Peripheral vision is part of the vision that only occurs on the side view. There is a series of non-central points in the visual field that belong to the idea of ​​peripheral vision. The "peripheral" vision refers to the area at the edge of the visual plane, the "mid-peripheral" vision is in the middle of the visual plane, and the "near-peripheral", sometimes referred to as the "para-center" vision, is adjacent to the center of the gaze.
Boundary Inside limitations
The inner limitations of peripheral vision can be defined in several ways depending on the context. In colloquial the term "peripheral vision" is often used to refer to what in technical use would be called "distant peripheral vision." This is a vision beyond the reach of stereoscopic vision. This can be understood as being restricted in the center by a circle of 60 Â ° in radius or 120 Â ° in diameter, centered around the fixation point, that is, the point at which one's view is directed. However, in general use, peripheral vision may also refer to areas outside the circle 30 Â ° within a radius or 60 Â ° diameter. In fields related to vision such as physiology, ophthalmology, optometry, or the science of vision in general, the inner limits of peripheral vision are defined more narrowly in terms of one of several regions of central retinal anatomy, generally fovea.
Fovea is a cone-shaped depression in the central retina measuring 1.5 mm in diameter, corresponding to 5 Â ° of the field of vision. The outer boundary of the fovea is seen under a microscope, or by microscopic imaging technology such as OCT or microscopic MRI. When viewed through the pupil, as in an eye exam (using ophthalmoscope or retinal photography), only the center of the fovea is visible. The anatomist calls this a clinical fovea, and says that it corresponds to the anatomy of foveola, a structure with a diameter of 0.35 mm corresponding to 1 degree of vision. In clinical use the center of the fovea is usually referred to simply as a fovea.
In terms of visual acuity, "foveal vision" can be defined as part of the retina where visual acuity is at least 20/20 (6/6 metric or 0.0 logMAR). This corresponds to a foveal avazal zone (FAZ) of 0.5 mm diameter representing 1.5 Â ° visual field. Although often idealized as a perfect circle, the central structures of the retina tend to be irregular oval. Thus, the foveal vision can also be defined as a 1.5-2 Â ° center of vision field. The vision in the fovea is generally called central vision, whereas the visions outside the fovea are called peripheries, or indirect visions.
A ring-shaped region that surrounds the fovea, known as parafovea, is sometimes taken to represent an intermediate form of vision called paracentral vision. Parafovea has an outer diameter of 2.5 mm representing the 8 Â ° field of vision. The macula, a retinal region defined as having at least two layers of ganglia (a collection of nerves and neurons) is sometimes taken as defining the peripheral vs peripheral vision limits. The macula has a diameter of 5.5 mm and corresponds to the 18 Â ° field of vision. When viewed from the pupil, as in an eye exam, only the middle of the macula is visible. Known as anatomist as a clinical macula (and in a clinical setting only as a macula), this inner region is thought to be associated with anatomical fovea.
The dividing line between near and mid peripheral visions at a 30 ° radius is based on some features of visual performance. Visual acuity decreases by about 50% every 2.5 Â ° from the center to 30 Â °, where the point of visual acuity declines sharper. Strong color perception at 20 Â ° but weak at 40 Â °. 30 ° is thus taken as a dividing line between adequate and poor color perception. In dark visibility-adaptation, the light sensitivity is related to the stem density, which reaches only 18 °. From 18 ° to center, the stem density decreases rapidly. From 18 Â ° away from the center, the stem density decreases more gradually, in curves with different inflection points resulting in two humps. The outer edge of the second hump is about 30 Â °, and corresponds to the outside edge of good night vision.
Outside boundary
The outer periphery of edge vision corresponds to the overall visual field boundary. For a single eye, the area of ​​the visual plane can be determined in four angles, each measured from the point of fixation, ie the point at which one's view is directed. These angles, which represent the four directions of the wind, are 60 ° superior (top), 60 ° nasal (towards the nose), 70-75 ° inferior (down), and 100-110 ° temporal (distant from nose and headed to the temple). For both eyes the combined visual field is 130-135 Â ° vertical and 200-220 Â ° horizontal.
Video Peripheral vision
Characteristics
The loss of peripheral vision while maintaining central vision is known as tunnel vision, and loss of central vision while maintaining peripheral vision is known as central scotoma.
The edge visions are weak in humans, especially on differentiating details, colors, and shapes. This is because the receptor cell density and the ganglion in the retina are larger at the center and the lowest at the edges, and, moreover, the representation in the visual cortex is much smaller than the fovea (see visual system for an explanation of these concepts). The distribution of receptor cells in the retina differs between the two main types, stem cells and cone cells. The stem cells can not distinguish color and peak in density near the periphery (at 18 Â ° eccentricity), while the highest cone cell density at the center, fovea, and from there decreases rapidly (by inverted linear function).
The flicker smelting threshold decreases toward the edges, but does so at a lower rate than other visual functions; so the peripheral has a relative advantage to pay attention to flicker. Peripheral vision is also relatively good in motion detection (Magno cell feature).
Central vision is relatively weak in the dark (scotopic vision) because cone cells lack sensitivity at low light levels. The stem cells, which are concentrated farther away from the fovea, operate better than cone cells in low light. This makes edge viewing useful for detecting low-light sources at night (such as dim stars). Therefore, pilots are taught to use peripheral vision to scan planes at night.
The difference between foveal (sometimes also called central) and peripheral vision is reflected in subtle physiological and anatomical differences in the visual cortex. Different visual areas contribute to the processing of visual information coming from different parts of the visual field, and the complex visual area located along the edge of the interhemispheric gap (the deep groove that separates the two hemispheres of the brain) has been associated with peripheral vision. It has been suggested that this area is important for rapid reaction to visual stimuli at the periphery, and monitoring the position of the body relative to gravity.
Peripheral vision can be practiced; For example, magicians who regularly search and capture objects in their peripheral vision have improved capabilities. Jugglers focus on the point specified in the air, so almost all the information required for successful catch is felt in the near-peripheral region.
Maps Peripheral vision
Function
The main functions of peripheral vision are:
- the introduction of famous structures and shapes without the need to focus with the foveal line of sight,
- identification of similar forms and movements (Gestalt psychological law),
- the delivery of sensations that form the background of detailed visual perception.
Extreme edge view
When viewed at a large angle, the iris and pupil appear to be rotated toward the viewer due to optical refraction in the cornea. As a result, the pupil may still be visible at an angle greater than 90 °.
The rich-cone scope of the retina
The retinal edges contain a large conical cone concentration. The retina extends furthest in the superior-nasal 45 Â ° quadrant (in the direction from the pupil to the bridge of the nose) to the greatest extent of the visual plane in the opposite direction, the inferior 45 Â ° basal quadrant (from the pupil of either eye to the bottom of the nearest ear). Vision in the extreme parts of the visual field is thought to be possibly related to threat detection, measuring optical flow, color firmness, or circadian rhythms.
See also
References
Source of the article : Wikipedia
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