PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Adaptation, Ocular”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1978

The cerebellar control of accommodation of the eye in the cat.

The effect of cerebellar stimulation on the accommodation of the lens was examined in anesthetized cats. An infrared optometer was used to measure the refractive power of the lens during stimulation of the cerebellum. The area giving responses within latencies shorter than 160 msec and amplitudes larger than 0.15 diopters is localized in the contralateral interpositus and fastigial nuclei and the ipsilateral interpositus nucleus. No responses could be evoked by stimulating the bilateral lateral nuclei. Accommodation responses were also evoked by cerebellar cortex stimulation. Accommodation responses evoked by stimulating the cerebellar nuclei were inhibited by preceding cerebellar cortical stimulation.

Accommodation, Ocular↗
PubMedDate not supplied

A review of age changes in perceptual information processing ability with regard to driving.

Age related changes in the sensory modalities of hearing and vision, along with changes in the information processing abilities of selective attention, perceptual style, and perceptual-motor reaction time, were reviewed in the context of driving behavior. Literature reported, indicated age related changes in these abilities have relevance for the understanding of the driving behavior of the older adult.

Accommodation, Ocular↗
PubMedDate not supplied

[Adaptation in a detector system and differential sensitivity].

It is shown, that if during adaptation the sensitivity of single detectors of the models (1) is constantly decreasing proportionally to the level of their excitation, then the differential sensitivity of the whole system to the stimulus near the adapting stimulus increase. The condition is deduced under which the perceived value of stimulus parameter is invarable during adaptation. Calculated from these conditions invariable values of line inclination, hue of the patch, are in agreement with experimentally obtained data.

Adaptation, Ocular↗
PubMed1979

After-effects of small adapting fields.

1. Sensitivity to a small test probe in the centre of a small, steady background is less than when the background is large (sensitization). When an equiluminous steady annulus is added to the region surrounding a small background, rod threshold takes several minutes to stabilize at its new, lower level. The after-effects of the small background follow a time course characteristic of cortical adaptation. 2. The sensitivity loss and time course of recovery after intense bleaching lights in the cone system depend markedly on the size of the retinal region bleached, although no such effect is observed in the rod system. If a steady annular surround is added to the region surrounding the bleached patch, threshold falls rapidly to the value it would have after a large-area bleach of the same intensity. 3. The interaction between bleaches and steady surrounds suggests that bleaches produce long-lasting signals in the cone receptors. 4. The different temporal properties of sensitization on rod backgrounds and sensitization after cone bleaches suggest that different mechanisms underlie the two phenomena. 5. In cone vision, if light is added to the area surrounding a small, steady background, the subsequent readjustment takes minutes to complete, as it does in rod vision. But in addition, for cones, a large proportion of the sensitivity loss caused by the small background can be rapidly restored, as it is with cone bleaches. 6. The above results, together with the known absence of sensitization in rod dark adaptation, are consistent with the hypothesis that sensitization occurs at least partly at the retinal level in the cone system, but not (or only weakly) in the rod system, and that there is an additional, probably cortical elevation, common to rod and cone systems, for small backgrounds, but not for small, brief bleaches.

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↗
PubMed1977

Increased intracellular sodium mimics some but not all aspects of photoreceptor adaptation in the ventral eye of Limulus.

The effects of the intracellular iontophoretic injection of Na+ ions have been quantitatively compared with adaptation in ventral photoreceptors of Limulus. We find that: (a) both light adaptation and sodium injection are associated with a decrease in the variability of the threshold response amplitued; (b) both light adaptation and sodium injection are associated with a decrease in the absolute value of the temporal dispersion of the threshold response time delay; (c) the same template curve adequately fits the intensity response relationships measured under light adaptation and Na+ injection; (d) both light adaptation and Na+ injection produce a fourfold decrease in response time delay for a desensitization of 3 log units; (e) the time coures of light adaptation and dark adaptation is significantly faster than the onset of and recovery from desensitization produced by Na+ injection; (f) unlike local illumination, Na+ injection does not produce localized desensitization of the photoreceptor. These findings suggest that a rise in intracellular Na+ concentration makes at most only a minor contribution (probably less than 5%) to the total adaptation of these receptors in the intensity range we have examined (up to 3 log units above absolute threshold). However, changes in intracellular Na+ concentration may contribute to certain components of light and dark adaptation in these receptors.

Action Potentials↗
PubMed1976

Effects of light and dark upon photoreceptor synapses in the retina of Xenopus laevis.

Photoreceptor synapses in Xenopus retina were studied after exposure to day/night cycles and continuous light or dark. In the rods, dense-core vesicles appear alongside the synaptic ribbons in animals exposed to light. In dark-adapted rods, electron-dense material is present in the synaptic clefts, but no dense-core vesicles are found associated with the synaptic ribbons. Cone photoreceptors do not show these ultrastructural changes in response to light and dark. Prolonged exposure to light (21 days) causes flattening of the synaptic vesicles associated with the synaptic ribbons in both rods and cones. The results are discussed in the light of what is known about transmitter release from photoreceptors.

Adaptation, Ocular↗