| direct vision | Vision stimulated by an object imaged on the fovea centralis. Synonym: direct vision. (05 Mar 2000) |
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| direct vision spectroscope | <instrument> A spectroscope consisting of a single tube containing a series of prisms; one end of the tube is placed in as close contact as possible with the substance to be examined while the observer places his eye at the opposite end; it can be used to make a spectroscopic examination of the blood in vivo, as in the ear lobe or web of the thumb. (05 Mar 2000) |
| double vision | <ophthalmology, symptom> The perception of two images of a single object. Synonym: ambiopia, double vision, binocular polyopia. (18 Nov 1997) |
| indirect vision | Vision resulting from retinal stimulation beyond the macula. Synonym: indirect vision. (05 Mar 2000) |
| organ of vision | The eye and its adnexa. Synonym: organum visus, organ of vision. (05 Mar 2000) |
| oscillating vision | The subjective sensation of oscillation of objects viewed. Synonym: oscillating vision. Origin: L. Oscillo, to swing, + G. Opsis, vision (05 Mar 2000) |
| tinted vision | A condition in which objects appear to be abnormally coloured or tinged with colour; designated according to the colour seen: xanthopsia, yellow vision; erythropsia, red vision; chloropsia, green vision; cyanopsia, blue vision. Synonym: chromatic vision, coloured vision, tinted vision. Compare: dyschromatopsia. Origin: chromato-+ G. Opsis, vision (05 Mar 2000) |
| triple vision | Visual defect in which three images of the same object are seen. Synonym: triple vision. Origin: G. Triploos, triple, + opsis, sight (05 Mar 2000) |
| tubular vision | A constriction of the visual field, as though one were looking through a hollow cylinder or tube. Synonym: tunnel vision. (05 Mar 2000) |
| tunnel vision | A constriction of the visual field, as though one were looking through a hollow cylinder or tube. Synonym: tunnel vision. (05 Mar 2000) |
| twilight vision | Vision when the eye is dark-adapted. See: dark adaptation, dark-adapted eye. Synonym: night vision, rod vision, scotopia, twilight vision. (05 Mar 2000) |
| facial vision | <physiology> Sensing the proximity of objects by the nerves of the face, presumed in the case of the blind and also in sighted persons who are blindfolded or in darkness. (05 Mar 2000) |
| yellow vision | <ophthalmology> A form of chromatopsia in which objects looked at appear yellow. Origin: Gr. Opsis = vision (11 May 1997) |
| line of vision | The straight line extending from the object seen, through the centre of the pupil, to the macula lutea of the retina. Synonym: line of vision. (05 Mar 2000) |
| Abbe theory of image formation | <optics, physics> Abbe's theory is based on the fact that a non-self-luminous particle, which is illuminated by an extraneous source, gives rise to diffracted light rays, in addition to the dioptric pencil. He stated that to form a good microscopical image as many of the diffracted rays as possible should be intercepted by the objective. With closely ruled lines, his theory is easily demonstrated by observing the back lens of the objective, for here the diffracted rays can be observed directly if the aperture diaphragm is closed. It can be shown that, when the illumination is arranged to exclude the diffracted images, resolution is lost. (11 Mar 1998) |