Explanation
Apparent size is influenced by the size of the retinal image of an object and by its apparent distance from the eyes. This is shown clearly by Emmert's law, in which the apparent size of an afterimage (e.g., the bright spot we see after looking at a camera flash) is influenced by where it is viewed. An afterimage has a fixed size on the retina, resulting from adaptation of the rod cells and cone cells of the retina. When an afterimage is viewed on the far wall of a room it looks large; when it is viewed on one's hand, it looks small. It is consistent with the geometry of the world: an object with a particular visual angle (given by the size of the retinal image) must be large if it is far away and small if it is near.
Convergence micropsia implies that the state of convergence of the eyes contributes to determining the distance of an object from the eyes, that it acts as a depth cue. At six meters, to view an object without double vision the optic axes of the eyes are essentially parallel (no convergence). At closer distances, to view an object without double vision the optic axes need to approach each other at an angle (increasing convergence). Normally, the convergence angle gives accurate information about the distance of objects. Under the conditions that yield convergence micropsia, the overconverged vergence angle specifies a shorter distance than the actual distance of the object; this affects apparent size.
Read more about this topic: Convergence Micropsia
Famous quotes containing the word explanation:
“To develop an empiricist account of science is to depict it as involving a search for truth only about the empirical world, about what is actual and observable.... It must involve throughout a resolute rejection of the demand for an explanation of the regularities in the observable course of nature, by means of truths concerning a reality beyond what is actual and observable, as a demand which plays no role in the scientific enterprise.”
—Bas Van Fraassen (b. 1941)
“There is no explanation for evil. It must be looked upon as a necessary part of the order of the universe. To ignore it is childish, to bewail it senseless.”
—W. Somerset Maugham (1874–1965)
“We live between two worlds; we soar in the atmosphere; we creep upon the soil; we have the aspirations of creators and the propensities of quadrupeds. There can be but one explanation of this fact. We are passing from the animal into a higher form, and the drama of this planet is in its second act.”
—W. Winwood Reade (1838–1875)