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Topic: Visual acuity

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	LaserMyEye :: Encyclopedia :: Visual acuity
		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.
		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.
	www.lasermyeye.org /encyclopedia/acuity.html (244 words)

	Visual acuity - Wikipedia, the free encyclopedia
		Visual cortex is part of the cerebral cortex in the posterior (occipital) part of the brain responsible for processing visual stimuli.
		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.
	en.wikipedia.org /wiki/Visual_acuity (2466 words)

	Visual Acuity -- Clinical Methods -- NCBI Bookshelf
		The presence of excellent visual acuity tells the examiner that the ocular media are clear, the image is clearly focused on the retina, the afferent visual pathway is functioning, and the visual cortex has appropriately interpreted signals received.
		The fundamental mechanisms of central visual loss are therefore twofold: (1) The optical properties of the eye are altered to cause loss or distortion of light on its path to the retina; and (2) the retina is diseased or the neural pathways or cortical reception is defective.
		As stated previously, when the visual acuity is found to be 20/20, a great deal of information is obtained: the eye is properly refracted, the ocular media are clear, the foveal region of the retina is functioning, the optic nerve and visual cortex are generally intact.
	www.ncbi.nlm.nih.gov /bookshelf/br.fcgi?book=cm&part=A3529 (1324 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.
		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.
		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).
	www.agingeye.net /visionbasics/healthyvision.php (1028 words)

	Activity 3A: Measuring Visual Acuity (Site not responding. Last check: )
		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 measure of visual acuity is the angle formed between the eye and the letter.
		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.
	teachhealthk-12.uthscsa.edu /pa/pa06/0603A.htm (359 words)

	Visual Acuity
		Visual acuity often is referred to as “Snellen” acuity.
		One’s visual acuity is an indication of the clarity or clearness of one’s vision.
		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.
	www.tedmontgomery.com /the_eye/acuity.html (1462 words)

	Encyclopedia - Visual Acuity
		Visual acuity is the medical term for sharpness of vision.
		Myopia is a reduced ability to see distant objects clearly, hyperopia is a condition that initially causes difficulty in seeing nearby objects and progresses to affect distance vision, and astigmatism is blurred vision caused by abnormal curvature of the front surface of the cornea.
		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.
	www.visionrx.com /library/enc/enc_acuity.asp (376 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)

	BESB: Common Eye Conditions Which Lead To Low Vision
		Children born pre-1985, however, are often left with a visual acuity of 20/200 or worse due to the lack of modern techniques.
		Signs are varying vision, decrease in visual acuity, decrease in visual fields, diplopia, inability to accommodate, loss of color vision, refractive errors, hemorrhage of blood vessels in the retina, and retinal detachment.
		There is a decrease in visual acuity, severe myopia, scaring of the retina; often there is retinal detachment with loss of visual fields and complete visual loss.
	www.ct.gov /besb/cwp/view.asp?a=2849&q=331478 (2465 words)

	LaserMyEye :: Encyclopedia :: Uncorrected visual acuity (UCVA)
		Visual acuity score (20/X variety) without the aid of glasses or contact lenses.
		There are two different measures of visual acuity: uncorrected (without glasses) and "best-corrected" (your score when wearing the best prescription for you).
		It is entirely possible (and in laser eye surgery regularly occurs) that you can have excellent (20/20 or better) uncorrected visual acuity but not be happy with your vision because of vision quality problems that surgery has caused, such as poor night vision or double vision.
	www.lasermyeye.org /encyclopedia/ucva.html (232 words)

	[No title]
		Visual acuity tests using optotypes are linear tests, single symbol tests, or tests with crowded symbols.
		Therefore the testing of visual acuity should be done at the preferred distance and with the preferred head posture.
		Communication during measurement of visual acuity in near vision is often problematic because the patients fingerspell the letters close to the test.
	www.lea-test.fi /en/deaf/part3/visual1.html (1291 words)

	2.00-Special Senses and Speech-Adult
		A cortical visual disorder is a disturbance of the posterior visual pathways or occipital lobes of the brain in which the visual system does not interpret what the eyes are seeing.
		We calculate the percent of visual efficiency by multiplying the visual acuity efficiency by the visual field efficiency and converting the decimal to a percentage.
		If your visual acuity is measured with one of these newer charts, and you cannot read any of the letters on the 20/100 line, we will determine that you have statutory blindness based on a visual acuity of 20/200 or less.
	www.ssa.gov /disability/professionals/bluebook/2.00-SpecialSensesandSpeech-Adult.htm (3221 words)

	Visual Acuity in Sensory Substitution for the Blind
		In other words, in measuring visual acuity of a vision substitution device, it should in principle not be allowed to manually sweep the camera.
		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.
		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.
	www.seeingwithsound.com /acuity.htm (2409 words)

	Webvision: Spatial Resolution
		Visual acuity is limited by diffraction, aberrations and photoreceptor density in the eye (Smith and Atchison, 1997).
		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).
		Visual acuity measurement in the clinic use high contrast, that is, fl letters on a white background.
	webvision.med.utah.edu /KallSpatial.html (4199 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)

	VA
		Using the patient’s visual acuity, accompanied with other testing, is necessary to determine the appropriate spectacle or contact lens prescription for the individual as well as give the physician insight into the health and integrity of the patient’s eye.
		Visual Acuity is the "resolving power" of the eye; that is, the smallest degree to which an individual can see a defined image.
		This measure of visual acuity is very similar to the Landholt C visual acuity testing as it relies on "form sense" for evaluation of minimum cognizable/minimum legible acuity.
	www.nova.edu /hpd/otm/otm-a/guestlects/visual_acuity.htm (2338 words)

	102.00-SpecialSensesandSpeech-Childhood
		Visual disorders are abnormalities of the eye, the optic nerve, the optic tracts, or the brain that may cause a loss of visual acuity or visual fields.
		If your visual disorder has progressed to the point at which it is likely to result in a significant limitation in the central visual field, such as a scotoma (see 102.00A8c), we will not use automated kinetic perimetry to evaluate your visual field loss.
		For example, if your visual acuity efficiency is 75 percent and your visual field efficiency is 64 percent, we will multiply 0.75 × 0.64 to determine that your visual efficiency is 0.48, or 48 percent.
	www.ssa.gov /disability/professionals/bluebook/102.00-SpecialSensesandSpeech-Childhood.htm (3177 words)

	Lesson 3: Measuring Visual Acuity (Site not responding. Last check: )
		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)

	Apparatus for visual acuity test - Patent 5416540
		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.
		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.
	www.freepatentsonline.com /5416540.html (3081 words)

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

	A New Perspective - Visual Acuity (Site not responding. Last check: )
		Visual acuity is the clarity or sharpness of the image that someone sees.
		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
		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)

	What is Visual Acuity?
		Visual acuity is defined as the clarity or sharpness of vision, which is the ability of the eye to see and distinguish fine details.
		Visual acuity is also affected by conditions such as shortsightedness and long sightedness.
		Good visual acuity is required for employment in certain occupations, such as airline pilot or police officer.
	www.wisegeek.com /what-is-visual-acuity.htm (386 words)

	[Clinical Preventive Services] Screening for Visual Impairment (Site not responding. Last check: )
		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.
		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.
		Impaired visual acuity is readily detected by use of a Snellen chart.
	cpmcnet.columbia.edu /texts/gcps/gcps0043.html (2578 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.
		To quantify losses in visual acuity during head movement, the first step is to determine the patient's head fixed (static) visual acuity.
		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.
	www.onbalance.com /neurocom/protocols/VORImpairment/dva.aspx (637 words)

	Visual Acuity
		Visual acuity is measured with visual acuity charts.
		If he can read just the top letter, his visual acuity is 6/60 or 20/200.If he can read, the second line, it is 6/36 or 20/100 and so on.
		Refraction is done and Visual acuity is retested with corrective glasses and recorded as vision with glasses correction.
	members.tripod.com /manisha_b/Eye_Exams/Visual_Acuity_Charts.htm (273 words)

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