dark adaptation

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adaptation

 [ad″ap-ta´shun]
1. a dynamic, ongoing, life-sustaining process by which living organisms adjust to environmental changes.
2. adjustment of the pupil to light.
biological adaptation the adaptation of living things to environmental factors for the ultimate purpose of survival, reproduction, and an optimal level of functioning.
color adaptation
1. changes in visual perception of color with prolonged stimulation.
2. adjustment of vision to degree of brightness or color tone of illumination.
dark adaptation adaptation of the eye to vision in the dark or in reduced illumination.
light adaptation adaptation of the eye to vision in the sunlight or in bright illumination (photopia), with reduction in the concentration of the photosensitive pigments of the eye.
physiological adaptation the ongoing process by which internal body functions are regulated and adjusted to maintain homeostasis in the internal environment.
psychological adaptation the ongoing process, anchored in the emotions and intellect, by which humans sustain a balance in their mental and emotional states of being and in their interactions with their social and cultural environments.
social adaptation adjustment and adaptation of humans to other individuals and community groups working together for a common purpose.

dark ad·ap·ta·tion

the visual adjustment occurring under reduced illumination in which the retinal sensitivity to light increases.
See also: dark-adapted eye, Purkinje shift.
Synonym(s): scotopic adaptation

dark adaptation

n.
The physical and chemical adjustments of the eye, including dilation of the pupil and increased activity of rods in the retina, that make vision possible in relative darkness.

dark′-a·dapt′ v.
dark′-a·dapt′ed (-ə-dăp′tĭd) adj.

dark adaptation

a normal increase in sensitivity of the retinal rod cells of the eye to detect any light that may be available for vision in a dimly lighted environment. The process is accompanied by an adjustment of the pupils to allow more light to enter the eyes.

dark ad·ap·ta·tion

(dahrk ad'ap-tā'shŭn)
The visual adjustment occurring under reduced illumination in which the retinal sensitivity to light is increased.
See also: dark-adapted eye
Synonym(s): scotopic adaptation.

dark adaptation

The gradual acquisition of the ability to see in dim light that normally occurs in conditions of poor illumination. Dark adaptation becomes defective (night blindness) in vitamin A deficiency because this vitamin is necessary for the production of retinal VISUAL PURPLE. Poor dark adaptation is also a feature of RETINITIS PIGMENTOSA (tapetoretinal degeneration).

dark adaptation

the increase in light sensitivity of an eye as a result of remaining in the dark, being the time taken for rods to re-form rhodopsin. In total darkness it takes 30 minutes for the rods to adapt and the eye to achieve maximum sensitivity.

adaptation

1. adjustment of the pupil to light, constricting with increased light intensity, dilating with decreased intensity.
2. any anatomical, physiological, developmental or behavioral adjustment to the environment of an organism which enhances its chances of leaving descendants. The ability of animals to adapt to a limited supply of drinking water and to high or low environmental temperatures is an important aspect of animal husbandry. The selection of animals which are capable of a high level of such adaptation has made it possible to improve the productivity of herds and flocks in some countries. See also general adaptation syndrome.
3. the process by which organisms are modified so as to improve their chances of survival in an environment.

dark adaptation
adaptation of the eye to vision in the dark or in reduced illumination.
light adaptation
adaptation of the eye to vision in sunlight or in bright illumination (photopia), with reduction in the concentration of the photosensitive pigments of the eye.
negative adaptation
adaptation rate
the rate at which afferent sensory receptors discharge into their afferent axons. The rates differ between different types of receptors. For example, there are slow adaptors which signal the more persistent changes such as steady pressure. See also receptor adaptation (below).
receptor adaptation
sensory receptors vary in their individual response to stimuli, the response declining after an initial period of rapid response. The rate at which different kinds of receptors change these responses is the adaptation rate (see above).