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Coarse stereopsis is important for orientation in space while moving, for example when descending a flight of stairs. Fine stereopsis is mainly based on static differences. It allows the individual to determine the depth of objects in the central visual area (Panum's fusional area) and is therefore also called quantitative stereopsis.
A random-dot stereogram (RDS) is stereo pair of images of random dots that, when viewed with the aid of a stereoscope, or with the eyes focused on a point in front of or behind the images, produces a sensation of depth due to stereopsis, with objects appearing to be in front of or behind the display level.
Stereopsis is merely relative because a greater or lesser disparity for nearby objects could either mean that those objects differ more or less substantially in relative depth or that the foveated object is nearer or further away (the further away a scene is, the smaller is the retinal disparity indicating the same depth difference).
Stereoscopy creates the impression of three-dimensional depth from a pair of two-dimensional images. [5] Human vision, including the perception of depth, is a complex process, which only begins with the acquisition of visual information taken in through the eyes; much processing ensues within the brain, as it strives to make sense of the raw information.
A good procedure is a chart, analogous to the familiar Snellen visual acuity chart, in which one letter in each row differs in depth (front or behind) sequentially increasing in difficulty. For children the fly test is ideal: the image of a fly is transilluminated by polarized light; wearing polarizing glasses the wing appears at a different ...
Binocular disparity refers to the difference in image location of an object seen by the left and right eyes, resulting from the eyes' horizontal separation ().The mind uses binocular disparity to extract depth information from the two-dimensional retinal images in stereopsis.
There are two aspects of stereopsis: the nature of the stimulus information specifying stereopsis, and the nature of the brain processes responsible for registering that information. [17] The distance between the two eyes on an adult is almost always 6.5 cm and that is the same distance in shift of an image when viewing with only one eye. [17]
The patient must have fusion and stereopsis to get accurate results; It is a highly dissociative test resulting in responses being less relevant to what the patient sees in their normal daily environment, as the environment would normally be different [3] A. Lights need to be off or dimmed in order to see the dots / lights; B.