| Young-Helmholtz theory of colour vision | A theory that there are three colour-perceiving elements in the retina: red, green, and blue. Perception of other colours arises from the combined stimulation of these elements; deficiency or absence of any one of these elements results in inability to perceive that colour and a misperception of any other colour of which it forms a part. Synonym: Helmholtz theory of colour vision. (05 Mar 2000) |
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| 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) |