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At least 235 records · Page 13Linked to original sources
PubMed1996

Physiological influence on ocular photometry. A review.

During the development of the ocular photometer (OPM) since 1983, we have considered several physical and physiological factors that could potentially influence the measurement and its results. Attention has been given to respiratory, circulatory, and intraocular pressure provocations, and numerous publications document the influences or lack thereof. Most recently, the authors conducted a simple reproducibility study with only 1 observer and 1 subject. Measurement of the same 2 retinal sites during a 3-week period yielded no statistically significant differences, even under relatively extreme temperature conditions. Thus, changes in readings with the OPM may be considered due to variations within the eye, such as cataract. Thus, increase in lens density may be directly and correctly expressed by dual-site measurement of retinal brightness, resulting in the contrast transfer ratio.

Cataract↗
PubMed2003

Adult brightness vs. luminance as models of infant photometry: variability, biasability, and spectral characteristics for the two age groups favor the luminance model.

When infants fail to make chromatic discriminations, do the characteristics of their performance minima coincide more closely with the properties of adult luminance matches or heterochromatic brightness matches? In addition to their spectral properties, adult luminance matches are typically characterized by relatively small individual differences, whereas brightness matches are believed to be both more variable and more biasable. Two complementary experiments were carried out on adults and 8-week-old infant subjects. Both groups were tested with small (1.5 degrees to 4 degrees ) red and blue test fields of varying luminances, embedded in a white surround. In adults, heterochromatic brightness matches were measured. Individual differences spanned about 0.5 log units, and brightness matches could be biased by as much as 0.8 log units by varying the range of test field luminances. In infants, the locations of performance minima were measured. Individual differences spanned less than 0.1 log units, the mean performance minima coincided with predictions based on V10(lambda), and the location of the performance minimum was nearly unaffected by the range of test field luminances used. Thus by all three criteria, these data suggest that infants' performance minima are mediated by luminance rather than by brightness signals. To date there remains no evidence that the infant visual system computes a brightness signal.

Adult↗
PubMed1985

A comparison of the measurement of sodium and potassium by flame photometry and ion-selective electrode.

Although sodium and potassium have been the most commonly assayed analytes by clinical chemists for many years there have been fewer analytical principles used routinely than for most other analytes. The introduction of the direct-reading ion-selective electrode has led to a re-examination of the basic concepts of the methods involved, and this in turn to a reassessment of the interpretation of the measurement of sodium in certain clinical situations. As a result there is a case for all clinical chemistry laboratories having access to a direct-reading ion-selective electrode for sodium estimation.

Biological Transport↗
PubMed1996

Frederic Ives Medal paper. History and current status of a physiologically based system of photometry and colorimetry.

The CIE chromaticity diagram, which has been in common use for more than 60 years, disguises essential relations among cone excitations that become transparent in a system developed with D. I. A. MacLeod and initially proposed by the author to the CIE in 1979. This proposal led to the formation of a CIE committee to consider an ideal version of the system, to be employed either as a supplement to, or an alternative for, the 1931 "standard observer". After 15 years, the task remains unfinished. The history of debate within the original committee and that of its successor (which is still active today) is briefly reviewed. Among cone fundamentals that might be chosen, a set derived and published by Stockman, MacLeod, and Johnson [J. Opt. Soc. Am. A 10, 2491 (1993)] is favored here, and some of the advantages for displaying visual data in a system based on these fundamentals are illustrated.

Color Perception↗
PubMed1986

Flicker photometry: residual minimum flicker.

We show that when all possible optical artifacts are eliminated in a flicker photometric procedure, there is still a residual minimum flicker after color fusion occurs. Our stimuli were alternated with approximately rectangular pulses; we obtained results contrary to those of a previous report in which the stimuli were alternated sinusoidally. In a subsidiary test using a computer-generated cosine wave on a RGB monitor, one observer perceived no residual flicker but a second observer did.

Adult↗