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At least 721 records · Page 40Linked to original sources
PubMed1984

Area-luminance relationship for a constant light peak of the standing potential in the human eye.

The area-luminance relationship of the light peak of the slow oscillation of the standing potential was investigated in man by determining luminance response curves for field sizes between 5 degrees and Ganzfeld after dark adaptation and at two levels of adaptive illumination. The luminance necessary for a low constant light peak was read therefrom and related to the area stimulated. With foveally and extrafoveally centered test lights a straight line with gradient -1 was found if the logarithm of the threshold luminance was plotted against the log area of the field. This indicates that the threshold of the light peak of the standing potential is inversely proportional to its area.

Adaptation, Ocular↗
PubMed1981

Rod-cone interaction in the dark-adapted fovea.

The foveal cone threshold was significantly lower after 45 min of dark adaptation than it was near the start of the cone plateau of the dark-adaptation curve. A concentric rod background subsequently raised the threshold by an amount correlated wit the difference between the cone plateau and the dark-adapted thresholds. Paradoxically, the rod background also lowered the cone threshold by an amount that differed from subject to subject. This sensitizing effect was identifiable by its relatively small variability across sessions. These results show that adaptation of parafoveal rods by either real light or dark light can change foveal cone thresholds.

Adaptation, Ocular↗
PubMed1994

Nonmonotonic effects of test illuminance on flicker detection: a study of foveal light adaptation with annular surrounds.

This study examined the detectability of flicker for small long-wavelength foveal test stimuli centered within larger long-wavelength surround stimuli. Flicker visibility was evaluated as a function of surround and test illuminance and as a function of test wavelength, of the time elapsed following test or surround onset, and of surround dimensions. Consistent with prior flicker threshold-versus-illuminance results [Vision Res. 26, 917 (1986)], flicker threshold decreased abruptly once the surround illuminance became sufficiently great. However, as test illuminance was increased above flicker threshold, flicker again vanished. Flicker reappeared at still higher test illuminances, as middle-wavelength-sensitive (M-) cone-mediated flicker threshold was exceeded. Meanwhile, the time required for the surround to render flicker visible increased at a rapidly accelerating rate with decreasing surround illuminance; it increased at a more sporadic rate with increasing test illuminance. At bright enough surround illuminances, flicker did not vanish with increasing test illuminance. These and other results are compatible with a framework derived from previous dark-adaptation data [Vision Res. 32, 1975 (1992)]. In that framework the test stimulus itself induces losses of flicker sensitivity by sufficiently perturbing retinal response during states or stages of adaptation that fail to cause spectrally antagonistic processes to redress that perturbation adequately. The relevant adaptation processes, which can require minutes, involve an adaptation pool that includes (and is affected by) the test stimulus.

Adaptation, Ocular↗
PubMed1996

Response of the retina at low temporal frequencies.

We investigated the low-frequency temporal response of the retina by measuring the corneal electroretinogram elicited by flickering lights. A sum of two temporal sine-wave modulations was used to generate difference frequencies between a 36-Hz standard stimulus and a series of low-frequency stimuli. The response of the retina at the difference frequency did not change as the low-frequency component of the stimulus was varied from 0.5 to 4 Hz. We also replicated an earlier study, stimulating the retina with a sum of two sine waves that were varied in average frequency but keeping the difference frequency constant. These data showed no change in the amplitude of the difference frequency as the average stimulus frequency was varied from 8 to almost 40 Hz. Taken together, the two sets of data support the notion that the in vivo early retinal response is low pass and extends without attenuation to frequencies greater than 30 Hz, in contrast to the sensitivity of the visual system measured by psychophysical techniques.

Adaptation, Ocular↗
PubMed1977

Judged brightness as a function of dark, intermediate, and light adaptation.

33 subjects were randomly assigned to a dark-, intermediate-, or light-adapted condition. They were then presented with two lighted surfaces of different brightness and asked to adjust the comparison stimulus to apparent equality with that of the standard stimulus. Results showed a significant interaction between adaptation level and stimulus intensity. The dark-adapted group showed greater accuracy at low stimulus intensities than at medium or high, while the intermediate- and light-adapted groups were more accurate in judging brightness at medium and high stimulus intensities. Differences in perceived brightness were cited as contributing to this finding.

Adaptation, Ocular↗
PubMed1975

Electrical response of the eye at varying intervals following an adapting flash exposure.

Electroretinograms (ERG) were recorded at varying intervals following an adapting flash exposure. Both amplitude and latency variations are exhibited for short interflash intervals. The ERG following the longer interflash intervals are not significantly different from the dark-adapted ERG. The relationship between the electrophysiological and psychophysical data is discussed.

Adaptation, Ocular↗