PubMed Health⌕ Search

Biomedical subjects

J A Brabyn

Publications and source records attributed to J A Brabyn.

9 recordsLinked to original sources
PubMed2001

Reading performance in older adults with good acuity.

PURPOSE: This study evaluated factors affecting reading performance in a sample (N = 544) of older adults (mean age 72.8 years, range 58 to 102) with good high-contrast acuity (> or = 20/32). METHODS: Using the Pepper Reading Test, the relationship between reading rate and several vision measures was assessed. RESULTS: Mean corrected reading rate fell substantially over the age range tested despite the fact that these individuals all had good acuity. However, multiple regression analysis indicated that when other measures were taken into account (most notably, low-contrast vision, motor ability, and attentional field integrity), age was not a significant independent predictor of corrected reading rate. CONCLUSION: Reading is an important skill, and ways of enhancing reading performance should be explored. Good high-contrast acuity does not assure that older individuals can read satisfactorily.

Aged↗
PubMed2000

Ocular contributions to age-related loss in coarse stereopsis.

PURPOSE: To determine the basis for the dramatic decline in coarse stereopsis that occurs with age. METHODS: The Frisby test was used to assess stereopsis in a large sample of randomly selected persons over the age of 58 years. A number of other vision functions were also assessed in the same persons. The data were used to address the question of whether the decline in stereopsis reflects age-related alterations in cortical stereopsis mechanisms themselves (e.g., disparity detectors) or a degradation of the signal reaching the cortex as a result of alterations in earlier visual components. Two of three vision measures were binocular and thus reflect predominantly the function of the better eye. RESULTS: We find, as many others have reported, that even very coarse stereopsis declines dramatically with age. Despite not having separately assessed each eye, we find that among those selected to have good ocular function there was no significant decline in coarse stereopsis with age. CONCLUSION: These findings suggest that the enormous decline in coarse stereopsis with age can be accounted for by alterations in early stages of vision processing.

Aged↗
PubMed2000

The relation between visual acuity and other spatial vision measures.

PURPOSE: To examine to what extent measurement of standard visual acuity allows prediction of other spatial vision measures on an individual basis when high correlations exist between visual acuity and the other measures. METHODS: A series of spatial vision functions were measured in a sample of 900 community-dwelling older observers. Regression analysis was performed, and correlation coefficients were calculated between standard high-contrast visual acuity and other spatial vision measures including contrast sensitivity, low-contrast acuity, low-contrast low-luminance acuity (SKILL card), and disability glare acuity. RESULTS: All measures were highly and significantly correlated with standard visual acuity (r = 0.68 to 0.91). Despite the high correlations, many predictions of the other spatial vision measures from the correlation with standard acuity fell considerably outside of acceptable ranges determined by repeatability. The influence of the range of values in correlations is emphasized. CONCLUSIONS: Other spatial vision measures cannot be predicted on an individual basis from visual acuity despite high and significant correlations between the measures.

Aged↗
PubMed1999

Seeing into old age: vision function beyond acuity.

PURPOSE: To provide a comprehensive description of vision function beyond acuity in older individuals. METHODS: A sample of 900 individuals between the ages of 58 and 102 years (mean age of 75.5) was binocularly tested wearing habitual correction on a battery of psychophysical tests including high and low contrast acuity, low contrast low luminance acuity, disability glare, contrast sensitivity, color vision, stereoacuity, recovery from glare, and attentional visual fields. RESULTS: High contrast acuity is reasonably well maintained on average, even into very old ages. Spatial vision measures under conditions of reduced contrast or luminance, or glare reveal significant impairment in a large portion of the aged. Many older individuals also have greatly reduced stereopsis, poor color discrimination, and severely restricted peripheral fields under conditions of divided attention. A single exponential function relating performance to age fits all spatial vision data sets. The function for individual spatial measures lies at different positions along the age scale. The derived aging function with a time constant of approximately 15 years also fits results from other recent aging studies of acuity and contrast sensitivity. CONCLUSIONS: Standard visual acuity underestimates the degree of vision function loss suffered by many older individuals under the nonoptimal viewing conditions encountered in daily life. All spatial vision functions show a similar rate of decline with age of the population, but the age at which decline begins varies among measures.

Aged↗
PubMed1982

Locomotion of the blind controlled by natural sound cues.

Measures of the accuracy of locomotion control were taken with blind and blindfolded sighted subjects using the natural auditory obstacle sense to locate a travel path. These measures were compared with the accuracy of visual guidance. While the blind show a greater skill than blindfolded sighted subjects in using auditory cues for guidance, auditory guidance is notably inferior to visual guidance and deteriorates markedly when smaller targets are used to define the travel path. The natural obstacle sense thus appears to give only a rudimentary perception of the presence of objects and does not provide sufficient spatial information to allow accurate locomotion control.

Adult↗
PubMed1981

Use of foreground and background information in visually guided locomotion.

The effects of reducing the range of spatial perception on the accuracy of visually guided locomotion were studied in two experiments. Limiting the range of perception to only near objects produces changes in the flow of stimulus detail and reduces opportunities for the appearance of an aiming point and for motion parallax. Such conditions were found to produce inferior performance compared to full vision, or to minimal background information. A defined aiming point was also found to assist control when no other background was present. The results are discussed with reference to theories of locomotor control and the design of artificial spatial sensing aids for the blind.

Depth Perception↗