine whether senile miosis, which reduces retinal illuminance in the aged eye, underlies any observed sensitivity loss. Contrast thresholds for targets having a range of spatial frequencies were measured in young (n = 13, M age = 24) and older (n = 11, M age = 73) adults who were free from identifiable ocular pathology. Measurements were carried out at three luminance levels spanning a three log unit range. Results indicated that older adults' loss in contrast sensitivity not only increased with increasing spatial frequency, but also became more pronounced with decreases in luminance level. Additional threshold measurements where pupil diameter was varied indicated that senile miosis was not responsible for older adults' loss in spatial vision at any level tested. Rather, older adults' miotic pupil tended to have a positive effect on their spatial vision in that it slightly improved their contrast sensitivity.

Adult↗
PubMed1988

Aging and luminance-adaptation effects on spatial contrast sensitivity.

Contrast sensitivity as a function of target luminance for four spatial frequencies (0.5, 2, 4, and 8 cycles/deg) was measured in younger (n = 12; age range, 19-35 years) and older (n = 11; age range, 68-79 years) adults in order to examine the feasibility of optical and neural explanations for the impairment of contrast sensitivity in older adults. All subjects were free from identifiable ocular disease and had good acuity. Sensitivity for each spatial frequency was measured at eight luminance levels spanning 3.5 log units in the photopic-mesopic range. When gratings were flickered at 0.5 Hz, functions for older adults were displaced downward on the sensitivity axis across all luminance levels, and the slopes of these functions were steeper than those for younger adults, suggesting that optical mechanisms alone cannot account for the vision loss in older adults. Further measurements, in which spatial targets were flickered at 7.5 Hz, indicated that this faster temporal modulation affected sensitivity as a function of luminance differentially in younger and older adults. These data imply that the neural mechanisms subserving human spatial vision undergo significant changes during adulthood.

Adaptation, Physiological↗
PubMed1988

'Vision through my aging eyes' revisited.

A variety of age-related changes occur in the visual system of older adults who are free from identifiable eye disease. Normal aging of the eye can affect visual functioning in older adults, and a variety of psychophysical tests have documented some of these effects. Dr. Meredith Morgan, a distinguished optometric educator, describes many of these changes in his editorial "Vision Through My Aging Eyes." In this article, an overview of several common anatomical, physiological and psychophysical changes which occur in the eye with normal aging is provided, and specific observations made by Morgan are discussed in terms of this information.

Aged↗
PubMed1987

Contrast sensitivity, acuity, and the perception of 'real-world' targets.

A major assumption underlying the use of contrast sensitivity testing is that it predicts whether a patient has difficulty seeing objects encountered in everyday life. However, there has been no large-scale attempt to examine whether this putative relationship actually exists. We have examined this assumption using a clinic based sample of adults aged 20-77 years. Contrast thresholds were measured for both: (1) gratings of 0.5-22.8 cycles/degree; and (2) real-world targets (faces, road signs, objects). Multiple regression techniques indicated that the best predictors of thresholds for real-world targets were age and middle to low spatial frequencies. Models incorporating these variables accounted for 25-40% of the variance. Although acuity significantly correlated with thresholds for real-world targets, the inclusion of acuity as a predictor variable did not improve the model. These data provide direct evidence that spatial contrast sensitivity can effectively predict how well patients see targets typical of everyday life.

Adult↗
PubMed1986

Contrast sensitivity during provoked visual impairment in multiple sclerosis.

Many patients with multiple sclerosis have subjective visual complaints that are intensified by exercise (Uhthoff's symptom). We report a case demonstrating the utility of contrast sensitivity testing in such visual complaints. Contrast sensitivity was measured before and after exercise in a multiple sclerosis patient with Uhthoff's symptom and in two healthy control subjects. A short exercise period reduced the patient's contrast sensitivity for some target sizes, but had no effect on his visual acuity; a longer exercise period produced a greater, more uniform loss of contrast sensitivity and also reduced visual acuity. Contrast sensitivities and visual acuities of the control subjects were not affected by exercise.

Adult↗
PubMed1985

Role of the crystalline lens in the spatial vision loss of the elderly.

This study examined the contribution of the crystalline lens to the spatial contrast sensitivity loss experienced by many healthy older adults. Spatial contrast sensitivity was measured in three groups of adults: older adults who had undergone cataract extraction and intraocular lens (IOL) insertion; older adults who were in good ocular health (agematched to the first group); and young adults also in good ocular health. Older adults had decreased contrast sensitivity at higher spatial frequencies compared to young adults, agreeing with earlier reports. In addition, both groups of older adults had similar contrast sensitivity at higher frequencies, contrary to what would be expected if the aged, noncataractous crystalline lens significantly hampered contrast transfer in the healthy older eye. Results imply that the crystalline lens is not primarily responsible for the spatial sensitivity loss of healthy older adults. Furthermore, these data indicate that for at least some IOL patients, spatial vision can be restored to a level similar to their agemates who have no history of lens opacity or ocular disease.

Adult↗
PubMed1984

Structural modeling of spatial vision.

A linear structural model of mechanisms underlying spatial vision was generated from the variance-covariance matrix of contrast sensitivity data. The data had been collected on a large group of observers ranging in age from 19 to 87 yr, using gratings of 0.5-16 c/deg spatial frequency. Structural models incorporating various numbers of spatial frequency-tuned mechanisms were compared, with a three-mechanism model giving the best account of the data. The same analysis was applied to contrast sensitivity data simulated from Wilson and Bergen's (1979) model. When the stimulated data covered 0.5-16 c/deg, only three mechanisms were needed to give a satisfactory account of the data; when the simulated data covered 0.25-16 c/deg, four mechanisms were required. Peak sensitivities and bandwidths of the mechanisms extracted from the simulated data resembled those extracted from the real, population data. This reinforces the idea that at an early stage of human vision a small number of spatially-tuned mechanisms are operative. In addition, the outcome of analyses with both real and simulated data illustrate the potential value of linear structural models for vision research.

Adult↗
PubMed1984

Large-sample norms for contrast sensitivity.

A portable microprocessor-controlled instrument automatically measured the static and dynamic contrast sensitivity functions (CSF's) of 265 observers for a normal population at the Dayton Air Fair and Air Force Museum. Repeat measures for six observers taken 6 months later show small, nonsystematic differences from original measurements. Median values of contrast sensitivity as well as regions encompassing 75 of 90% of our sample are shown.

Adult↗