document_title: Visual acuity

question_text: what is the normal vision of human eye

question_tokens: what is the normal vision of human eye

text: Visual acuity

text: Definition[edit]

text: Visual acuity is a measure of the spatial resolution of the visual processing system. VA, as it is sometimes referred to by optical professionals, is tested by requiring the person whose vision is being tested to identify so-called optotypes – stylized letters, Landolt rings, pediatric symbols, symbols for the illiterate, standardized Cyrillic letters in the Golovin–Sivtsev table, or other patterns – on a printed chart (or some other means) from a set viewing distance. Optotypes are represented as black symbols against a white background (i.e. at maximum contrast). The distance between the person's eyes and the testing chart is set so as to approximate "optical infinity" in the way the lens attempts to focus (far acuity), or at a defined reading distance (near acuity).

text: A reference value above which visual acuity is considered normal is called 6/6 vision, the USC equivalent of which is 20/20 vision: At 6 meters or 20 feet, a human eye with that performance is able to separate contours that are approximately 1.75 mm apart.[4] Vision of 6/12 corresponds to lower, vision of 6/3 to better performance. Normal individuals have an acuity of 6/4 or better (depending on age and other factors).

text: In the expression 6/x vision, the numerator (6) is the distance in meters between the subject and the chart and the denominator (x) the distance at which a person with 6/6 acuity would discern the same optotype. Thus, 6/12 means that a person with 6/6 vision would discern the same optotype from 12 meters away (i.e. at twice the distance). This is equivalent to saying that with 6/12 vision, the person possesses half the spatial resolution and needs twice the size to discern the optotype.

text: A simple and efficient way to state acuity is by solving the fraction to a decimal number. 6/6 then corresponds to an acuity (or a Visus) of 1.0 (see Expression below). 6/3 corresponds to 2.0, which is often attained by well-corrected healthy young subjects with binocular vision. Stating acuity as a decimal number is the standard in European countries, as required by the European norm (EN ISO 8596, previously DIN 58220).

text: The precise distance at which acuity is measured is not important as long as it is sufficiently far away and the size of the optotype on the retina is the same. That size is specified as a visual angle, which is the angle, at the eye, under which the optotype appears. For 6/6 = 1.0 acuity, the size of a letter on the Snellen chart or Landolt C chart is a visual angle of 5 arc minutes (1 arc min = 1/60 of a degree). By the design of a typical optotype (like a Snellen E or a Landolt C), the critical gap that needs to be resolved is 1/5 this value, i.e., 1 arc min. The latter is the value used in the international definition of visual acuity:

text: Acuity = 1/gap size [arc min]

text: Acuity is a measure of visual performance and does not relate to the eyeglass prescription required to correct vision. Instead, an eye exam seeks to find the prescription that will provide the best corrected visual performance achievable. The resulting acuity may be greater or less than 6/6 = 1.0. Indeed, a subject diagnosed as having 6/6 vision will often actually have higher visual acuity because, once this standard is attained, the subject is considered to have normal (in the sense of undisturbed) vision and smaller optotypes are not tested. Emmetropic subjects with 6/6 vision or "better" (20/15, 20/10, etc.), may still benefit from an eyeglass correction for other problems related to the visual system, such as astigmatism, ocular injuries, or presbyopia.

text: Measurement[edit]

text: Visual acuity is measured by a psychophysical procedure and as such relates the physical characteristics of a stimulus to a subject's percept and his/her resulting responses. Measurement can be by using an eye chart invented by Ferdinand Monoyer, by optical instruments, or by computerized tests[5] like the FrACT.[6]

text: Care must be taken that viewing conditions correspond to the standard,[7] such as correct illumination of the room and the eye chart, correct viewing distance, enough time for responding, error allowance, and so forth. In European countries, these conditions are standardized by the European norm (EN ISO 8596, previously DIN 58220).

text: History[edit]

text:
Year
Event

1843
Vision test types are invented in 1843 by the German ophthalmologist Heinrich Kuechler (1811–1873), in Darmstadt, Germany. He argues for need to standardize vision tests and produces three reading charts to avoid memorization.

1854
Eduard Jäger von Jaxtthal, a Vienna oculist, makes improvements to eye chart test types that were developed by Heinrich Kuechler. He publishes, in German, French, English and other languages, a set of reading samples to document functional vision. He uses fonts that were available in the State Printing House in Vienna in 1854 and labels them with the numbers from that printing house catalogue, currently known as Jaeger numbers.

1862
Herman Snellen, a Dutch ophthalmologist, publishes in Utrecht his "Optotypi ad visum determinandum" ("Probebuchstaben zur Bestimmung der Sehschärfe"), the first visual chart based on "Optotypes", advocating the need for standardized vision tests. Snellen's Optotypes are not identical to the test letters used today. They were printed in an 'Egyptian Paragon' font (i.e. using serifs).[8][9]

1888
Edmund Landolt introduces the broken ring, now known as the Landolt ring, which later becomes an international standard.[10][11]

1894

Theodor Wertheim in Berlin presents detailed measurements of acuity in peripheral vision.[2][12]

1978

Hugh Taylor uses these design principles for a "Tumbling E Chart" for illiterates, later used[13] to study the visual acuity of Australian Aborigines.[9]

1982

Rick Ferris et al. of the National Eye Institute chooses the LogMAR chart layout, implemented with Sloan letters, to establish a standardized method of visual acuity measurement for the Early Treatment of Diabetic Retinopathy Study (ETDRS). These charts are used in all subsequent clinical studies, and did much to familiarize the profession with the new layout and progression. Data from the ETDRS were used to select letter combinations that give each line the same average difficulty, without using all letters on each line.

1984

The International Council of Ophthalmology approves a new 'Visual Acuity Measurement Standard', also incorporating the above features.

1988

Antonio Medina and Bradford Howland of the Massachusetts Institute of Technology develop a novel eye testing chart using letters that become invisible with decreasing acuity, rather than blurred as in standard charts. They demonstrate the arbitrary nature of the Snellen fraction and warn about the accuracy of visual acuity determined by using charts of different letter types, calibrated by Snellen's system.[14]

text: Physiology[edit]

text: Daylight vision (i.e. photopic vision) is subserved by cone receptor cells which have high spatial density (in the central fovea) and allow high acuity of 6/6 or better. In low light (i.e., scotopic) vision, cones do not have sufficient sensitivity and vision is subserved by rods. Spatial resolution is then much lower. This is due to spatial summation of rods, i.e. a number of rods merge into a bipolar cell, in turn connecting to a ganglion cell, and the resulting unit for resolution is large, and acuity small. Note that there are no rods in the very center of the visual field (the foveola), and highest performance in low light is achieved in near peripheral vision[2]

text: The maximum angular resolution of the human eye at a distance of 1 km is typically 30 to 60 cm. This gives an angular resolution of between 0.02 and 0.03 degrees, which is roughly 1.2–1.8 arc minutes per line pair, which implies a pixel spacing of 0.6–0.9 arc minutes.[15][16] 6/6 vision is defined as the ability to resolve two points of light separated by a visual angle of one minute of arc, or about 320–386 pixels per inch for a display on a device held 25 to 30 cm from the eye.[17]

text: Thus, visual acuity, or resolving power (in daylight, central vision), is the property of cones.[18] To resolve detail, the eye's optical system has to project a focused image on the fovea, a region inside the macula having the highest density of cone photoreceptor cells (the only kind of photoreceptors existing in the fovea's very center of 300 μm diameter), thus having the highest resolution and best color vision. Acuity and color vision, despite being mediated by the same cells, are different physiologic functions that do not interrelate except by position. Acuity and color vision can be affected independently.

text: The grain of a photographic mosaic has just as limited resolving power as the "grain" of the retinal mosaic. In order to see detail, two sets of receptors must be intervened by a middle set. The maximum resolution is that 30 seconds of arc, corresponding to the foveal cone diameter or the angle subtended at the nodal point of the eye. In order to get reception from each cone, as it would be if vision was on a mosaic basis, the "local sign" must be obtained from a single cone via a chain of one bipolar, ganglion, and lateral geniculate cell each. A key factor of obtaining detailed vision, however, is inhibition. This is mediated by neurons such as the amacrine and horizontal cells, which functionally render the spread or convergence of signals inactive. This tendency to one-to-one shuttle of signals is powered by brightening of the center and its surroundings, which triggers the inhibition leading to a one-to-one wiring. This scenario, however, is rare, as cones may connect to both midget and flat (diffuse) bipolars, and amacrine and horizontal cells can merge messages just as easily as inhibit them.[4]

text: Light travels from the fixation object to the fovea through an imaginary path called the visual axis. The eye's tissues and structures that are in the visual axis (and also the tissues adjacent to it) affect the quality of the image. These structures are: tear film, cornea, anterior chamber, pupil, lens, vitreous, and finally the retina. The posterior part of the retina, called the retinal pigment epithelium (RPE) is responsible for, among many other things, absorbing light that crosses the retina so it cannot bounce to other parts of the retina. Interestingly, in many vertebrates, such as cats, where high visual acuity is not a priority, there is a reflecting tapetum layer that gives the photoreceptors a "second chance" to absorb the light, thus improving the ability to see in the dark. This is what causes an animal's eyes to seemingly glow in the dark when a light is shone on them. The RPE also has a vital function of recycling the chemicals used by the rods and cones in photon detection. If the RPE is damaged and does not clean up this "shed" blindness can result.

text: As in a photographic lens, visual acuity is affected by the size of the pupil. Optical aberrations of the eye that decrease visual acuity are at a maximum when the pupil is largest (about 8 mm), which occurs in low-light conditions. When the pupil is small (1–2 mm), image sharpness may be limited by diffraction of light by the pupil (see diffraction limit). Between these extremes is the pupil diameter that is generally best for visual acuity in normal, healthy eyes; this tends to be around 3 or 4 mm.

text: If the optics of the eye were otherwise perfect, theoretically, acuity would be limited by pupil diffraction, which would be a diffraction-limited acuity of 0.4 minutes of arc (minarc) or 6/2.6 acuity. The smallest cone cells in the fovea have sizes corresponding to 0.4 minarc of the visual field, which also places a lower limit on acuity. The optimal acuity of 0.4 minarc or 6/2.6 can be demonstrated using a laser interferometer that bypasses any defects in the eye's optics and projects a pattern of dark and light bands directly on the retina. Laser interferometers are now used routinely in patients with optical problems, such as cataracts, to assess the health of the retina before subjecting them to surgery.

text: The visual cortex is the part of the cerebral cortex in the posterior part of the brain responsible for processing visual stimuli, called the occipital lobe. The central 10° of field (approximately the extension of the macula) is represented by at least 60% of the visual cortex. Many of these neurons are believed to be involved directly in visual acuity processing.

text: Proper development of normal visual acuity depends on a human or an animal having normal visual input when it is very young. Any visual deprivation, that is, anything interfering with such input over a prolonged period of time, such as a cataract, severe eye turn or strabismus, anisometropia (unequal refractive error between the two eyes), or covering or patching the eye during medical treatment, will usually result in a severe and permanent decrease in visual acuity and pattern recognition in the affected eye if not treated early in life, a condition known as amblyopia. The decreased acuity is reflected in various abnormalities in cell properties in the visual cortex. These changes include a marked decrease in the number of cells connected to the affected eye as well as cells connected to both eyes in cortical area V1, resulting in a loss of stereopsis, i.e. depth perception by binocular vision (colloquially: "3D vision"). The period of time over which an animal is highly sensitive to such visual deprivation is referred to as the critical period.

text: The eye is connected to the visual cortex by the optic nerve coming out of the back of the eye. The two optic nerves come together behind the eyes at the optic chiasm, where about half of the fibers from each eye cross over to the opposite side and join fibers from the other eye representing the corresponding visual field, the combined nerve fibers from both eyes forming the optic tract. This ultimately forms the physiological basis of binocular vision. The tracts project to a relay station in the midbrain called the lateral geniculate nucleus, part of the thalamus, and then to the visual cortex along a collection of nerve fibers called the optic radiation.

text: Any pathological process in the visual system, even in older humans beyond the critical period, will often cause decreases in visual acuity. Thus measuring visual acuity is a simple test in accessing the health of the eyes, the visual brain, or pathway to the brain. Any relatively sudden decrease in visual acuity is always a cause for concern. Common causes of decreases in visual acuity are cataracts and scarred corneas, which affect the optical path, diseases that affect the retina, such as macular degeneration and diabetes, diseases affecting the optic pathway to the brain such as tumors and multiple sclerosis, and diseases affecting the visual cortex such as tumors and strokes.

text: Though the resolving power depends on the size and packing density of the photoreceptors, the neural system must interpret the receptors’ information. As determined from single-cell experiments on the cat and primate, different ganglion cells in the retina are tuned to different spatial frequencies, so some ganglion cells at each location have better acuity than others. Ultimately, however, it appears that the size of a patch of cortical tissue in visual area V1 that processes a given location in the visual field (a concept known as cortical magnification) is equally important in determining visual acuity. In particular, that size is largest in the fovea’s center, and decreases with increasing distance from there.[2]

text: Optical aspects[edit]

text: Besides the neural connections of the receptors, the optical system is an equally key player in retinal resolution. In the ideal eye, the image of a diffraction grating can subtend 0.5 micrometre on the retina. This is certainly not the case, however, and furthermore the pupil can cause diffraction of the light. Thus, black lines on a grating will be mixed with the intervening white lines to make a gray appearance. Defective optical issues (such as uncorrected myopia) can render it worse, but suitable lenses can help. Images (such as gratings) can be sharpened by lateral inhibition, i.e., more highly excited cells inhibiting the less excited cells. A similar reaction is in the case of chromatic aberrations, in which the color fringes around black-and-white objects are inhibited similarly.[4]

text: Expression[edit]

text:
Visual acuity scales

Foot
Metre
Decimal
LogMAR

20/200
6/60
0.10
1.00

20/160
6/48
0.125
0.90

20/125
6/38
0.16
0.80

20/100
6/30
0.20
0.70

20/80
6/24
0.25
0.60

20/63
6/19
0.32
0.50

20/50
6/15
0.40
0.40

20/40
6/12
0.50
0.30

20/32
6/9.5
0.63
0.20

20/25
6/7.5
0.80
0.10

20/20
6/6.0
1.00
0.00

20/16
6/4.8
1.25
−0.10

20/12.5
6/3.8
1.60
−0.20

20/10
6/3.0
2.00
−0.30

text: Visual acuity is often measured according to the size of letters viewed on a Snellen chart or the size of other symbols, such as Landolt Cs or the E Chart.

text: In some countries, acuity is expressed as a vulgar fraction, and in some as a decimal number.

text: Using the meter as a unit of measurement, (fractional) visual acuity is expressed relative to 6/6. Otherwise, using the foot, visual acuity is expressed relative to 20/20. For all practical purposes, 20/20 vision is equivalent to 6/6. In the decimal system, acuity is defined as the reciprocal value of the size of the gap (measured in arc minutes) of the smallest Landolt C, the orientation of which can be reliably identified. A value of 1.0 is equal to 6/6.

text: LogMAR is another commonly used scale, expressed as the (decadic) logarithm of the minimum angle of resolution (MAR). The LogMAR scale converts the geometric sequence of a traditional chart to a linear scale. It measures visual acuity loss: positive values indicate vision loss, while negative values denote normal or better visual acuity. This scale is rarely used clinically; it is more frequently used in statistical calculations because it provides a more scientific equivalent for the traditional clinical statement of “lines lost” or “lines gained”, which is valid only when all steps between lines are equal, which is not usually the case.

text: A visual acuity of 6/6 is frequently described as meaning that a person can see detail from 6 metres (20 ft) away the same as a person with "normal" eyesight would see from 6 metres. If a person has a visual acuity of 6/12, he is said to see detail from 6 metres (20 ft) away the same as a person with "normal" eyesight would see it from 12 metres (39 ft) away.

text: Healthy young observers may have a binocular acuity superior to 6/6; the limit of acuity in the unaided human eye is around 6/3–6/2.4 (20/10–20/8), although 6/3 was the highest score recorded in a study of some US professional athletes.[20] Some birds of prey, such as hawks, are believed to have an acuity of around 20/2;[21] in this respect, their vision is much better than human eyesight.

text: When visual acuity is below the largest optotype on the chart, the reading distance is reduced until the patient can read it. Once the patient is able to read the chart, the letter size and test distance are noted. If the patient is unable to read the chart at any distance, he or she is tested as follows:

text:
Name
Abbreviation
Definition

Counting Fingers
CF
Ability to count fingers at a given distance. This test method is only utilized after it has been determined that the patient is not able to make out any of the letters, rings, or images on the acuity chart. The letters CF, and the testing distance, would represent the patient's acuity.
For example, the recording CF 5' would mean the patient was able to count the examiner's fingers from a maximum distance of 5 feet directly in front of the examiner.
(The results of this test, on the same patient, may vary from examiner to examiner. This is due more so to the size differences of the various examiner's hands and fingers, than fluctuating vision.)

Hand Motion
HM
Ability to distinguish whether or not there is movement of the examiner's hand directly in front of the patient's eyes. This test method is only utilized after a patient shows little or no success with the Counting Fingers test. The letters HM, and the testing distance, would represent the patient's acuity.
For example, the recording HM 2' would mean that the patient was able to distinguish movement of the examiner's hand from a maximum distance of 2 feet directly in front of the examiner.
(The results of the Hand Motion test are often recorded without the testing distance. This is due to the fact that this test is performed after the patient cannot "pass" the Counting Fingers test. At this point, the examiner is usually directly in front of the patient, and it is assumed that the Hand Motion test is performed at a testing distance of 1 foot or less.)

Light Perception
LP
Ability to perceive any light. This test method is utilized only after a patient shows little or no success with the Hand Motion test. In this test, an examiner shines a pen light at the patient's pupil and asks the patient to either, point to the light source, or, describe the direction that the light is coming from (up, out, straight ahead, down and out, etc.). If the patient is able to perceive light, the letters LP are recorded to represent the patient's acuity. If the patient is unable to perceive any light, the letters NLP (No Light Perception) are recorded. A patient with no light perception in one eye is considered blind in the respective eye. If NLP is recorded in both eyes, the patient is described as having total blindness.

text: Legal definitions[edit]

text: Various countries have defined statutory limits for poor visual acuity that qualifies as a disability. For example, in Australia, the Social Security Act defines blindness as:

text: A person meets the criteria for permanent blindness under section 95 of the Social Security Act if the corrected visual acuity is less than 6/60 on the Snellen Scale in both eyes or there is a combination of visual defects resulting in the same degree of permanent visual loss.

text: In the USA, the relevant federal statute defines blindness as follows:[22]

text: [T]he term "blindness" means central visual acuity of 20/200 or less in the better eye with the use of a correcting lens. An eye that is accompanied by a limitation in the fields of vision such that the widest diameter of the visual field subtends an angle no greater than 20 degrees shall be considered for purposes in this paragraph as having a central visual acuity of 20/200 or less.

text: A person's visual acuity is registered documenting the following: whether the test was for distant or near vision, the eye(s) evaluated and whether corrective lenses (i.e. glasses or contact lenses) were used:

text:
Distance from the chart

D (distant) for the evaluation done at 20 feet (6.1 m).
N (near) for the evaluation done at 15.7 inches (40 cm).

Eye evaluated

OD (Latin oculus dexter) for the right eye.
OS (Latin oculus sinister) for the left eye.
OU (Latin oculi uterque) for both eyes.

Usage of spectacles during the test

cc (Latin cum correctore) with correctors.
sc: (Latin sine correctore) without correctors.

Pinhole occluder

The abbreviation PH is followed by the visual acuity as measured with a pinhole occluder, which temporarily corrects for refractive errors such as myopia or astigmatism.

text: So, distant visual acuity of 6/10 and 6/8 with pinhole in the right eye will be: DscOD 6/20 PH 6/8. Distant visual acuity of count fingers and 6/17 with pinhole in the left eye will be: DscOS CF PH 16/17. Near visual acuity of 6/8 with pinhole remaining at 6/8 in both eyes with spectacles will be: NccOU 6/8 PH 6/8.

text: "Dynamic visual acuity" defines the ability of the eye to visually discern fine detail in a moving object.

text: Measurement considerations[edit]

text: Visual acuity measurement involves more than being able to see the optotypes. The patient should be cooperative, understand the optotypes, be able to communicate with the physician, and many more factors. If any of these factors is missing, then the measurement will not represent the patient's real visual acuity.

text: Visual acuity is a subjective test meaning that if the patient is unwilling or unable to cooperate, the test cannot be done. A patient who is sleepy, intoxicated, or has any disease that can alter their consciousness or mental status, may not achieve their maximum possible acuity.

text: Illiterate patients who cannot read letters and/or numbers will be registered as having very low visual acuity if this is not known. Some patients will not tell the examiner that they don't know the optotypes, unless asked directly about it. Brain damage can result in a patient not being able to recognize printed letters, or being unable to spell them.

text: A motor inability can make a person respond incorrectly to the optotype shown and negatively affect the visual acuity measurement.

text: Variables such as pupil size, background adaptation luminance, duration of presentation, type of optotype used, interaction effects from adjacent visual contours (or “crowding") can all affect visual acuity measurement.

text: Testing in children[edit]

text: The newborn’s visual acuity is approximately 6/133, developing to 6/6 well after the age of six months in most children, according to a study published in 2009.[23]

text: The measurement of visual acuity in infants, pre-verbal children and special populations (for instance, handicapped individuals) is not always possible with a letter chart. For these populations, specialised testing is necessary. As a basic examination step, one must check whether visual stimuli can be fixated, centered and followed.

text: More formal testing using preferential looking techniques use Teller acuity cards (presented by a technician from behind a window in the wall) to check whether the child is more visually attentive to a random presentation of vertical or horizontal gratings on one side compared with a blank page on the other side — the bars become progressively finer or closer together, and the endpoint is noted when the child in its adult carer's lap equally prefers the two sides.

text: Another popular technique is electro-physiologic testing using visual evoked (cortical) potentials (VEPs or VECPs), which can be used to estimate visual acuity in doubtful cases and expected severe vision loss cases like Leber's congenital amaurosis.

text: VEP testing of acuity is somewhat similar to preferential looking in using a series of black and white stripes (sine wave gratings) or checkerboard patterns (which produce larger responses than stripes). Behavioral responses are not required and brain waves created by the presentation of the patterns are recorded instead. The patterns become finer and finer until the evoked brain wave just disappears, which is considered to be the endpoint measure of visual acuity. In adults and older, verbal children capable of paying attention and following instructions, the endpoint provided by the VEP corresponds very well to the psychophysical measure in the standard measurement (i.e. the perceptual endpoint determined by asking the subject when they can no longer see the pattern). There is an assumption that this correspondence also applies to much younger children and infants, though this does not necessarily have to be the case. Studies do show the evoked brain waves, as well as derived acuities, are very adult-like by one year of age.

text: For reasons not totally understood, until a child is several years old, visual acuities from behavioral preferential looking techniques typically lag behind those determined using the VEP, a direct physiological measure of early visual processing in the brain. Possibly it takes longer for more complex behavioral and attentional responses, involving brain areas not directly involved in processing vision, to mature. Thus the visual brain may detect the presence of a finer pattern (reflected in the evoked brain wave), but the "behavioral brain" of a small child may not find it salient enough to pay special attention to.

text: A simple but less-used technique is checking oculomotor responses with an optokinetic nystagmus drum, where the subject is placed inside the drum and surrounded by rotating black and white stripes. This creates involuntary abrupt eye movements (nystagmus) as the brain attempts to track the moving stripes. There is a good correspondence between the optokinetic and usual eye-chart acuities in adults. A potentially serious problem with this technique is that the process is reflexive and mediated in the low-level brain stem, not in the visual cortex. Thus someone can have a normal optokinetic response and yet be cortically blind with no conscious visual sensation.

text: "Normal" visual acuity[edit]

text: Visual acuity depends upon how accurately light is focused on the retina, the integrity of the eye's neural elements, and the interpretative faculty of the brain.[24] "Normal" visual acuity (in central, i.e. foveal vision) is frequently considered to be what was defined by Herman Snellen as the ability to recognize an optotype when it subtended 5 minutes of arc, that is Snellen's chart 6/6 meter, 20/20 feet, 1.00 decimal or 0.0 logMAR. In young humans, the average visual acuity of a healthy, emmetropic eye (or ametropic eye with correction) is approximately 6/5 to 6/4, so it is inaccurate to refer to 6/6 visual acuity as "perfect" vision. 6/6 is the visual acuity needed to discriminate two contours separated by 1 arc minute- 1.75 mm at 6 meters. This is because a 6/6 letter, E for example, has three limbs and two spaces in between them, giving 5 different detailed areas. The ability to resolve this therefore requires 1/5 of the letter's total size, which in this case would be 1 minute (visual angle). The significance of the 6/6 standard can best be thought of as the lower limit of normal or as a screening cutoff. When used as a screening test, subjects that reach this level need no further investigation, even though the average visual acuity with a healthy visual system is typically better.

text: Some people may suffer from other visual problems, such as color blindness, reduced contrast, mild amblyopia, cerebral visual impairments, inability to track fast-moving objects, or one of many other visual impairments and still have "normal" visual acuity. Thus, "normal" visual acuity by no means implies normal vision. The reason visual acuity is very widely used is that it is easily measured, its reduction (after correction) often indicates some disturbance, and that it often corresponds with the normal daily activities a person can handle, and evaluates their impairment to do them (even though there is heavy debate over that relationship).

text: Other measures[edit]

text: Normally, visual acuity refers to the ability to resolve two separated points or lines, but there are other measures of the ability of the visual system to discern spatial differences.

text: Vernier acuity measures the ability to align two line segments. Humans can do this with remarkable accuracy. This success is sometimes regarded as hyperacuity. Under optimal conditions of good illumination, high contrast, and long line segments, the limit to vernier acuity is about 8 arc seconds or 0.13 arc minutes, compared to about 0.6 arc minutes (6/4) for normal visual acuity or the 0.4 arc minute diameter of a foveal cone. Because the limit of vernier acuity is well below that imposed on regular visual acuity by the "retinal grain" or size of the foveal cones, it is thought to be a process of the visual cortex rather than the retina. Supporting this idea, vernier acuity seems to correspond very closely (and may have the same underlying mechanism) enabling one to discern very slight differences in the orientations of two lines, where orientation is known to be processed in the visual cortex.

text: The smallest detectable visual angle produced by a single fine dark line against a uniformly illuminated background is also much less than foveal cone size or regular visual acuity. In this case, under optimal conditions, the limit is about 0.5 arc seconds or only about 2% of the diameter of a foveal cone. This produces a contrast of about 1% with the illumination of surrounding cones. The mechanism of detection is the ability to detect such small differences in contrast or illumination, and does not depend on the angular width of the bar, which cannot be discerned. Thus as the line gets finer, it appears to get fainter but not thinner.

text: Stereoscopic acuity is the ability to detect differences in depth with the two eyes. For more complex targets, stereoacuity is similar to normal monocular visual acuity, or around 0.6–1.0 arc minutes, but for much simpler targets, such as vertical rods, may be as low as only 2 arc seconds. Although stereoacuity normally corresponds very well with monocular acuity, it may be very poor, or absent, even in subjects with normal monocular acuities. Such individuals typically have abnormal visual development when they are very young, such as an alternating strabismus, or eye turn, where both eyes rarely, or never, point in the same direction and therefore do not function together.

text: Motion acuity[edit]

text: The eye has acuity limits for detecting motion.[25] Forward motion is limited by the subtended angular velocity detection threshold (SAVT), and horizontal and vertical motion acuity are limited by lateral motion thresholds. The lateral motion limit is generally below the looming motion limit, and for an object of a given size, lateral motion becomes the more insightful of the two, once the observer moves sufficiently far away from the path of travel. Below these thresholds subjective constancy is experienced in accordance with the Stevens' power law and Weber–Fechner law.

text: Subtended angular velocity detection threshold (SAVT)[edit]

text:
There is a specific acuity limit in detecting an approaching object's looming motion.[26][27] This is regarded as the subtended angular velocity detection threshold (SAVT) limit of visual acuity.[28] It has a practical value of 0.0275 rad/s.[29] For a person with SAVT limit of

θ
˙

t

{\displaystyle {\dot {\theta }}_{t}}

, the looming motion of a directly approaching object of size S, moving at velocity v, is not delectable until its distance D is[26]

text: where the S2/4 term is omitted for small objects relative to great distances by small-angle approximation.

text:
In order to exceed the SVAT, an object of size S moving as velocity v must be closer than D; beyond that distance, subjective constancy is experienced. The SVAT

θ
˙

t

{\displaystyle {\dot {\theta }}_{t}}

 can be measured from the distance at which a looming object is first detected:

text: where the S2 term is omitted for small objects relative to great distances by small-angle approximation.

text: The SAVT has the same kind of importance to driving safety and sports as the static limit. The formula is derived from taking the derivative of the visual angle with respect to distance, and then multiplying by velocity to obtain the time rate of visual expansion (dθ/dt = dθ/dx · dx/dt).

text: Lateral motion[edit]

text:
There are acuity limits (

θ
˙

t

{\displaystyle {\dot {\theta }}_{t}}

) of horizontal and vertical motion as well.[25] They can be measured and defined by the threshold detection of movement of an object traveling at distance D and velocity v orthogonal to the direction of view, from a set-back distance B with the formula

text: Because the tangent of the subtended angle is the ratio of the orthogonal distance to the set-back distance, the angular time rate (rad/s) of lateral motion is simply the derivative of the inverse tangent multiplied by the velocity (dθ/dt = dθ/dx · dx/dt). In application this means that an orthogonally traveling object will not be discernible as moving until it has reached the distance

text:
where

θ
˙

t

{\displaystyle {\dot {\theta }}_{t}}

 for lateral motion is generally ≥ 0.0087 rad/s with probable dependence on deviation from the fovia and movement orientation,[25] velocity is in terms of the distance units, and zero distance is straight ahead. Far object distances, close set-backs, and low velocities generally lower the salience of lateral motion. Detection with close or null set-back can be accomplished through the pure scale changes of looming motion.[27]

text: Radial motion[edit]

text:
The motion acuity limit affects radial motion in accordance to its definition, hence the ratio of the velocity v to the radius R must exceed

θ
˙

t

{\displaystyle {\dot {\theta }}_{t}}

:

text: Radial motion is encountered in clinical and research environments, in dome theaters, and in virtual-reality headsets.


document_title: Yuma, Arizona

question_text: what is the highest temperature in yuma az

root

text: Yuma, Arizona

text: History[edit]

text: The area's first settlers for thousands of years were Native American cultures and historic tribes. Their descendants now occupy the Cocopah and Quechan reservations.

tag: p

text: In 1540, Spanish colonial expeditions under Hernando de Alarcon and Melchior Diaz visited the area and immediately recognized the natural crossing of the Colorado River as an ideal spot for a city. The Colorado River narrows to slightly under 1,000 feet wide in one area. Military expeditions that crossed the Colorado River at the Yuma Crossing include Juan Bautista de Anza (1774), the Mormon Battalion (1848) and the California Column (1862).

text: During and after the California Gold Rush to the late 1870s, the Yuma Crossing was known for its ferry crossings for the Southern Emigrant Trail. This was considered the gateway to California, as it was one of the few natural spots where travelers could cross the otherwise very wide Colorado River.

text: First settlements[edit]

text: Following the United States establishing Fort Yuma, two towns developed one mile downriver. The one on the California side was called Jaeger City, named after the owner of Jaeger's Ferry, which crossed the river there.  It was for a time the larger of the two, with the Butterfield Overland Mail office and station, two blacksmiths, a hotel, two stores, and other dwellings.[8]

text: The other was called Colorado City. Developed on the south side of the river in what is now Arizona by speculator Charles Poston, it was the site of the custom house. When started, it was just north of the border between Mexican-ruled Sonora, Mexico and California.  After the Gadsden Purchase by the United States, the town bordered on the Territory of New Mexico. This area was designated as the Territory of Arizona in 1863.  The Colorado City site at the time was duly registered in San Diego; both banks of the Colorado River just below its confluence with the Gila were recognized as being within the jurisdiction of California.  The county of San Diego collected taxes from there for many years.[8][9]

text: From 1853 a smaller settlement, Arizona City, grew up on the high ground across from the fort and was organized under the name of its post office in 1858.  It had adobe dwellings, two stores and two saloons. Colorado City and Jaeger City were almost completely destroyed by the Great Flood of 1862 and had to be rebuilt on higher ground. At that time Colorado City became part of Arizona City.[8][10]  It took the name Yuma in 1873.

text: Early development[edit]

text: From 1854, Colorado City was the major steamboat stop for traffic up and down the Colorado River.  After the 1862 flood, it became part of Arizona City.  The steamboats transported passengers and equipment for the various mines and military outposts along the Colorado; Colorado City was the terminus of wagon traffic up the Gila River into New Mexico Territory.  They offloaded the cargo from ships at the mouth of the Colorado River at Robinson's Landing and from 1864 at Port Isabel.  From 1864, the Yuma Quartermaster Depot, today a state historic park, supplied all forts in present-day Arizona, as well as large parts of Colorado and New Mexico. After Arizona became a separate territory, Yuma became the county seat for Yuma County in 1871, replacing La Paz, the first seat.

text: The Southern Pacific Railroad bridged the river in 1877, and acquired George Alonzo Johnson's Colorado Steam Navigation Company, the only steamboat company on the river.  Yuma became the new base of navigation on the river, ending the need for Port Isabel, which was abandoned in 1879.  The warehouses and shipyard there were moved to Yuma.

text: Government[edit]

text: Organization[edit]

text: The city of Yuma operates as a charter city  under the Charter of the City of Yuma.[11] The elected government of the city is the City Council which follows the mayor–council government system and whose members include the following:

text: Mayor[edit]

text: The Mayor of the City of Yuma acts as the chief executive officer of the city, and is elected for a period of four years.  The mayor is elected from the city at large. The mayor has the following powers and responsibilities: act as an ex officio chairman of the city council (ensuring that all ordinances thereof are enforced), call and preside over meetings, administer oaths and issue proclamations. The mayor is also recognized as the official head of the city by the courts and has the power to take command of the police and govern the city by proclamation during times of great danger.[11]

text: City Council[edit]

text:
The City of Yuma City Council is the governing body of the City of Yuma and is vested with all powers of legislation in municipal affairs. The council is composed of six council members elected from the city at large for four-year terms, as well as the Mayor of Yuma. A deputy mayor is also elected by the Council who shall act as Mayor during the temporary absence of the mayor.
[11]

text: City Administrator[edit]

text: The City Council appoints a city administrator who acts as the chief administrative officer of the city. The city administrator is directly responsible to the City Council for the administration of all city affairs placed in his charge by the City Charter, or by ordinances passed by the Council. Some of the administrator's duties include: see that all laws and provisions of the City Charter are faithfully executed, prepare and submit the annual budget and capital program to the City Council and keep the City Council fully advised as to the financial condition and future needs of the city.[11]

text: Geography[edit]

text: Yuma is located near the borders of California to the west and Mexico to the south, and just west of the Gila River's confluence with the Colorado. The city is approximately 60 miles from the Gulf of California (Sea of Cortez), a branch of the Pacific.

text: According to the United States Census Bureau, the city has a total area of 106.7 square miles (276 km2), of which 106.6 square miles (276 km2) is land and 0.1 square miles (0.26 km2) (0.07%) is water.

text: Climate[edit]

text: Yuma is noted for its weather extremes.  Of any populated place in the contiguous United States, Yuma is the driest, the sunniest, and the least humid, has the lowest frequency of precipitation, and has the highest number of days per year–175–with a daily maximum temperature of 90 °F (32 °C) or higher.[12][13]

text: Yuma features a hot desert climate (Köppen climate classification BWh), with extremely hot summers and warm winters. Atmospheric humidity is usually very low except during what are called "Gulf surges", when a maritime tropical air mass from the Gulf of California is drawn northward, usually in connection with the summer monsoon or the passage of a tropical storm to the south.

text: The sun is said to shine during about 90% of the daylight hours, making Yuma the sunniest place in the world.[14] An annual mean sunshine duration of 4,015 h would have been recorded in the desert city.[13][15]

text: On average, Yuma receives 3.36 inches (85 mm) of rain annually. Even in the wettest year of 2005, only 7.39 in (188 mm) fell. The driest year at Yuma Airport has been 2007, with only 0.15 in (3.8 mm) recorded. On average, August and September are the wettest months of the year, while June is the driest.

text: In 1995, Yuma reached its all-time high of 124 °F (51 °C).[16] The lowest recorded temperature was −6 °C (21 °F) on the Yuma-Mesa area in January 2007.  The temperature fell to −6 °C (21 °F) for approximately two hours and harmed many crops grown in and around Yuma. The crop that suffered the most damage was the citrus on the Yuma mesa, most notably the lemon crop. It suffered a 75% to 95% loss of crop and trees, as stated by the Arizona Department of Agriculture in a February 2007 report. On average, the temperature lowers to the freezing mark in less than a quarter of years, and there are 118 days per year that reach or exceed 100 °F (38 °C), usually from April through October. During July and August the temperature fails to reach the century mark on at most, only a few days.

text: In 1997, the desert city sustained a full tropical storm after Hurricane Nora made landfall at the mouth of the Colorado River and quickly moved due north along it. This rare event cut power to 12,000 customers in Yuma, and dropped 3.59 inches (91 mm) of rain at Marine Corps Air Station Yuma. The last time a hurricane had hit near Yuma was in mid-August 1977, when similar falls were recorded.

text:
hideClimate data for Yuma, Arizona (Yuma Int'l), 1981–2010 normals,[a] extremes 1878–present

Month

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Year

Record high °F (°C)

88 (31)

97 (36)

102 (39)

107 (42)

120 (49)

122 (50)

124 (51)

120 (49)

123 (51)

112 (44)

98 (37)

91 (33)

124 (51)

Mean maximum °F (°C)

79.4 (26.3)

85.0 (29.4)

92.9 (33.8)

100.0 (37.8)

106.8 (41.6)

112.6 (44.8)

114.7 (45.9)

114.3 (45.7)

110.8 (43.8)

102.1 (38.9)

89.1 (31.7)

77.8 (25.4)

116.2 (46.8)

Average high °F (°C)

69.6 (20.9)

73.8 (23.2)

79.9 (26.6)

86.4 (30.2)

95.3 (35.2)

103.5 (39.7)

106.8 (41.6)

106.2 (41.2)

101.3 (38.5)

89.9 (32.2)

77.5 (25.3)

68.3 (20.2)

88.2 (31.2)

Average low °F (°C)

47.6 (8.7)

50.1 (10.1)

54.4 (12.4)

59.6 (15.3)

67.3 (19.6)

74.6 (23.7)

82.1 (27.8)

82.3 (27.9)

76.5 (24.7)

65.0 (18.3)

53.9 (12.2)

46.6 (8.1)

63.3 (17.4)

Mean minimum °F (°C)

37.3 (2.9)

39.7 (4.3)

43.9 (6.6)

49.1 (9.5)

56.4 (13.6)

64.3 (17.9)

74.1 (23.4)

73.6 (23.1)

65.3 (18.5)

54.2 (12.3)

43.1 (6.2)

36.4 (2.4)

34.6 (1.4)

Record low °F (°C)

22 (−6)

25 (−4)

31 (−1)

38 (3)

39 (4)

50 (10)

61 (16)

58 (14)

50 (10)

35 (2)

29 (−2)

22 (−6)

22 (−6)

Average precipitation inches (mm)

0.36 (9.1)

0.33 (8.4)

0.34 (8.6)

0.12 (3)

0.03 (0.8)

0.01 (0.3)

0.26 (6.6)

0.52 (13.2)

0.53 (13.5)

0.21 (5.3)

0.20 (5.1)

0.45 (11.4)

3.36 (85.3)

Average precipitation days (≥ 0.01 in)

2.3

2.0

1.8

.8

.4

.2

.9

2.3

1.2

1.1

1.0

2.1

16.2

Mean monthly sunshine hours

268.4

270.8

335.5

365.5

407.4

415.4

392.6

375.6

341.7

319.6

270.1

252.7

4,015.3

Percent possible sunshine

84

88

90

94

95

97

90

91

92

91

86

81

90

Source: NOAA[17][18]

tag: table

text: Demographics[edit]

text:
Historical population

Census
Pop.

%±
18701,144—18801,2004.9%18901,77347.8%19001,519−14.3%19102,91491.8%19204,23745.4%19304,89215.5%19405,3258.9%19509,14571.7%196023,974162.2%197029,00721.0%198042,48146.5%199056,96634.1%200077,51536.1%201093,06420.1%Est. 201795,502[4]2.6%U.S. Decennial Census[19]

text: As of the census of 2010, there were 93,064 people. There were 38,626 housing units in Yuma city, 79.5% of which were occupied housing units. The racial makeup of the city was 68.8% White, 3.2% Black or African American, 1.8% Native American, 1.9% Asian, 0.2% Pacific Islander, and 4.5% from two or more races. 54.8% of the population were Hispanic or Latino of any race.[20]

text: As of the census of 2000, there were 77,515 people, 26,649 households, and 19,613 families residing in the city. The population density was 726.8 people per square mile (280.6/km²). There were 34,475 housing units at an average density of 323.3 per square mile (124.8/km²). The racial makeup of the city was 68.3% White, 3.2% Black or African American, 1.5% Native American, 1.5% Asian, 0.2% Pacific Islander, 21.4% from other races, and 3.9% from two or more races. 45.7% of the population were Hispanic or Latino of any race.

text: There were 26,649 households out of which 38.8% had children under the age of 18 living with them, 56.6% were married couples living together, 13.1% had a female householder with no husband present, and 26.4% were non-families. 21.7% of all households were made up of individuals and 9.8% had someone living alone who was 65 years of age or older. The average household size was 2.79 and the average family size was 3.27.

text: In the city, the population was spread out with 29.6% under the age of 18, 11.9% from 18 to 24, 27.1% from 25 to 44, 17.5% from 45 to 64, and 13.9% who were 65 years of age or older. The median age was 31 years. For every 100 females, there were 99.1 males. For every 100 females age 18 and over, there were 97.2 males.

text: According to the 2006 American Community Survey estimate, the median income for a household in the city was $39,885, and the median income for a family was $41,588. Males had a median income of $35,440 versus $27,035 for females. The per capita income for the city was $18,393. About 14.1% of families and 16.9% of the population were below the poverty line, including 23.4% of those under age 18 and 13.9% of those age 65 or over.

text: High unemployment remains an issue in Yuma. Citing April 2014 data, the Bureau of Labor Statistics ranked Yuma as having the highest unemployment rate in the United States at 23.8 percent, above the 21.6 percent in El Centro, California.[21] Yuma's agricultural workforce, which adjusts to the picking season, is cited by the Arizona Department of Commerce as the reason for the apparent high unemployment.[22]

text: Economy[edit]

text: The Yuma Metropolitan Statistical Area has the highest unemployment rate in the United States as of 2018 at 20.9%.[23] A large percentage of the work force is employed seasonally in agriculture, contributing to apparent unemployment.

text: Top employers[edit]

text: According to the City's 2016 Comprehensive Annual Financial Report,[24] the top employers in the Yuma Metropolitan Statistical Area in 2015 were:

text:
#

Employer

# of employees

1

Marine Corps Air Station Yuma

6,825

2

Yuma Proving Ground

2,093

3

Yuma Regional Medical Center

1,991

4

Datepac

1,500

5

Yuma Elementary School District

1,400

6

Yuma County

1,366

7

TRAX International

1,262

8

City of Yuma

1,200

9

United States Border Patrol

1,000

10

Yuma Union High School District

1,000

text: Other large employers include Bose, Dole Fresh Vegetables and Shaw Industries.[25]

text: Arts and culture[edit]

text: Yuma contains the historical Yuma Territorial Prison, the Yuma Quartermaster Depot State Historic Park (formerly known as the Yuma Crossing Historic Park), and a historic downtown area. Yuma is an Arizona Main Street City. Because of budget cutbacks at the state level, Arizona State Parks no longer operates the Territorial Prison and Quartermaster Depot. They are now operated by the Yuma Crossing National Heritage Area and the City of Yuma. The Yuma Visitors' Bureau oversees the Welcome Center at the Quartermaster Depot and is the official visitors' center for the Yuma Community.

text: Near Yuma are the Kofa Mountain Range and wildlife refuge, Martinez and Mittry Lakes, and the Algodones Dunes.

text: The city is the location of the Marine Corps Air Station Yuma, which conducts an annual air show and many large-scale military exercises. There is also the Yuma Proving Ground, an Army base that tests new military equipment. Yuma Proving Ground is also home to the Special Operations Free Fall School, which provides training in free-fall parachute operations to Special Forces units in all branches of service, as well as those of other nations.

text: The Colorado River runs along the north and west side of town, serving as the border between Arizona and California. Yuma is an important station for trucking industry movement of goods between California, Arizona and Mexico.

text: The Rialto movie theatre once owned a Kilgen pipe organ, one of the most expensive pipe organs to have been made. Originally played as accompaniment to silent films, it has been moved to the Yuma Theatre.

text: Every February residents and visitors enjoy the annual rodeo, the Yuma Jaycees Silver Spur Rodeo. A parade opens the events. Cowboys and cowgirls from all over the country compete in the festivities.

text: The Yuma County Fair takes place annually in the spring at the fairgrounds in Yuma.

text: Filming[edit]

text: A number of movies have been shot in the Yuma area, including The Sheik (1921), Beau Geste (1926), Beau Geste (1939), Beau Geste (1966), Gunga Din (1939), Flight of the Phoenix (1966), Return of the Jedi (1983) and Spaceballs (1987).[26]

text: Sports[edit]

text: Yuma has a minor-league-caliber ballpark, Desert Sun Stadium, which was home to the Yuma Desert Rats of the North American League and site of home games of two (previously four) teams for the Arizona Winter League.[27] The San Diego Padres used the field as a spring training facility from 1969 until 1993.[28] and a Japanese baseball team, the Yakult Swallows, used the field for spring training from 1995 to 2015.[29] Many local club sports exist in the area as well, including the Yuma Sidewinders Rugby Football Club. The rugby team participates in the Division III Arizona Men's Rugby League, and travels throughout Arizona, California and Nevada, as well as playing home games in Yuma.

text: Education[edit]

text: The city is zoned to the Yuma Union High School District. Yuma has five public high schools: Yuma Union High School, Kofa High School, Cibola High School, Gila Ridge High School, Vista Alternative High School; and the private Yuma Catholic High School and Calvary Baptist School. Yuma also has four charter high schools: AZTEC High School, Carpe Diem Collegiate High School, Harvest Preparatory Academy, and YPIC Charter High School.

text: Yuma has two main elementary school districts, District One and Crane District, which include several schools as well as junior high schools. Yuma has four charter elementary school: AmeriSchools Academy North and South, Harvest Preparatory Academy, and Desert View Academy.

text: Additionally, Yuma has 6 six private elementary schools: Yuma Lutheran School, Yuma Adventist Christian School, Immaculate Conception School, St. Francis of Assisi School, Calvary Baptist School and Southwestern Christian School.[30]

text: Arizona Western College is Yuma's community college, serving primarily as a choice for transfer students and those with shorter career goals.

text: Northern Arizona University has a branch campus in Yuma, as does the for-profit University of Phoenix.

text: Yuma is served by the Yuma County Library District which consists of a Main Library and several branches, including sites in Somerton, Wellton, Fortuna Foothills, and San Luis. A new main state-of-the-art library is now open.

text: Media[edit]

text:
Yuma Sun newspaper
KYMA NBC Affiliate
KECY-TV FOX, ABC, CW and Telemundo Affiliate
KSWT CBS Affiliate
KCFY 88.1 KCFY Christian Radio
KAWC-FM 88.9 FM Public Radio (Arizona Western College)
KYRM 91.9 FM Radio Manantial
KLJZ 93.1 FM Soft Rock Radio
KTTI 95.1 FM Country Radio
KQSR 100.9 FM Soft Rock Radio
KCEC 104.5 FM Regional Mexican Radio
KBLU 560 AM Talk Radio
KOFA 1320 AM Public Radio (Arizona Western College)
KCYK 1400 AM Country Radio

tag: ul

text: Transportation[edit]

text:
Yuma County Area Transit
Yuma International Airport
Yuma Station (Amtrak)
Camel Express to Quartzsite, Arizona[31]
Interstate 8

text: Notable people[edit]

text:
Darrell Bevell Arizona Cardinals Offensive Coordinator
Alex Barrett (born 1994), American football player
Ryan Bedford, Olympic speed skater
Charles Brinley, actor of the silent era
Cesar Chavez, Mexican American civil rights leader
Tom Childs, miner and rancher
Curley Culp, NFL player for Kansas City Chiefs, member of Pro Football Hall of Fame
Jason DeCorse, guitarist for The Icarus Line
Efrain Escudero, NCAA All-American wrestler, current mixed martial artist, former UFC fighter, and The Ultimate Fighter Season 8 reality TV show champion
Edgar Garcia, current mixed martial artist, and former UFC and WEC fighter
Irving Garcia, USL Pro player for Los Angeles Blues
Kelvin Gastelum, Ultimate Fighter 17 reality TV show champion, and current UFC fighter in the Middleweight division.
Bill Hudson, Alaska state legislator
Ron Jessie, NFL wide receiver for Los Angeles Rams
Robert Wilson Kennerly, retired politician and community leader
Curtis Lee, singer
Jonathan Lines, businessman, Chair of Arizona Republican Party
Jose Maria Redondo, entrepreneur and former mayor of Yuma
Mike Marshall, manager of Yuma Scorpions, won two World Series rings with Los Angeles Dodgers
Bengie Molina, Major League Baseball catcher for the Texas Rangers; played shortstop for Arizona Western College in 1991 and 1992
Bobby Pacho, 1930s professional boxer and Welterweight world title contender
Bob Porter, major league baseball player
DeForest Porter, mayor of Phoenix; Justice, Arizona Territory Supreme Court[32]
John Shanssey, boxer, gambler, saloon owner, and Mayor of Yuma
Cain Velasquez, two-time UFC heavyweight champion, two-time All-American collegiate wrestler
Roger L. Worsley, educator; lived in Yuma, 1959 to 1963