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Topic: Acuity

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Visual acuity - Wikipedia, the free encyclopedia 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 Tumbling E. Visual acuity is typically measured monocularly rather than binocularly with the aid of an optotype chart for distant vision, an optotype chart for near vision, and an occluder to cover the eye not being tested. Visual acuity depends upon how accurately light is focused on the retina (mostly the macular region), the integrity of the eye's neural elements, and the interpretative faculty of the brain en.wikipedia.org /wiki/Visual_acuity   (2466 words)

LaserMyEye :: Encyclopedia :: Visual acuity Visual acuity does not seek to measure all aspects of vision, but it does measure a very important feature, because in healthy eyes which have not undergone surgery, the normal cause of poor testing in a standard acuity test is refractive error (myopia, hyperopia and/or astigmatism), which can be corrected with glasses or contact lenses. Visual acuity can also separately be assesed for near vision (most relevant to presbyopes, people usually in their 40's or later who lose the ability to focus up close) using a small chart held nearer the patient. Visual acuity is assessed utilising a Snellen eyechart and the "better 1, better 2" subjective testing method called a refraction; acuity is normally measured in each eye individually and in both eyes together. www.lasermyeye.org /encyclopedia/acuity.html   (244 words)

Activity 3A: Measuring Visual Acuity Visual acuity is a measure of the resolving power of the eye, particularly with its ability to distinguish letters and numbers at a given distance. The visual acuity is reported as a ratio with the top number being the distance and the bottom number the angle formed by the letter and the eye. The measure of visual acuity is the angle formed between the eye and the letter. teachhealthk-12.uthscsa.edu /pa/pa06/0603A.htm   (359 words)

Encyclopedia - Visual Acuity Overall visual acuity is measured by using the Snellen Eye Chart, with the large E at the top followed by rows of letters where each row is smaller than the previous one. Visual acuity is the medical term for sharpness of vision. The results of visual acuity tests are used to prescribe eyeglasses or other corrective measures. www.visionrx.com /library/enc/enc_acuity.asp   (376 words)

Visual Acuity The reason that the number “20” is used in visual acuity measurements is because, in the United States, the standard length of an eye exam room (that is, the distance from the patient to the acuity chart) is about 20 feet. Visual acuity often is referred to as “Snellen” acuity. The less the bottom number in the visual acuity ratio, the better the acuity; and the greater the bottom number, the worse the acuity. www.tedmontgomery.com /the_eye/acuity.html   (1309 words)

Visual Acuity Acuity was assessed either during the eye clinic visit or during a home or school visit in conjunction with an assessment for the longitudinal study. Out of the 48 subjects that were examined, numeric visual acuities were obtained on 42, a gross measure of acuity on 5, and no measure on 1.Due to their short attention spans and some "autistic-like" behaviors, boys with FXS were challenging to examine. Visual problems are not as prevalent in the population of young boys with fragile X syndrome as earlier studies indicate. www.fpg.unc.edu /~fx/Pages/visual.htm   (547 words)

2020 vision and visual acuity Visual acuity is a measure of the spatial resolving power of the visual system; it indicates the angular size of the smallest detail that can be resolved. Visual acuity measurements are also used by some licensing authorities and employers as eligibility criteria for some occupations (e.g., airline pilot, police officer) and activities (e.g., driving). In the diagnosis and monitoring of eye diseases that may affect vision, changes of visual acuity are often taken to indicate the presence and magnitude of change in the eye condition. www.agingeye.net /visionbasics/healthyvision.php   (872 words)

Visual Acuity and Contrast Sensitivity Visual acuity is the ability to see fine detail, for example, reading signs on the road, seeing separate stars in the night sky, and seeing a small white spot on a dark surface. Visual acuity is expressed as a number representing the smallest object or feature that the person can see. Acuity cannot always be tested in small children at 20 ft. The Snellen fraction is different, depending upon the test distance. www.e-advisor.us /Luisa/acuity_CS.htm   (611 words)

Spatial Resolution (Visual Acuity) The standard definition of normal visual acuity is the ability to resolve a spatial pattern separated by a visual angle of one minute of arc. Simply put, 20/20 means that you are able to see on an eye chart at 20 feet that which a person with normal visual acuity can see. Most of us have had our visual acuity checked. www.yorku.ca /eye/acuity.htm   (383 words)

Visual Acuity in Sensory Substitution for the Blind These figures mean that visual acuity is between 8 and 12 times less than with normal human vision, so it would be characterised by a visual acuity in the range 20/160 to 20/240, which would be around the 20/200 that defines the verge of legal blindness. Although visual acuity of humans may still be measured in the same way even if they have tunnel vision, we should not allow that with The vOICe or other vision substitution devices in order to get fair and meaningful figures. In other words, in measuring visual acuity of a vision substitution device, it should in principle not be allowed to manually sweep the camera. www.seeingwithsound.com /acuity.htm   (2409 words)

Lesson 3: Measuring Visual Acuity Visual acuity is typically reported as a ratio with the distance for the test being the top number and the angle of resolution (in minutes of arc) the bottom number. A visual acuity sheet for near vision (ETDRS) is provided for students to measure each other's acuity at different distances and then graph the results. Students should be aware that visual acuity is only one of the functional aspects of seeing. teachhealthk-12.uthscsa.edu /pa/pa06/0603.htm   (178 words)

Visual Acuity Tests The basic visual acuity test is the line test where the distance between the symbols, the optotypes, is equal to the width of the symbols, as recommended by the International Council of Ophthalmology in 1989. Visual acuity for distance vision is measured with tests held at three meter distance. Visual acuity at near is measured with the line test which is the basic measurement. www.lea-test.fi /en/vistests/pediatric/vactests/vatests.html   (855 words)

Webvision: Spatial Resolution Visual acuity is limited by diffraction, aberrations and photoreceptor density in the eye (Smith and Atchison, 1997). Visual acuity measurement in the clinic use high contrast, that is, black letters on a white background. Visual acuity measured in this way is called Vernier acuity (a type of hyperacuity) and the discontinuity is specified in terms of its angular size (figure 7). webvision.med.utah.edu /KallSpatial.html   (4199 words)

A New Perspective - Visual Acuity Visual acuity is most often measured using eye charts, the Snellen chart (named after it's inventor) is the one most often used, though there are charts, such as the Feinbloom chart, which are specially designed to be used to measure low vision Visual acuity is the clarity or sharpness of the image that someone sees. A visual acuity recorded as 10/200 means that a person can see the 200-sized number (the "Big E") from ten feet away—in more familiar terms, they have 20/400 vision. members.shaw.ca /jen_jesso/eyes/acuity.htm   (926 words)

Dynamic Visual Acuity Test DVA: VOR Impairment Assessments: NeuroCom - Products: Protocols In normal individuals, losses in visual acuity are minimized during head movements by the vestibular ocular reflex (VOR) system that maintains the direction of gaze on an external target by driving the eyes in the opposite direction of the head movement. For each movement axis, the static visual acuity protocol described above is repeated with the following modifications: The patient wears a sensor that continuously measures the position and velocity of head movements and the optotype "E" appears ONLY while the head is moving in the prescribed direction and minimum velocity. To quantify losses in visual acuity during head movement, the first step is to determine the patient's head fixed (static) visual acuity. www.onbalance.com /neurocom/protocols/VORImpairment/dva.aspx   (637 words)

[Clinical Preventive Services] Screening for Visual Impairment Visual acuity tests for children include the Snellen chart, the Landolt C, the tumbling E, the Allen picture cards, grating cards, and others.25 The specificity of any acuity test for detecting strabismus or amblyopia is imperfect as other conditions may be the cause of the diminished acuity. A community-based examination of all first- to third-grade children in 1984 found visual acuity of 20/30 or better in the better eye in 94-95% of the schoolchildren; 7%, 9%, and 9% of children in first, second, and third grades, respectively, had glasses prescribed. Impaired visual acuity is readily detected by use of a Snellen chart. cpmcnet.columbia.edu /texts/gcps/gcps0043.html   (2578 words)

Peripheral Visual Acuity Assessment - Introduction This relationship between visual acuity and the retinal eccentricity of the target is the focus of the current experiment. However, visual acuity declines rapidly as the location of the retinal image of the stimulus moves away from the fovea. Visual acuity, in its most basic form, refers to our ability to resolve fine spatial detail. www.usd.edu /coglab/IntroPeripheral.html   (701 words)

Bilberry & Night Visual Acuity Visual acuity was tested with individual Landolt C targets, where the size of the opening in the C and the thickness of the letter corresponded to the size of the spaces and bars in the more familiar Snellen letter E. Visual acuity was selected partly because it has been an accepted vision standard for clinical and legal purposes for many years. The current study failed to find any effect of bilberry on night visual acuity or night contrast sensitivity using a high dose of bilberry taken for a significant duration. www.thorne.com /altmedrev/fulltext/bilberry5-2.html   (3267 words)

Visual Acuity For the case of normal visual acuity the angle Theta is 1/60 of a degree. The standard definition of normal visual acuity (20/20 vision) is the ability to resolve a spatial pattern separated by a visual angle of one minute of arc. At 12 inches, the normal visual acuity of the human eye is 0.00349 inch. www.ndt-ed.org /EducationResources/CommunityCollege/PenetrantTest/Introduction/visualacuity.htm   (512 words)

Vision - visual acuity Visual acuity is the ability to distinguish details and shapes of objects. A visual acuity test is performed by placing an eyechart twenty feet away from a patient and having them read the eyechart to the smallest letters they can see. Also called central vision, visual acuity is a very important statistic in the eye doctor's office. www.suncoastretina.com /Procedures/VisualAcuity.htm   (303 words)

Apparatus for visual acuity test - Patent 5416540 Each Landolt ring chart for visual acuity value 0.7 in the test chart line 8 is 10.39 mm in outer diameter and the visual angle of slit is 1.4' if seen at a distance of 5 m, it can be accordingly disposed in a space of 15 mm without overlapping on another test chart line. In the liquid crystal plate 1, numeral 15 is a digital display portion to indicate the lowest visual acuity value of displayed test charts and numeral 16 is a digital display portion to indicate the highest visual acuity value of the same. In addition, there is also an apparatus for visual acuity test in which different kinds of test charts can be utilized by exchanging test chart plates, for instance, from a test chart plate provided with Landolt rings thereon to another test chart plate provided with character charts thereon. www.freepatentsonline.com /5416540.html   (3081 words)

Visual Acuity - Acuity is an organization formed to provide expert advice, services and software to the fast growing number of applications and users of large scale visualization devices. Visual Acuity - Acuity is an organization formed to provide expert advice, services and software to the fast growing number of applications and users of large scale visualization devices. We have a considerable track record, both as individuals and as a team in the creation and execution of visualization content and systems for public, corporate and engineering applications. Our breadth of experience ranges from issues as diverse as space and visitor flow planning, to new media and digital content, technology and architectural impact. www.visual-acuity.com   (101 words)

Eye Tests > Visual acuity -- EyeMDLink.com If an individual has 20/40 acuity, he or she requires an object to be at 20 feet to visualize it with the same resolution as an individual with 20/20 acuity would when the object was at 40 feet. In most states, visual acuity must be 20/40 or better with best correction in place, in at least one eye, to pass a drivers licensing test. The measurement of visual acuity is likely the most important aspect of a complete eye examination. www.eyemdlink.com /Test.asp?TestID=32   (194 words)

Visual Acuity Tests It is wise to measure visual acuity with the same optotypes at distance and at near. If a person's visual acuity at distance has decreased from an earlier measured value but visual acuity at near is the same as before, the person has become slightly myopic in that eye. In the examination of adult persons visual acuity is usually measured first at distance using a chart and near vision acuity after that either with a near vision card or as reading acuity. www.lea-test.fi /en/vistests/occupati/vac/occ_va.html   (463 words)

visual_acuity [n] sharpness of vision; the visual ability to resolve fine detail (usually measured by a Snellen chart). lookwayup.com /lwu.exe/lwu/d?s=f&w=visual_acuity   (17 words)

How Visual Acuity Is Measured When checking visual acuity, one eye is covered at a time and the vision of each eye is recorded separately, as well as both eyes together. If 20/20 is considered 100% visual effiency, 20/40 visual acuity is 85% efficient. They give no information as to whether or not meaning is obtained from visual input, how much effort is needed to see clearly or singly, and whether or not vision is less efficient when using both eyes as opposed to each eye individually. www.mdsupport.org /library/acuity.html   (716 words)

CITY Visual Systems, Computerised Vision Screening for Computer Users, Drivers and School Children On investigation, it has been found that a small number of these complaints are due to actual visual problems that may be corrected by a visit to the optometrist. Based upon years of research, it looks at visual and related problems and provides various reports and advice that relate to the computer user. This program has been in commercial use around the world since 1992 and is used in over 3,000 workplaces, including blue chip companies, governments (national, regional and local), optometric practices, hospitals, small business, schools and universities. www.cityvisual.com   (384 words)

Avian Visual Attention in Science and Culture The scientific study of animal intelligence, including visual attention, typically makes an implicit distinction between intellectual and emotional components of an animal’s life, in the sense that the science usually acts as though its proper goal is a purely objective analysis of the nonhuman animal mind. Our own three examples of research on avian visual attention reveal their intellectual heritage in a science that acts as though it is independent of the surrounding culture, including human values. Since complex stimuli having specified quantitative properties are essential to much research on avian visual cognition, this is equivalent to saying that avian cognition is highly dependent on the surrounding culture, specifically, on the culture’s technological resources. www.pigeon.psy.tufts.edu /avc/shimp   (14260 words)

Measuring visual acuity The Snellen eye chart is the typical eye chart used to measure visual acuity during clinical eye examinations. The ETDRS eye chart, composed of 5 letters per line, is the gold standard used in measuring visual acuity for clinical research purposes. The Snellen fractions, 20/20, 20/30, etc. relate to the ability to identify a letter of a certain size from a specified distance. www.amdalliance.org /amd-info/professional/assessing/measuring-visual.asp   (94 words)

Visual acuity test definition - Medical Dictionary definitions of popular medical terms Visual acuity refers to the clarity or clearness of the vision, a measure of how well a person sees. Visual acuity test definition - Medical Dictionary definitions of popular medical terms Visual acuity test: This test measures how well you see at various distances. www.medterms.com /script/main/art.asp?articlekey=8549   (276 words)

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