Peripheral vision, or indirect vision, is vision as it occurs outside the point of fixation, i.e. away form the center of gaze. The vast majority of the area in the visual field is included in the notion of peripheral vision. "Far peripheral" vision refers to the area at the edges of the visual field, "mid-peripheral" vision refers to medium eccentricities, and "near-peripheral", sometimes referred to as "para-central" vision, exists adjacent to the center of gaze..
The inner boundaries of peripheral vision can be defined in any of several ways depending on the context. In everyday language the term "peripheral vision" is often used to refer to what in technical usage would be called "far peripheral vision." This is vision outside of the range of stereoscopic vision. It can be conceived as bounded at the center by a circle 60° in radius or 120° in diameter, centered around the fixation point, i.e., the point at which one's gaze is directed. However, in common usage, peripheral vision may also refer to the area outside a circle 30° in radius or 60° in diameter. In vision-related fields such as physiology, ophthalmology, optometry, or vision science in general, the inner boundaries of peripheral vision are defined more narrowly in terms of one of several anatomical regions of the central retina, in particular the fovea and the macula.
The fovea is a cone-shaped depression in the central retina measuring 1.5 mm in diameter, corresponding to 5° of the visual field. The outer boundaries of the fovea are visible under a microscope, or with microscopic imaging technology such as OCT or microscopic MRI. When viewed through the pupil, as in an eye exam (using an ophthalmoscope or retinal photography), only the central portion of the fovea may be visible. Anatomists refer to this as the clinical fovea, and say that it corresponds to the anatomical foveola, a structure with a diameter of 0.35 mm corresponding to 1 degree of the visual field. In clinical usage the central part of the fovea is typically referred to simply as the fovea.
In terms of visual acuity, "foveal vision" may be defined as vision using the part of the retina in which a visual acuity of at least 20/20 (6/6 metric or 0.0 LogMAR; internationally 1.0) is attained. This corresponds to using the foveal avascular zone (FAZ) with a diameter of 0.5 mm representing 1.5° of the visual field. Although often idealized as perfect circles, the central structures of the retina tend to be irregular ovals. Thus, foveal vision may also be defined as the central 1.5–2° of the visual field. Vision within the fovea is generally called central vision, while vision outside of the fovea, or even outside the foveola, is called peripheral, or indirect vision.
A ring-shaped region surrounding the fovea, known as the parafovea, is sometimes taken to represent an intermediate form of vision called paracentral vision. The parafovea has an outer diameter of 2.5 mm representing 8° of the visual field. The macula, the next larger region of the retina, is defined as having at least two layers of ganglia (bundles of nerves and neurons) and is sometimes taken as defining the boundaries of central vs. peripheral vision (but this is controversial). The macula has a diameter of 5.5 mm, corresponding to 17° of the visual field. The term is familiar in the general public through the widespread macular degeneration (AMD) at older age, where central vision is lost. When viewed from the pupil, as in an eye exam, only the central portion of the macula may be visible. Known to anatomists as the clinical macula (and in clinical setting as simply the macula) this inner region is thought to correspond to the anatomical fovea.
The dividing line between near and mid peripheral vision at 30° radius is based on several features of visual performance. Visual acuity declines by about 50% every 2.5° from the center up to 30°, at which point visual acuity declines more steeply. Color perception is strong at 20° but weak at 40°. 30° is thus taken as the dividing line between adequate and poor color perception. In dark-adapted vision, light sensitivity corresponds to rod density, which peaks just at 18°. From 18° towards the center, rod density declines rapidly. From 18° away from the center, rod density declines more gradually, in a curve with distinct inflection points resulting in two humps. The outer edge of the second hump is at about 30°, and corresponds to the outer edge of good night vision.
The outer boundaries of peripheral vision correspond to the boundaries of the visual field as a whole. For a single eye, the extent of the visual field can be (roughly) defined in terms of four angles, each measured from the fixation point, i.e., the point at which one's gaze is directed. These angles, representing four cardinal directions, are 60° upwards, 60° nasally (towards the nose), 70–75° downwards, and 100–110° temporally (away from the nose and towards the temple). For both eyes the combined visual field is 130–135° vertically and 200–220° horizontally.
Peripheral vision is weak in humans, especially at distinguishing detail, color, and shape. This is because the density of receptor and ganglion cells in the retina is greater at the center and lowest at the edges, and, moreover, the representation in the visual cortex is much smaller than that of the fovea (see visual system for an explanation of these concepts). The distribution of receptor cells across the retina is different between the two main types, rod cells and cone cells. Rod cells are unable to distinguish color and peak in density in the near periphery (at 18° eccentricity), while cone cell density is highest in the very center, the fovea, and from there declines rapidly (by an inverse linear function).
Flicker fusion thresholds decline towards the periphery, but do that at a lower rate than other visual functions; so the periphery has a relative advantage at noticing flicker. Peripheral vision is also relatively good at detecting motion (a feature of Magno cells).
Central vision is relatively weak in the dark (scotopic vision) since cone cells lack sensitivity at low light levels. Rod cells, which are concentrated further away from the fovea, operate better than cone cells in low light. This makes peripheral vision useful for detecting faint light sources at night (like faint stars). Because of this, pilots are taught to use peripheral vision to scan for aircraft at night.
The distinctions between foveal (sometimes also called central) and peripheral vision are 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 a complex of visual areas located along the banks of the interhemispheric fissure (a deep groove that separates the two brain hemispheres) has been linked to peripheral vision. It has been suggested that these areas are important for fast reactions to visual stimuli in the periphery, and monitoring body position relative to gravity.
The main functions of peripheral vision are:
When viewed at large angles, the iris and pupil appear to be rotated toward the viewer due to the optical refraction in the cornea. As a result, the pupil may still be visible at angles greater than 90°.
The rim of the retina contains a large concentration of cone cells. The retina extends farthest in the superior-nasal 45° quadrant (in the direction from the pupil to the bridge of the nose) with the greatest extent of the visual field in the opposite direction, the inferior temporal 45° quadrant (from the pupil of either eye towards the bottom of the nearest ear). Vision at this extreme part of the visual field is thought to be possibly concerned with threat detection, measuring optical flow, color constancy, or circadian rhythm.
With our head and eyes steady, our normal binocular vision covers a visual field of about 200 to 220 degrees of visual angle.
The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation.Foveal
The foveal system of the human eye is the only part of the retina that permits 100% visual acuity. The line of sight is a virtual line connecting the fovea with a fixation point in the outside world.
The discovery of the line-of-sight is attributed to Leonardo da Vinci.His main experimental finding was that there is a distinct and clear vision only at the line-of-sight, the optical line that ends at the fovea. Although he did not use these words literally, he actually is the father of the modern distinction between foveal vision (a more precise term for central vision) and peripheral vision.
Leonardo da Vinci, (1452–1519) was the first person known in Europe to recognize the special optical qualities of the eye. He derived his insights partly through introspection but mainly through a process that could be described as optical modelling. Based on dissection of the human eye he made experiments with water-filled crystal balls. He wrote "The function of the human eye, ... was described by a large number of authors in a certain way. But I found it to be completely different."
The modern diagram to the right shows that the fovea is a sort of pit. The Latin word fovea means pitfall.Foveated rendering
Foveated rendering is an upcoming graphics-rendering technique which uses an eye tracker integrated with a virtual reality headset to reduce the rendering workload by greatly reducing the image quality in the peripheral vision (outside of the zone gazed by the fovea).Greyout
A greyout (US English grayout) is a transient loss of vision characterized by a perceived dimming of light and color, sometimes accompanied by a loss of peripheral vision. It is a precursor to fainting or a blackout and is caused by hypoxia (low brain oxygen level), often due to a loss of blood pressure.
Greyouts have a variety of possible causes:
Shock, such as hypovolemia, even in mild form such as when drawing blood.
Suddenly standing up (see orthostatic hypotension), especially if sick, hungover, or suffering from low blood pressure.
Paradoxically, hyperventilation: self-induced hypocapnia such as in the fainting game or in shallow water blackout.
Panic attackUsually recovery is rapid and a greyout can be readily reversed by lying down. This way, the cardiovascular system does not need to work against gravity for blood to reach the brain.
A greyout may be experienced by aircraft pilots pulling high positive g-forces as when pulling up into a loop or a tight turn forcing blood to the lower extremities of the body and lowering blood pressure in the brain. This is the reverse of a redout, or a reddening of the vision, which is the result of negative g-forces caused by performing an outside loop, that is by pushing the nose of the aircraft down. Redouts are potentially dangerous and can cause retinal damage and hemorrhagic stroke. Pilots of high performance aircraft can increase their resistance to greyout by using a g-suit, which controls the pooling of blood in the lower limbs, but there is no suit yet capable of controlling a redout. In both cases symptoms may be remedied immediately by easing pressure on the flight controls. Continued, or heavy g-force will rapidly progress to g-LOC (g-force induced Loss of Consciousness).
Surprisingly, even during a heavy greyout, where the visual system is severely impaired, pilots can still hear, feel, and speak. Complete greyout and loss of consciousness are separate events.
Another common occurrence of greyouts is in roller coaster riders. Many roller coasters put riders through positive g-forces, particularly in vertical loops and helices. Roller coasters rarely have high enough negative g-forces to induce redouts, as most low-g elements are designed to simulate weightlessness.NGC 7
NGC 7 is a spiral galaxy located in the Sculptor constellation. It was discovered by English astronomer John Herschel in 1834, who was using an 18.7 inch reflector telescope at the time. Astronomer Steve Gottlieb described the galaxy as faint, albeit large, and edge-on from the perspective of the Milky Way; he also noted how the galaxy could only be observed clearly with the peripheral vision, not by looking directly at it.Peripheral Vision (album)
Peripheral Vision is the second studio album by American rock band Turnover. Produced by Will Yip, the album was released on May 4, 2015 through Run for Cover Records. Following the release of their debut album Magnolia (2013), Turnover parted ways with original guitarist Kyle Kojan, replacing him with Eric Soucy. For Peripheral Vision, Turnover returned to producer Will Yip, who shares songwriting credits on the entire album. It was recorded at his studio, Studio 4, in Conshohocken, Pennsylvania.
The album finds the band shifting from their pop punk origins to a more atmospheric, dream pop-type sound. Peripheral Vision peaked on at number four on Billboard's Heatseekers Albums chart, and critical reviews were largely positive, focusing on its stylistic progression.Peripheral vision horizon display
The peripheral vision horizon display, also called PVHD or the Malcolm Horizon (after inventor Dr. Richard Malcolm), is an aircraft cockpit instrument which assists pilots in maintaining proper attitude.
The PVHD was developed in the mid-1970s and manufactured in the early 1980s as a cockpit instrument to assist the pilot with being better aware of the aircraft attitude at all times. The development of the PVHD was driven by a high incidence of military aircraft accidents due to "attitude awareness issues." The PVHD was noted to have a subliminal effect on the pilot because in actual use the display was set so dim that it could barely be seen.
The PVHD was well received by pilots that tested it in helicopters as well as fixed-wing aircraft. It was flown in F-4s and A-10s, as well as helicopters. Initial production in 1983, however, was for the SR-71 Blackbird as an aid when refueling in the air.The initial concept demonstration was done in Canadian military laboratories and later development was undertaken by Varian Canada in Georgetown, Ontario. In 1981, Varian sold the project to Garrett Manufacturing in Rexdale, Toronto, Ontario.Periphery
Periphery or Peripheral may refer to:
Periphery (band), American progressive metal band
Periphery (album), released in 2010 by Periphery
Periphery, a group of political entities in BattleTech, a wargaming franchise
Periphery countries, the least developed countries in world systems theory
Periphery (France), statistical area designating a commuter belt around an urban unit
Peripheries of Greece or administrative regions of Greece (Greek: περιφέρειες, peripheries), the country's first-level administrative divisions
Peripheral units of Greece or regional units of Greece (Greek: περιφερειακές ενότητες, perifereiakés enóti̱tes), second-level administrative divisions
Periphery, all of the body outside of the central nervous system
Peripherally selective drug, a drug with a primary mechanism of action outside of the central nervous system
Peripheral nervous system, the part of the nervous system outside of the central nervous system
Peripheral, an external device attached to a computer
The Peripheral, a 2014 novel by William Gibson
Peripheral, an alternate mathematical term for boundary parallel in manifold theory,
Peripheral cycle, a mathematical term in graph theory
Peripheral vision, a part of vision that occurs on the edges of the field of visionRetinitis pigmentosa
Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreased peripheral vision (side vision). Onset of symptoms is generally gradual. As peripheral vision worsens, people may experience "tunnel vision". Complete blindness is uncommon.Retinitis pigmentosa is generally inherited from a person's parents. Mutations in one of more than 50 genes is involved. The underlying mechanism involves the progressive loss of rod photoreceptor cells in the back of the eye. This is generally followed by loss of cone photoreceptor cells. Diagnosis is by an examination of the retina finding dark pigment deposits. Other supportive testing may include an electroretinogram, visual field testing, or genetic testing.There is currently no cure for retinitis pigmentosa. Efforts to manage the problem may include the use of low vision aids, portable lighting, or a guide dog. Vitamin A palmitate supplements may be useful to slow worsening. A visual prosthesis may be an option in certain people with severe disease. It is estimated to affect 1 in 4,000 people. Onset is often in childhood but some are not affected until adulthood.Rod cell
Rod cells are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor, cone cells. Rods are usually found concentrated at the outer edges of the retina and are used in peripheral vision. On average, there are approximately 92 million rod cells in the human retina. Rod cells are more sensitive than cone cells and are almost entirely responsible for night vision. However, rods have little role in color vision, which is the main reason why colors are much less apparent in dim light, and not at all at night.School bus yellow
School bus yellow is a color that was specifically formulated for use on school buses in North America in 1939. The color is now officially known in Canada and the U.S. as National School Bus Glossy Yellow and was originally called National School Bus Chrome. The pigment used for this color was, for a long time, the lead-containing chrome yellow.The color was chosen because it attracts attention and is noticed quickly in peripheral vision, faster than any other color. Scientists describe this as follows: "Lateral peripheral vision for detecting yellows is 1.24 times greater than for red."In April 1939, Dr. Frank W. Cyr, a professor at Teachers College, Columbia University in New York organized a conference that established national school-bus construction standards for the U.S., including the standard color of yellow for the school bus. It became known officially as "National School Bus Chrome". The color was selected because black lettering on that hue was easiest to see in the semi-darkness of early morning.
The conference met for seven days and the attendees created a total of 44 standards, including specifications regarding body length, ceiling height and aisle width. Paint experts from DuPont and Pittsburgh Paints participated. Dr. Cyr's conference, funded by a $5,000 grant from the Rockefeller Foundation, was also a landmark event in as much as it included transportation officials from each of the then-48 states, as well as specialists from school bus manufacturing and paint companies. The color was adopted by the National Bureau of Standards (now the National Institute of Standards and Technology) as Federal Standard No. 595a, Color 13432.
The conference approach to school bus safety, as well as the yellow color, have endured into the 21st century. Dr. Cyr became known as the "Father of the Yellow School Bus."Stereoblindness
Stereoblindness (also stereo blindness) is the inability to see in 3D using stereopsis, or stereo vision, resulting in an inability to perceive stereoscopic depth by combining and comparing images from the two eyes.
Individuals with only one functioning eye always have this condition; the condition also results when two eyes do not function together properly.
Most stereoblind persons with two healthy eyes do employ binocular vision to some extent, albeit less than persons with normally developed eyesight. This was shown in a study in which stereoblind subjects were posed with the task of judging the direction of rotation of a simulated transparent cylinder: the subjects performed better when using two eyes than when using their preferred eye. They appeared to judge the direction of rotation from the images in each eye separately and then to combine these judgments, rather than relying on differences between the images in the two eyes. Also, purely binocular motion stimuli appear to influence stereoblind persons' sensation of self-motion. Furthermore, in some cases each eye can contribute to peripheral vision for one side of the field of view (see also monofixation syndrome).
However, there is an exception to this: those with a true congenital alternating squint. Those with true congenital alternating squints have two healthy eyes, and the ability to switch (by choice) between seeing with either eye. However, stereoscopic and three dimensional vision can never be achieved in this condition (attempts to train those with true congenital alternating squints into binocular vision results in double vision, which can be irreversible).This Is Cinerama
This is Cinerama is a 1952 full-length film directed by Merian C. Cooper and starring Lowell Thomas. It is designed to introduce the widescreen process Cinerama, which broadens the aspect ratio so the viewer's peripheral vision is involved. This is Cinerama premiered on September 30, 1952 at the Broadway Theatre, in New York City.Tunnel vision
Tunnel vision is the loss of peripheral vision with retention of central vision, resulting in a constricted circular tunnel-like field of vision.Tunnel vision (disambiguation)
Tunnel vision is the loss of peripheral vision
Tunnel vision or Tunnel Vision may also refer to:
Tunnel vision (metaphor), the reluctance to consider alternatives to one's preferred line of thought
Tunnel vision (marksmanship), when a shooter is focused on a target, and thus misses what goes on around that targetTurnover (band)
Turnover is an American rock band from Virginia Beach, Virginia. Formed in 2009, the band is signed with the Run for Cover Records label. Turnover has released three albums, two EPs and a handful of singles.Vernier acuity
Vernier acuity is a type of visual acuity – more precisely of hyperacuity – that measures the ability to discern a disalignment among two line segments or gratings. A subject's vernier (IPA: /ˈvɜːrniər/ or /ˈvɜːniə/) acuity is the smallest visible offset between the stimuli that can be detected. Because the disalignments are often much smaller than the diameter and spacing of retinal receptors, vernier acuity requires neural processing and "pooling" to detect it. Because vernier acuity exceeds acuity by far, the phenomenon has been termed hyperacuity. Vernier acuity develops rapidly during infancy and continues to slowly develop throughout childhood. At approximately three to twelve months old, it surpasses grating acuity in foveal vision in humans. However, vernier acuity decreases more quickly than grating acuity in peripheral vision. Vernier acuity was first explained by Ewald Hering in 1899, based on earlier data by Alfred Volkmann in 1863 and results by Ernst Anton Wülfing in 1892.Vernier acuity is resistant to defocus, motion, and luminance, but is subject to practice effects and changes in attention. After training, observers' threshold has been shown to improve as much as 6 fold.Visual field
The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments".The equivalent concept for optical instruments and image sensors is the field of view (FOV).
In optometry, ophthalmology, and neurology, a visual field test is used to determine whether the visual field is affected by diseases that cause local scotoma or a more extensive loss of vision or a reduction in sensitivity (increase in threshold).Visual field test
A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, pituitary disease, brain tumours or other neurological deficits. Visual field testing can be performed clinically by keeping the subject's gaze fixed while presenting objects at various places within their visual field. Simple manual equipment can be used such as in the tangent screen test or the Amsler grid. When dedicated machinery is used it is called a perimeter.
The exam may be performed by a technician in one of several ways. The test may be performed by a technician directly, with the assistance of a machine, or completely by an automated machine. Machine based tests aid diagnostics by allowing a detailed printout of the patient's visual field.
Other names for this test may include perimetry, Tangent screen exam, Automated perimetry exam, Goldmann visual field exam, or the Humphrey field exam.