|
High-energy Visible Light
High-energy visible light (HEV light) is high-frequency, high-energy light in the violet/blue band from 400 to 450 nm in the visible spectrum, which has a number of biological effects, including those on the eye. HEV light may be a cause of age-related macular degeneration. Some sunglasses and beauty creams specifically block HEV, for added marketing value. Currently, a 2019 report by France's Agency for Food, Environmental and Occupational Health & Safety (ANSES) supports the 2010 result on the adverse effect of blue LED light (400-450 nm spike) on the eye, which can lead to impaired vision. It highlights short-term effects on the retina linked to intense exposure to blue LED light, and long-term effects linked to the onset of age-related macular degeneration. Although few studies have examined occupational causes of macular degeneration, they show that long-term sunlight exposure, specifically its blue-light component, is associated with macular degeneration in outdo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photon Energy
Photon energy is the energy carried by a single photon. The amount of energy is directly proportional to the photon's electromagnetic frequency and thus, equivalently, is inversely proportional to the wavelength. The higher the photon's frequency, the higher its energy. Equivalently, the longer the photon's wavelength, the lower its energy. Photon energy can be expressed using any unit of energy. Among the units commonly used to denote photon energy are the electronvolt (eV) and the joule (as well as its multiples, such as the microjoule). As one joule equals 6.24 × 1018 eV, the larger units may be more useful in denoting the energy of photons with higher frequency and higher energy, such as gamma rays, as opposed to lower energy photons as in the optical and radio frequency regions of the electromagnetic spectrum. Formulas Physics Photon energy is directly proportional to frequency. E = hf where *E is energy *h is the Planck constant * f is frequency This equation is known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Sense Media
Common Sense Media (CSM) is an organization that reviews and provides ratings for media and technology with the goal of providing information on their suitability for children. , ''NYT'', May 5, 2003. Accessed Dec 15, 2011. It also funds research on the role of media in the lives of children and advocates publicly for child-friendly policies and laws regarding media. Founded by in 2003, Common Sense Media reviews (And allows users to do the same, divided into adult and child sections) s, movies, streaming/ |
Eye Strain
Eye strain, also known as asthenopia (from Greek ''a-sthen-opia'', grc, ἀσθενωπία, ), is a common eye condition that manifests through non-specific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional double vision. Symptoms often occur after long-term use of computers, digital devices, reading or other activities that involve extended visual tasks which are broadly classified into external and internal symptom factors. When concentrating on a visually intense task, such as continuously focusing on a book or computer monitor, the ciliary muscles and the extraocular muscles are strained. This causes discomfort, soreness or pain on the eyeballs. Closing the eyes for ten minutes and relaxing the muscles of the face and neck at least once an hour usually relieves the problem. A page or photograph with the same image twice, but slightly displaced (from a printing mishap, a camera moving during the shot, etc.) can cause eye strai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain ''complete subset'' of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a certain output device. Another sense, less frequently used but still correct, refers to the complete set of colors found within an image at a given time. In this context, digitizing a photograph, converting a digitized image to a different color space, or outputting it to a given medium using a certain output device generally alters its gamut, in the sense that some of the colors in the original are lost in the process. Introduction The term ''gamut'' was adopted from the field of music, where in middle age Latin "gamut" meant the entire range of musical notes of which musical melodies are composed; Shakespeare's use of the term in ''The Taming of the Shrew'' is sometimes attributed to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advertising Standards Authority (United Kingdom)
The Advertising Standards Authority (ASA) is the self-regulatory organisation of the advertising industry in the United Kingdom. The ASA is a non-statutory organisation and so cannot interpret or enforce legislation. However, its code of advertising practice broadly reflects legislation in many instances. The ASA is not funded by the British government, but by a levy on the advertising industry. Its role is to "regulate the content of advertisements, sales promotions and direct marketing in the UK" by investigating "complaints made about ads, sales promotions or direct marketing", and deciding whether such advertising complies with its advertising standards codes. These codes stipulate that "before distributing or submitting a marketing communication for publication, marketers must hold documentary evidence to prove all claims, whether direct or implied, that are capable of objective substantiation" and that "no marketing communication should mislead, or be likely to mislead, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boots Opticians
Boots Opticians Ltd. operates a chain of ophthalmic and dispensing optician stores in the United Kingdom. The company is a subsidiary of Walgreens Boots Alliance (58%) and De Rigo (42%). History The company began trading in the British optical retail market in 1983 in Nottingham, before opening practices in Peterborough, Leeds, Mansfield, Luton and Derby in 1984. Boots Opticians Ltd was formed as a subsidiary of Boots The Chemists Ltd in 1987, with the acquisition of Clement Clarke Ltd. and Curry and Paxton Ltd. All of Boots Opticians' laser eye surgeries were bought by Optical Express in late 2004. On 29 January 2009, it was announced that Boots Opticians were to merge with Dollond & Aitchison, forming a chain of 690 stores and 5,000 staff after Boots purchased a controlling share in D&A. In May 2019, the company was reported to be considering closing more than 200 stores within two years. there were around 630 stores, 180 of them operated by franchisees. Amid falling sale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
General Optical Council
The General Optical Council (GOC) is an organisation in the United Kingdom which maintains a register of opticians and regulates the services provided by dispensing opticians and optometrists. The stated function of the GOC is "''to protect the public and promote high standards of professional conduct and education amongst opticians''". Role In order to practice as optometrist or work as a dispensing optician within the UK, individuals must demonstrate to the GOC that they are suitably qualified and fit to practise. The GOC also maintains a register of companies who carry on business as opticians. , the register had around 30,000 optometrists, dispensing opticians, undergraduate optometry students, opticians and optical businesses. The GOC sets standards so that every registered practitioner knows what is expected of them. They take action against opticians who do not meet these standards of professional conduct and also against people or companies who break the terms of the Opt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sunlight
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When blocked by clouds or reflected off other objects, sunlight is diffused. Sources estimate a global average of between 164 watts to 340 watts per square meter over a 24-hour day; this figure is estimated by NASA to be about a quarter of Earth's average total solar irradiance. The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a requisite for vitamin D3 synthesis and a mutagen. Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. A photon starting at the center of the Sun and changing direction eve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Luminosity Function
A luminous efficiency function or luminosity function represents the average spectral sensitivity of human visual perception of light. It is based on subjective judgements of which of a pair of different-colored lights is brighter, to describe relative sensitivity to light of different wavelengths. It is not an absolute reference to any particular individual, but is a standard observer representation of visual sensitivity of theoretical human eye. It is valuable as a baseline for experimental purposes, and in colorimetry. Different luminous efficiency functions apply under different lighting conditions, varying from photopic in brightly lit conditions through mesopic to scotopic under low lighting conditions. When not specified, ''the luminous efficiency function'' generally refers to the photopic luminous efficiency function. The CIE photopic luminous efficiency function or is a standard function established by the Commission Internationale de l'Éclairage (CIE) and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Commission On Illumination
The International Commission on Illumination (usually abbreviated CIE for its French name, Commission internationale de l'éclairage) is the international authority on light, illumination, colour, and colour spaces. It was established in 1913 as a successor to the Commission Internationale de Photométrie, which was founded in 1900, and is today based in Vienna, Austria. Organization The CIE has six active divisions, each of which establishes technical committees to carry out its program: * Division 1: Vision and Colour * Division 2: Physical Measurement of Light and Radiation * Division 3: Interior Environment and Lighting Design * Division 4: Transportation and Exterior Applications * Division 6: Photobiology and Photochemistry * Division 8: Image Technology Two divisions are no longer active: * Division 5: Exterior Lighting and Other Applications * Division 7: General Aspects of Lighting The President of the CIE from 2019 is Dr Peter Blattner from Switzerland. CIE publi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Cycle
The visual cycle is a process in the retina that replenishes the molecule retinal for its use in vision. Retinal is the chromophore of most visual opsins, meaning it captures the photons to begin the phototransduction cascade. When the proton is absorbed, the ''11-cis retinal'' photoisomerizes into ''all-trans retinal'' as it is ejected from the opsin protein. Each molecule of retinal must travel from the photoreceptor cell to the RPE and back in order to be refreshed and combined with another opsin. This closed enzymatic pathway of ''11-cis retinal'' is sometimes called Wald's visual cycle after George Wald (1906–1997), who received the Nobel Prize in 1967 for his work towards its discovery. Retinal Retinal is a chromophore that forms photosensitive Retinylidene proteins when covalently bound to proteins called opsins. Retinal can be photoisomerized by itself, but requires to be bound to an opsin protein to both trigger the phototransduction cascade and tune the spectral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoreceptor Cell
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential. There are currently three known types of photoreceptor cells in mammalian eyes: rods, cones, and intrinsically photosensitive retinal ganglion cells. The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system to form an image of the environment, sight. Rods primarily mediate scotopic vision (dim conditions) whereas cones primarily mediate to photopic vision (bright conditions), but the processes in each that supports phototransduction is similar. A third class of mammalian photoreceptor cell was discovered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.svg "Click for more on -> High-energy Visible Light")
