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Biomedical subjects

C T Scialfa

Publications and source records attributed to C T Scialfa.

6 recordsLinked to original sources
PubMed1992

Age differences in dynamic contrast thresholds.

Contrast thresholds for sinusoidal gratings of 1.5-18 cpd were measured in young (M = 24 years) and older adults (M = 69 years). Thresholds were determined for stationary gratings, and for gratings that traveled along a circular path at 5, 10, and 15 deg/sec. For static gratings, age differences in thresholds were greater for intermediate and higher spatial frequencies. Grating motion increased thresholds for all observers, but older adults exhibited threshold increases at lower target velocities than the young. Age differences in velocity effects were generally greater at intermediate and higher spatial frequencies. Results are discussed in relation to age changes in temporal resolution and smooth pursuit gain.

Adolescent↗
PubMed1991

Age differences in estimating vehicle velocity.

Automobile accidents among older adults may be related to difficulties in judging the speed of other vehicles. To examine this possibility, 3 groups of observers in the young adult, middle-aged, and older adult age ranges were asked to estimate the velocity of an isolated automobile traveling at 15-50 mph (24-80 kph). Across all age groups, perceived and actual velocity were related by a power function with an exponent of 1.36. Age was significantly and positively correlated with intercepts, but negatively correlated with exponents; that is, older observers showed less sensitivity to changes in actual velocity. Results bear on the issues of ontogenetic changes in accident involvement and sensitivity to motion.

Acceleration↗
PubMed1991

Reliability of the Vistech Contrast Test System in a life-span adult sample.

To assess the reliability of the Vistech Contrast Test System (VCTS), contrast sensitivity functions (CSF's) were estimated using all forms of the VCTS in 92 subjects aged 20 to 73 years, who were refracted for the test distance. Over a 3-month period, nine estimates at each spatial frequency and an equivalent number of acuity measures were obtained. The contrast sensitivity of older adults was lower than that of the younger adults, particularly at higher spatial frequencies. Practice effects which varied as a function of spatial frequency were also observed. Reliabilities for single-form estimates of contrast sensitivity (CS) were frequency-dependent, and ranged from 0.41 to 0.65. Three-form average estimates of CS yielded reliabilities ranging from 0.62 to 0.77. Consistent with the assertion that low VCTS reliabilities are due, in part, to measurement error, the reliabilities for acuity were uniformly higher than for the VCTS. Results are discussed in relation to clinical use of the VCTS across the life-span.

Adult↗
PubMed1990

Bandwidth of the contrast sensitivity function as an index of spatial vision with application to refraction.

The contrast sensitivity function (CSF), although containing more information than traditional measures of acuity, has found difficulty gaining clinical acceptance. The hesitancy of clinicians to adopt the CSF stems, in part, from the fact that it is not as readily interpreted as is acuity. In order to facilitate such interpretation, five indices of spatial vision which are derivable from the CSF were examined in a sample of 287 persons aged 5 to 85 years. All indices were found to be both age-sensitive and strongly related to each other, but bandwidth of the CSF was chosen as a practical index for clinical settings. In a second study, acuity and CSF bandwidth were measured under 0 to +/- 1 D optical blur. It was found that the correction providing best acuity also maximized CSF bandwidth, and that bandwidth was more sensitive to optical blur than was acuity. Results support the assertion that CSF bandwidth is a readily interpreted index of spatial vision that can be measured efficiently within the context of clinical refraction.

Adolescent↗
PubMedDate not supplied

Age differences in the temporal continuity of gratings as a function of their spatial frequency.

This study compared young and elderly observers on the continuity of sinusoidal grating-pairs as a function of interstimulus interval (ISI) and spatial frequency (.5, 1.0, 2.0, 4.0, 8.0, and 12.0 c/deg). Consistent with prior research, the maximum ISI over which pattern continuity was maintained increased with spatial frequency. In addition, among older observers, grating continuity occurred at significantly longer ISI's at the two lowest spatial frequencies; no age difference was observed at the higher spatial frequencies. These results could not be attributed to an age difference in retinal illumination associated with pupillary miosis. However, they do indicate an age-related decline in detecting visual offset and are consistent with the hypothesis of a decline in the effectiveness of the transient visual channels.

Adolescent↗