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PubMed1983

Flicker fusion test and occupational toxicology: performance evaluation in workers exposed to lead and solvents.

1 In a group of 108 workers professionally exposed to low lead levels and in 35 shoe factory workers exposed to a mixture of solvents, neurotoxic effects were evaluated by means of Critical Flicker Frequency, used as single test of psychophysiological performance. 2 A statistically significant lowering of CFF threshold was observed and, in the lead exposed group, this decrease is related to the biological parameter zinc protoporphyrin. 3 The usefulness of CFF measure in environmental toxicology, together with other neurophysiological tests, is considered.

Adult↗
PubMed1968

Flicker fusion phenomena.

The high-frequency temporal behavior of the human visual system has been shown to have some of the properties of a linear low-pass filter. For such a system it is appropriate to consider a repetitive stimulus as having separable Fourier harmonic components. The direct-current component or average luminance is important in that it sets the adaptation level. It is therefore convenient to keep it constant when varying other stimulus parameters, such as frequency or wave form. Of the alternating-current components, only the fundamental is important at high frequencies, the higher harmonics being relatively more attenuated. Any linear low-pass filter system responds in a predictable way to sinusoidal stimulation, whether continuous or of short duration. In the case of the visual system, predictable behavior is found at high frequencies, and it leads to discovery of hitherto unobserved pseudoflash and real flash phenomena. Measurement of a new characteristic time is suggested. At low frequencies the use of half and whole-sinusoidal flashes leads to the discovery of some interesting relations with flicker thresholds, but these remain for future discussion.

Flicker Fusion↗
PubMed1990

[Dynamics of visual functions in the conditions of glow and sodium lighting. I. Visual acuity, accommodation, flicker fusion, visual field and heterophoria].

Investigations of the functions cited in the title were performed in 23 persons with a normal visual system in conditions of equal illumination, first the glow and the next day or later--the sodium one. All the tests were carried out three times in the morning hours evaluating in this way their dynamics as the time goes. The authors are analyzing the degree of the variability of the discussed functions in the time, as well as their behaviour in conditions of applied illumination. The results obtained suggest that in conditions of illumination by a high-pressure sodium lamp no negative characteristics of this source of light emerged. Deterioration of a small degree was observed only in the range of accommodation for near.

Accommodation, Ocular↗
PubMed1983

Flicker fusion characteristics of rod photoreceptors in the toad.

Critical fusion frequency (CFF) of toad rods was examined at various intensities using intracellular recordings. Data were compared to CFF measurements (as a function of intensity) obtained with the electroretinogram (ERG) and with a horizontal cell. In all instances the rod (and rod mediated) responses produced a curve which increased monotonically to a high frequency asymptote at about 6 Hz. The curves obtained with the ERG and the horizontal cell were double branched. The upper branch exhibited a Purkinje shift and thus must have been produced by cones. Even when using a red background to suppress cone sensitivity, there was no sign of a second rod mediated branch in the CFF curves from this retina.

Animals↗
PubMed1989

The change in colour critical flicker fusion (CFF) values and accommodation times during experimental repetitive tasks with CRT display screens.

Two groups of normal subjects were loaded an experimental visual task, or a calculating and discriminating task, on a CRT display screen under different work speeds and amounts. The colour (red, green and yellow) CFF values of the subjects were measured every 15 min during the task and their accommodative function, represented by the accommodation time, was measured before and after the task. The two groups of subjects showed no significant differences in the pattern of change in the colour CFF values. The green and yellow CFF deteriorated significantly at 30 min after the start of the task. The red CFF values decreased significantly at 15 min after the start of the task and this conditions continued to the end of the task. Both groups showed a lengthening accommodation relaxation time but no change in the accommodation relaxation time after the task. This increase in the relaxation time was larger in the group of subjects who were loaded a larger amount of work at a higher speed. The results suggest that the decrease in the CFF value of the subject, particularly when the subject sees light directly using a CRT display screen, does not signify the decline in the activity or consciousness level of the brain centre alone.

Accommodation, Ocular↗
PubMed2001

The crustacean eye: dark/light adaptation, polarization sensitivity, flicker fusion frequency, and photoreceptor damage.

Compound eyes, nauplius eyes, frontal organs, intracerebral ocelli, and caudal photoreceptors are the main light and darkness detectors in crustaceans, but they need not be present all at once in an individual and in some crustaceans no photoreceptors whatsoever are known. Compound eye designs reflect on their functions and have evolved to allow the eye to operate optimally under a variety of environmental conditions. Dark-light-adaptational changes manifest themselves in pigment granule translocations, cell movements, and optical adjustments which fine-tune an eye's performance to rapid and unpredictable fluctuations in ambient light intensities as well as to the slower and predictable light level changes associated with day and night oscillations. Recycling of photoreceptive membrane and light-induced membrane collapse are superficially similar events that involve the transduction cascade, intracellular calcium, and membrane fatty acid composition, but which differ in aetiology and longterm consequence. Responses to intermittant illumination and linearly polarized light evoke in the eye of many crustaceans characteristic responses that appear to be attuned to each species' special needs. How the visual responses are processed more centrally and to what extent a crustacean makes behavioural use of e-vector discrimination and flickering lights are questions, however, that still have not been satisfactorily answered for the vast majority of all crustacean species. The degree of light-induced photoreceptor damage depends on a large number of variables, but once manifest, it tends to be progressive and irreversible. Concomittant temperature stress aggravates the situation and there is evidence that free radicals and lipid hydroperoxides are involved.

Adaptation, Ocular↗