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Optotypes
__NOTOC__ An eye chart is a chart used to measure visual acuity comprising lines of optotypes in ranges of sizes. Optotypes are the letters or symbols shown on an eye chart. Eye charts are often used by health care professionals, such as optometrists, physicians and nurses, to screen persons for vision impairment. Ophthalmologists, physicians who specialize in the eye, also use eye charts to monitor the visual acuity of their patients in response to various therapies such as medications or surgery. The chart is placed at a standardized distance away from the person whose vision is being tested. The person then attempts to identify the optotypes on the chart, starting with the larger ones and continuing with progressively smaller ones until the person cannot identify the optotypes. The size of the smallest optotypes that can be reliably identified is considered the person's visual acuity. The Snellen chart is the most widely used. Alternative types of eye charts include the logMAR ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snellen Chart
A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula developed by his professor Franciscus_Donders, Franciscus Cornelius Donders. Many ophthalmologists and vision scientists now use an improved chart known as the LogMAR chart. History Snellen developed charts using symbols based in a 5×5 unit grid. The experimental charts developed in 1861 used abstract symbols. Snellen's charts published in 1862 used alphanumeric capitals in the 5×5 grid. The original chart shows A, C, E, G, L, N, P, R, T, 5, V, Z, B, D, 4, F, H, K, O, S, 3, U, Y, A, C, E, G, L, 2. Description The normal Snellen chart is printed with eleven lines of block letters. The first line consists of one very large letter, which may be one of several letters, for example E, H, or N. Subsequent rows have increasing numbers of letters that decrease in s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lea Test
The LEA Vision Test System is a series of pediatric vision tests designed specifically for children who do not know how to read the letters of the alphabet that are typically used in eye charts. There are numerous variants of the LEA test which can be used to assess the visual capabilities of near vision and distance vision, as well as several other aspects of occupational health, such as contrast sensitivity, visual field, color vision, visual adaptation, motion perception Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs. Although this process appears straightforward to most observers, it has proven to be a difficul ..., and ocular function and accommodation (eye). History The first version of the LEA test was developed in 1976 by Finnish pediatric ophthalmologist Lea Hyvärinen, MD, PhD. Dr. Hyvärinen completed her thesis on fluorescein angiography and helped start the first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LogMAR Chart
A logMAR chart is a chart consisting of rows of letters that is used by ophthalmologists, orthoptists, optometrists, and vision scientists to estimate visual acuity. The name of the chart is an abbreviation for "logarithm of the Minimum Angle of Resolution". The chart was developed at the National Vision Research Institute of Australia in 1976, and is designed to enable a more accurate estimate of acuity than do other charts (e.g., the Snellen chart).Bailey IL, Lovie JE. I (1976.) ''New design principles for visual acuity letter charts''. Am J Optom Physiol Opt. 53 (11): pp. 740–745. For this reason, the LogMAR chart is recommended, particularly in a research setting. When using a LogMAR chart, visual acuity is scored with reference to the logarithm of the minimum angle of resolution, as the chart's name suggests. An observer who can resolve details as small as 1 minute of visual angle scores LogMAR 0, since the base-10 logarithm of 1 is 0; an observer who can resolve de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Acuity
Visual acuity (VA) commonly refers to the clarity of visual perception, vision, but technically rates an animal's ability to recognize small details with precision. Visual acuity depends on optical and neural factors. Optical factors of the eye influence the sharpness of an image on its retina. Neural factors include the health and functioning of the retina, of the neural pathways to the brain, and of the interpretative faculty of the brain. The most commonly referred-to visual acuity is ''distance acuity'' or ''far acuity'' (e.g., "20/20 vision"), which describes someone's ability to recognize small details at a far distance. This ability is compromised in people with myopia, also known as short-sightedness or near-sightedness. Another visual acuity is ''Near visual acuity, near acuity'', which describes someone's ability to recognize small details at a near distance. This ability is compromised in people with hyperopia, also known as long-sightedness or far-sightedness. A com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landolt C
The Landolt C, also known as a Landolt ring, Landolt broken ring, or Japanese vision test, is an optotype—a standardized symbol used for testing vision. It was developed by the Swiss-born ophthalmologist Edmund Landolt. The Landolt C consists of a ring that has a gap, thus looking similar to the letter C. The gap can be at various positions (usually left, right, bottom, top and the 45° positions in between) and the task of the tested person is to decide on which side the gap is. The size of the C and its gap are reduced until the subject makes a specified rate of errors. The minimum perceivable angle of the gap is taken as measure of the visual acuity. It is generally practised in the laboratory. The stroke width is of the diameter, and the gap width is the same. This is identical to the letter C from a Snellen chart. The Landolt C is the standard optotype for acuity measurement in most European countries. It was standardized, together with measurement procedures, by the G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jaeger Chart
The Jaeger chart is an eye chart used in testing near visual acuity. It is a card on which paragraphs of text are printed, with the text sizes increasing from 0.37 mm to 2.5 mm. This card is to be held by a patient at a fixed distance from the eye dependent on the J size being read. The smallest print that the patient can read determines their visual acuity. The original 1867 chart had a text containing seven paragraphs and a corresponding seven-point scale. Jaeger cards are not standardized, and the variability of the actual size of test letters on different Jaeger cards currently in use is very high. Therefore, test results with different Jaeger cards are not comparable. More commonly, distance vision acuity is tested using the Snellen chart A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula developed by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
E Chart
An E chart, also known as a tumbling E chart, is an eye chart used to measure a patient's visual acuity. Uses This chart does not depend on a patient's easy familiarity with a particular writing system (such as the Latin alphabet). This is often desirable, for instance with very young children. This also allows use with patients not readily fluent in the alphabetfor example, in China. The chart contains rows of the letter "E" in various kinds of rotation. The patient is asked to state (usually by pointing) where the limbs of the E are pointing, "up, down, left or right." Depending on how far the patient can "read", their visual acuity is quantified. It works on the same principle as Snellen's distant vision chart. See also * Visual acuity Visual acuity (VA) commonly refers to the clarity of visual perception, vision, but technically rates an animal's ability to recognize small details with precision. Visual acuity depends on optical and neural factors. Optical factors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herman Snellen
Herman Snellen (, February 19, 1834 – January 18, 1908) was a Dutch ophthalmologist who in 1862 introduced the Snellen chart to study visual acuity. He took over directorship of the Netherlands Hospital for Eye Patients (Nederlandsch Gasthuis voor Ooglijders), after Franciscus Donders. He was elected an International Member of the American Philosophical Society in 1894. Early life Herman Snellen studied medicine at Utrecht University under Donders, Gerardus Johannes Mulder and Jacobus Schroeder van der Kolk. He earned his medical degree in 1858 from Leiden University. He specialized in ophthalmology and worked as an assistant physician at the Netherlands Hospital for Eye Patients after he had completed his degree. Director He was named to succeed Donders as the institute's director in 1884, a position he served until 1903. In 1877, he was appointed as a professor of ophthalmology at Utrecht University. He did research on astigmatism, glaucoma and other eye diseases as well as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heinrich Küchler
Heinrich Georg Küchler (23 April 1811, Darmstadt – 29 March 1873, Darmstadt) was a German ophthalmologist. From 1828 he studied medicine at the University of Giessen, and after graduation visited Paris for study. In 1834 he returned to Darmstadt, where he started a private ophthalmic practice. In 1836 he was arrested unexpectedly because of his actions in association with a ''Burschenschaft'' (fraternal organization) at Giessen. For nearly three years he was imprisoned, obtaining his freedom in January 1839. After his release, he resumed his ophthalmic practice in Darmstadt.ADB:Küchler, Heinrich – Wikisource at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eduard Jäger Von Jaxtthal
Eduard Jäger von Jaxtthal (25 June 1818 in Vienna – 5 July 1884 in Vienna) was an Austrian ophthalmologist who was a native of Vienna. He was a professor at the University of Vienna, and was son to oculist Friedrich Jäger von Jaxtthal (1784-1871), and grandson to Georg Joseph Beer (1763-1821). Jäger is remembered for his work involving eye operations, and for his research of ophthalmic disorders. He was an early practitioner of the ophthalmoscope, and was among the first to use ophthalmoscopy to determine refractive error in the eye. Also, he is credited with providing the first description of retinal appearances associated with diabetes. In the 1850s Jäger made improvements to eye chart test types that were earlier developed by Heinrich Küchler (1811-1873). In 1862 Dutch ophthalmologist Hermann Snellen introduced the popular "Snellen chart" for testing visual acuity.H. Snellen, Probebuchstaben zur Bestimmung der Sehschärfe, Utrecht 1862. Selected writings * ''Bei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Perception
Visual perception is the ability to detect light and use it to form an image of the surrounding Biophysical environment, environment. Photodetection without image formation is classified as ''light sensing''. In most vertebrates, visual perception can be enabled by photopic vision (daytime vision) or scotopic vision (night vision), with most vertebrates having both. Visual perception detects light (photons) in the visible spectrum reflected by objects in the environment or emitted by light sources. The light, visible range of light is defined by what is readily perceptible to humans, though the visual perception of non-humans often extends beyond the visual spectrum. The resulting perception is also known as vision, sight, or eyesight (adjectives ''visual'', ''optical'', and ''ocular'', respectively). The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in linguistics, psychology, cognitive s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Utrecht
Utrecht ( ; ; ) is the List of cities in the Netherlands by province, fourth-largest city of the Netherlands, as well as the capital and the most populous city of the Provinces of the Netherlands, province of Utrecht (province), Utrecht. The municipality of Utrecht is located in the eastern part of the Randstad conurbation, in the very centre of mainland Netherlands, and includes Haarzuilens, Vleuten and De Meern. It has a population of 376,435 as of . Utrecht's ancient city centre features many buildings and structures, several dating as far back as the High Middle Ages. It has been the religious centre of the Netherlands since the 8th century. In 1579, the Union of Utrecht was signed in the city to lay the foundations for the Dutch Republic. Utrecht was the most important city in the Netherlands until the Dutch Golden Age, when it was surpassed by Amsterdam as the country's cultural centre and most populous city. Utrecht is home to Utrecht University, the largest university ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
