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:
“Auden, MacNeice, Day Lewis, I have read them all,
Hoping against hope to hear the authentic call . . .
And know the explanation I must pass is this
MYou cannot light a match on a crumbling wall.”
—Hugh MacDiarmid (1892–1978)
“Herein is the explanation of the analogies, which exist in all the arts. They are the re-appearance of one mind, working in many materials to many temporary ends. Raphael paints wisdom, Handel sings it, Phidias carves it, Shakspeare writes it, Wren builds it, Columbus sails it, Luther preaches it, Washington arms it, Watt mechanizes it. Painting was called “silent poetry,” and poetry “speaking painting.” The laws of each art are convertible into the laws of every other.”
—Ralph Waldo Emerson (1803–1882)
“Are cans constitutionally iffy? Whenever, that is, we say that we can do something, or could do something, or could have done something, is there an if in the offing—suppressed, it may be, but due nevertheless to appear when we set out our sentence in full or when we give an explanation of its meaning?”
—J.L. (John Langshaw)