Biomedical subjects

H A Greene

Publications and source records attributed to H A Greene.

5 recordsLinked to original sources

PubMed1992

Challenges in applying autofocus technology to low vision telescopes.

Autofocus (AF) low vision telescopes offer the potential to increase the acceptance and utilization of such low vision aids (LVA) by the visually impaired. Many patients resist conventional manual focus telescopes for a variety of reasons including appearance, field of view, weight, and utility. The elderly who comprise the significant part of the target population may also resist telescopes due to an avoidance of the technical challenge of its use. Although an AF telescope is technically advanced, it may allow for less manipulation by the wearer and hence enable its more effective application to visual tasks, especially in the near- to mid-range where depths of field narrow and the demands for focusing increase. There are many challenges involved in the application of AF technology to LVA including modification of the focusing range, signal processing for physiologically acceptable performance, and power and weight considerations. A preliminary infrared (IR) AF prototype based upon our recent work with the Ocutech Vision Enhancing System (VES) has been produced. Initial findings are presented which address the requirements of a subsequent version as well as the challenges that will be faced to optimize such a device.

Audiovisual Aids↗

PubMed1991

The Ocutech Vision Enhancing System (VES): utilization and preference study.

An NIH-sponsored user and prescriber preference trial was conducted comparing a new low vision telescope system, the Ocutech Vision Enhancing System (VES) to two conventional Keplarian spectacle telescope systems in a controlled cross-over clinical study performed at four independent low vision clinics. Fifty-five visually impaired individuals, 18-81 years of age, with both previous and no telescope experience, were followed for 8-16 weeks. The experimental and control devices were compared on a series of subject-selected visual tasks using a standardized clinical protocol. Subjects were trained in the use of the systems with standardized clinical methods. The data shows a statistically significant preference of the new design by both patient and clinician with the overriding factors relating to appearance, weight, adjustability and the fit of the frame.

Adolescent↗

PubMed1990

Comparison of the sealing ability of four obturation techniques.

This study compared the apical seal produced by four obturation techniques. The Canal Finder system was compared with lateral condensation, the Ultrafil system, and the sectional warm gutta-percha techniques. Forty-two anterior single-rooted teeth were instrumented. Ten teeth were not obturated and served as positive and negative controls. The apical seal was tested for leakage with 0.25% methylene blue dye. The teeth were shaved horizontally and dye penetration was measured with a Boley gauge. Results revealed there was no statistically significant difference among the four obturation techniques.

Analysis of Variance↗

PubMed1987

Adult age differences in visual acuity, stereopsis, and contrast sensitivity.

We investigated adult age differences in four measures of visual function: distance acuity, near acuity, stereopsis, and contrast sensitivity. Twenty-four young adults (mean age 19.5 years) and 24 older adults (mean age 68.4 years) participated. Age differences were present in each of the four measures. A stepwise discriminant analysis performed on the four measures revealed that, when the correlations among the measures were taken into account, only contrast sensitivity significantly discriminated young and older adults' performance. The strength of the correlations among the four measures was greater for older adults than for young adults. The results indicated that contrast sensitivity is a useful measure for detecting age-related changes in visual function and that a common mechanism may underlie age differences on various visual tests.

Adolescent↗

PubMedDate not supplied

From retina to response: contrast sensitivity and memory retrieval during visual word recognition.

Twenty-four young adults (M = 19.5 years) and 24 older adults (M = 68.4 years) performed a word/nonword classification task (i.e., lexical decision) in which a single letter-string was presented on each trial. Estimates were obtained of the time required to retrieve information regarding the orthography (pronounceability) and meaning of the letter-string. A measure of subjects' spatial resolution ability (contrast sensitivity) was also obtained. In the lexical decision task, the older adults' word recognition speed was slower than that of the young adults overall, but there was no age-related slowing associated specifically with the retrieval of either orthographic or semantic information. The similarity of the two age groups' retrieval estimates was independent of whether a manual or vocal response was required. An age-related change in the shape of the contrast sensitivity function was present. The age differences in the speed of word recognition, however, were not attributable to contrast sensitivity.

Adolescent↗