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 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.
References in periodicals archive ?
While fasting, there was little change in retinal artery diameters during dark adaptation, but from the more constricted hyperglycemic baseline, dark adaptation was accompanied by a 2.0% increase in retinal artery diameter, from 168.0 [+ or -] 13.8 [micro]m to 171.4 [+ or -] 14.3 [micro]m at 20 min (P = 0.002) and 170.8 [+ or -] 15.0 [micro]m or 1.7% more than that before dark adaptation at 40 min (P = 0.022; Table 2).
These studies have all shown that it is the rod-mediated aspect of the dark adaptation curve which shows most significant change in AMD patients compared to those regarded as having normal ocular health.
While there are no published studies on visual function levels in CFRD subjects, there is substantial evidence that dark adaptation, (99-102) colour vision, (103,104) and contrast sensitivity104 are adversely affected in type 1 and type 2 diabetes, even in the absence of DR.
This is where all these strategies start to reinforce one another: the more comfortable you are, the more likely you'll wait long enough for dark adaptation and averted vision to really pay off.
Calia discusses telescope making, observatory siting and building, Charles Messier and his list, the magnitude scale, dark adaptation, and much more, and his explanations are pithy and well written.
Night-Vision mode gives a red display to preserve dark adaptation, but only for the star chart, not the entire screen.
Finding NGC 3172 with my 70-mm refractor was a challenge--it taxed the scope's excellent optics, my dark adaptation and averted vision, and the velvety dark sky of Northern California's Lassen Volcanic National Park, 8,200 feet above sea level.
After several hours of dark adaptation, the 10-inch Dobsonian showed the two components of the Trifid Nebula in Sagittarius with obvious nursery-room colors: pale, pastel pink and baby blue, much like the images in coffee-table astronomy books.
Dark adaptation and moderately high magnification are key to picking out this sliver of light.
To the unaided eye the limiting magnitude is 7.6 to 8.0 (with effort); the presence of Jupiter or Venus in the sky seems to degrade dark adaptation. Airglow (a very faint, naturally occurring glow most evident within about 15 of the horizon) is readily apparent.
But this method provides, at best, only a crude estimate of conditions since it can be easily skewed by variations in the individual's state of dark adaptation or visual acuity.