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Biomedical subjects

J Tucker

Publications and source records attributed to J Tucker.

At least 127 records · Page 7Linked to original sources
PubMed1980

Depth-of-focus of the pseudophakic eye.

Pseudophakic patients have been found with the ability to read both 6/6 and N5 without a reading addition. An explanation of this phenomenon is offered in terms of the depth-of-focus of the pseudophakic eye. Results of experiments to measure the depth-of-focus of the pseudophakic eye for Snellen letters are compared with theoretical predictions from earlier work, and implications in terms of visual acuity and refractive error are discussed.

Cataract↗
PubMed1979

Reaction and response times for accommodation.

Using an infra-red dynamic optometer, a qualitative comparison of the accommodation responses of two observers to step changes in target position showed marked differences in their ability to accommodate correctly. Measurement of reaction time (or latency) gave results comparable with those of other workers and independent of target position. Measurements of response time showed for one observer that the response time was dependent on the extent of the accommodative change required; this was not true of the other observer. Possible reasons for the intersubject differences and the role of the instructions given to the observer are discussed.

Accommodation, Ocular↗
PubMed1978

Accommodation as a function of object form.

The steady-state, monocular accommodation resposne to sinusoidal grating targets was assessed as a function of the spatial frequency of the grating and its vergence at the eye, using a laser optometer. At all levels of accommodative stimulus, the response was found to be dependent on grating frequency. At very low frequencies, the response was often substantially in error and was closely related to the accommodation exercised by the observer when viewing an empty field. At higher frequencies, the response became more accurate. Possible models for accommodative strategies underlying the experimental results are discussed. A model involving dynamic evaluation of the changes in retinal-image modulation produced by accommodation fluctuations for many features of the observations.

Accommodation, Ocular↗
PubMed1978

Accommodation and color.

Previous studies of the effects of color on the accommodation response are reviewed. The monocular, steady-state response to targets under various colors of illumination is investigated. It is shown that trained observers change their level of accommodation, when viewing a target at a constant distance, to compensate for the varying ocular longitudinal chromatic aberration as the color of the target is changed. Untrained subjects, however, may initially show inconsistent responses. Results in white and greeen are closely comparable. Dynamic aspects of these effects are illustrated and it is shown that the ocular longitudinal chromatic aberration increases slightly with accommodation. The results are related to current ideas on the accommodative system.

Accommodation, Ocular↗
PubMed1975

The depth-of-focus of the human eye for Snellen letters.

Snellen acuity is determined as a function of refractive error for two subjects under cyploplegia, using randomised test charts, constant test chart luminance and a series of artificial pupils. These results allow determination of the depth-of-focus of the eye for Snellen targets, and it is shown that both optical and retinal factors influence the depth-of-focus achieved. Depth-of-focus is found to increase with decreasing pupil diameter and visual acuity. The clinical significance of these results, particularly with respect to the precision with which refractive error may be determined, is discussed.

Accommodation, Ocular↗
PubMed1975

Fabrication of a polysar, temporary prosthesis in a hospital setting.

The Physical Therapy Department at Kessler Institute for Rehabilitation has been fabricating temporary prostheses since 1967. Initially, these below-knee limbs were constructed with a plaster socket attached to a modular type prosthesis. Early in 1970, we began to use polysar, a thermoplastic compound. It is nonirritating to the skin, light, durable, easily moldable, relatively inexpensive, retains suspension mechanisms adequately, and allows the production of a cosmetically acceptable training limb. Because we had difficulty with the direct forming method as described by Staros and Gardner, the indirect method was adopted.

Amputation Stumps↗
PubMedDate not supplied

Angiotropic large cell lymphoma (ALCL): morphological, immunohistochemical and genotypic studies with analysis of previous reports.

The entity 'angioendotheliomatosis proliferans systemisata' was first described 28 years ago as a cutaneous small vessel neoplasm of presumed endothelial origin. Since then, 101 similar cases have been reported under a variety of different names, most with systemic as well as cutaneous lesions, and a lymphoid histogenesis of the tumour cell is now favoured. Review of these cases has shown a characteristic clinical presentation with predominant neurological and dermatological features, although the diagnosis was made at autopsy in 53 per cent of patients. Most therapeutic regimens have proved ineffective with a median survival of 5 months from date of clinical presentation. Aggressive combination chemotherapy can produce complete and lasting remission and a partial response to steroids is sometimes seen. We have examined a case of this condition showing unusual clinical features. Immunohistochemical studies confirm the lymphoid origin of the tumour cells with B cell phenotype. Antigen receptor gene rearrangement studies indicate the presence of the same clonal population of B cells in multiple sites. We suggest that the term 'angioendotheliomatosis proliferans systemisata' should be dropped and support the use of 'angiotropic large cell lymphoma' to describe this unusual condition.

B-Lymphocytes↗