night vision (redirected from Thermal sight)

vision /vi·sion/ (vizh´un)

1. the sense by which objects in the external environment are perceived by means of the light they give off or reflect.

2. the act of seeing.

3. an apparition; a subjective sensation of seeing not elicited by actual visual stimuli.

4. visual acuity.

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achromatic vision  monochromatic vision.

anomalous trichromatic vision  defective color vision in which a person has all three cone pigments but one is deficient or anomalous but not absent.

binocular vision  the use of both eyes together without diplopia.

central vision  that produced by stimuli impinging directly on the macula retinae.

chromatic vision  color v.

color vision 

1. perception of the different colors making up the spectrum of visible light.

2. chromatopsia.

day vision  visual perception in the daylight or under conditions of bright illumination.

dichromatic vision  defective color vision in which one of the three cone pigments is missing; the two types are protanopia and deuteranopia.

direct vision  central v.

double vision  diplopia.

indirect vision  peripheral v.

low vision  impairment of vision such that there is significant visual handicap but also significant usable residual vision.

monochromatic vision  complete color blindness; inability to discriminate hues, all colors of the spectrum appearing as neutral grays with varying shades of light and dark.

monocular vision  vision with one eye.

multiple vision  polyopia.

night vision  visual perception in the darkness of night or under conditions of reduced illumination.

oscillating vision  oscillopsia.

peripheral vision  that produced by stimuli falling on areas of the retina distant from the macula.

solid vision , stereoscopic vision perception of the relief of objects or of their depth; vision in which objects are perceived as having three dimensions.

trichromatic vision 

1. any ability to distinguish the three primary colors of light and mixtures of them.

2. normal color vision.

tunnel vision 

1. that in which the visual field is severely constricted.

2. in psychiatry, restriction of psychological or emotional perception to a limited range.

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night vision

n.

Vision occurring in dim light.

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night vision

Etymology: AS, niht, night; L, visio, seeing

a capacity to see dimly lit objects. It stems from a chemophysical phenomenon associated with the retinal rods. The rods contain the highly light-sensitive chemical rhodopsin, or visual purple, which is essential for the conduction of optic impulses in subdued light. Night vision is sharpest at the periphery of the retina because of the concentration of rods. Night vision may be diminished by a deficiency of vitamin A, an important component of rhodopsin.

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vision

the faculty of seeing; sight.

The basic components of vision are the eye itself, the visual center in the brain, and the optic nerve, which connects the two. Abnormalities of vision in animals can only be inferred by an assessment of the animal's response to a variety of visual stimuli. The commonly used tests of vision are the menace reflex test, the watching of a moving object and the obstacle test. These can all be performed in subdued light as a test for night blindness.

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achromatic vision

vision characterized by lack of color vision.

aphakic vision

vision after lens removal.

binocular vision

the use of both eyes together, without diplopia.

central vision

that produced by stimulation of receptors in the fovea centralis.

day vision

visual perception in the daylight or under conditions of bright illumination.

double vision

diplopia.

half vision

hemianopia.

monocular vision

vision with one eye.

night vision

visual perception in the darkness of night or under conditions of reduced illumination.

panoramic vision

360° vision conferred on grazing herbivora by the lateral placement of their eyes.

peripheral vision

that produced by stimulation of receptors in the retina outside the macula lutea.

photopic vision

vision in bright illumination.

scotopic vision

vision in low illumination.

vision test

see visual acuity test.