Biomedical subjects

L P Hutman

Publications and source records attributed to L P Hutman.

7 recordsLinked to original sources

PubMed1987

Abnormal foveal spectral sensitivity in retinitis pigmentosa.

The authors measured dark-adapted foveal spectral sensitivity functions in 30 patients with retinitis pigmentosa or Usher's syndrome, whose Snellen visual acuities were 20/30 or better. An analysis of variance of the spectral sensitivity functions (normalized at 575 nm) indicated a significant reduction in the patients' relative sensitivity at 450 and 475 nm compared with a group of 15 age-similar normal observers, while the patients' relative sensitivity at middle and long wavelengths was normal. A significant negative correlation between the patients' normalized sensitivity at 450 nm and their non-normalized sensitivity at 575 nm indicated that patients with a normal absolute sensitivity at 575 nm had the greatest reduction in relative sensitivity at 450 nm. The characteristics of the short-wavelength sensitivity loss suggest that it results from an increase in the effective optical density of the yellow macular pigment, rather than from a decreased sensitivity of a specific cone mechanism or an increased lens absorption.

Adult↗

PubMed1986

Foveal cone pigment density difference and reflectance in retinitis pigmentosa.

Cone pigment density difference refers to a change in light absorption by cones before and after bleaching of their visual pigments. With a television ophthalmoscope image processor, we measured the foveal cone pigment density difference in patients with retinitis pigmentosa (RP), good central vision, and no clinically apparent foveal lesion. Foveal reflectance was obtained at 12 different wavelengths of illumination. Compared with similar-aged normal subjects, most patients with dominantly inherited RP had normal or minimally reduced cone pigment density difference within the central fovea, relatively lower than normal density difference at the foveal margin, and increased foveal reflectance. Compared with these normal subjects, patients with recessively inherited RP had significantly reduced cone pigment density difference within the central fovea, relatively more normal density difference at the foveal margin, and normal foveal reflectance.

Absorption↗

PubMed1986

Dark-adapted foveal thresholds and visual acuity in retinitis pigmentosa.

To determine the relationship of foveal absolute thresholds to visual acuity in retinitis pigmentosa, we measured thresholds in 40 patients with various forms of retinitis pigmentosa (including Usher's syndrome) whose Snellen visual acuities were 20/30 or better. At all visual acuity levels, the patients' foveal thresholds were significantly higher than those of 20 similarly aged normal observers; threshold elevations tended to be greater for a 500-nm than for a 655-nm test flash. Foveal cone spatial summation functions were normal (test flash diameter range, 7' to 1.7 degrees), indicating that the patients' threshold elevations did not result from altered summation properties. A significant correlation between foveal cone thresholds and the midpoints of the patients' Rayleigh matches demonstrated that the threshold elevations resulted in part from a decreased cone optical density.

Adolescent↗

PubMed1986

Foveal cone pigment density difference in the aging human eye.

Using fundus reflectometry, we have measured a decrease in the density difference of the foveal cone visual pigments with age in human subjects. This decrease is consistent with a loss of visual pigment in the retina with age. Fundus reflectance and normalized density difference spectra data are presented for these subjects. A decrease in cone pigment with age would be consistent with both anatomic studies, which indicate a loss and displacement of photoreceptors with age, and psychophysical studies, which demonstrate loss of photoreceptor function with age.

Adult↗

PubMed1980

Human aging and spatial vision.

The ability to see spatial structures of a wide range of sizes was measured for two groups of observers (mean ages, 18 and 73 years). All observers had good visual acuity. Although older and younger observers did not differ in ability to see targets with fine structure (high spatial frequencies), older observers were only one-third as sensitive to targets with coarse structure (low spatial frequencies) as were younger observers or to changes in criterion. Older observers were also less able than younger observers to see moving targets. The reduced sensitivity of the older observers may adversely affect routine perceptual activities, such as face recognition and visually guided postural behavior, that depend upon low spatial frequencies.

Adult↗

PubMed1980

Spatial vision and aging. I: Contrast sensitivity.

Contrast sensitivity functions (CSFs) were measured for two groups of healthy observers, a younger group with mean age 18.5 years and an older group with mean age 73 years. Although the two groups had virtually identical sensitivities to high spatial frequencies (gratings with narrow bars), the younger observers were three times more sensitive at low and intermediate spatial frequencies (gratings with wider bars) than were the older observers. Groups did not differ in relative sensitivity to gratings flickered at two rates, .33 and 6 Hz. The reduced sensitivity of older observers to low spatial frequencies cannot be explained in terms of optical factors or as the result of ocular pathology; it probably reflects a loss in that visual sub-system responsible for detecting low spatial frequency, temporally transient targets.

Adolescent↗

PubMed1980

Spatial vision and aging. II: Criterion effects.

The first paper in this series suggested that, in order to see gratings of low spatial frequency, observers in their 70s needed three times as much contrast as did observers in their 20s. Here, we use a signal detection procedure to determine if this age difference was due to actual changes in vision with age or was merely an artifact of changes in criteria for saying that a target was visible. The results show the following: older observers have a genuinely diminished ability to see gratings of low spatial frequency; older observers tend to lack confidence in their judgments of what they had seen; younger, but not older, observers grow more confident of their judgments as gratings become easier to see.

Adolescent↗