Visual impairment (or vision impairment) is vision loss Vision loss or visual loss is the absence of vision where it existed before, which can happen either acutely or chronically (i.e. over a long period of time) (of a person) to such a degree as to qualify as a handicap through a significant limitation of visual Visual perception is the ability to interpret information and surroundings from visible light reaching the eye. The resulting perception is also known as eyesight, sight or vision. The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in psychology, cognitive capability resulting from either disease A disease or medical condition is an abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune diseases, trauma Physical trauma refers to a physical injury, generally of a considerably severe degree. A trauma patient is someone who has suffered serious and life-threatening physical injury with the potential for secondary complications such as shock, respiratory failure and death, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction, medication, or surgery.[1][2][3] This functional loss of vision is typically defined to manifest with
- best corrected visual acuity Visual acuity is acuteness or clearness of vision, especially form vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain of less than 20/60, or significant central field defect,
- significant peripheral field defect including homonymous or heteronymous bilateral visual, field defect or generalized contraction or constriction of field, or
- reduced peak contrast sensitivity with either of the above conditions.[1][2][3]
In the United States The United States of America is a federal constitutional republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the,[5] the terms "partially sighted," "low vision Low vision is a subspecialty within the professions of optometry and ophthalmology and opticianry dealing with individuals who have less than normal vision even with the most accurate conventional prescription available. It can be a result of either congenital or acquired factors. An example of the former is Leber's congenital amaurosis and of the," "legally blind," and "totally blind Blindness is the condition of lacking visual perception due to physiological or neurological factors" are used in the educational context to describe students with visual impairments. They are defined as follows:
- Partially sighted indicates some type of visual problem, with a need of person to receive special education in some cases;
- Low vision generally refers to a severe visual impairment, not necessarily limited to distance vision. Low vision applies to all individuals with sight who are unable to read the newspaper at a normal viewing distance, even with the aid of eyeglasses or contact lenses. They use a combination of vision and other senses to learn, although they may require adaptations in lighting or the size of print, and, sometimes, Braille The Braille system is a method that is widely used by blind people to read and write. Braille was devised in 1821 by Louis Braille, a blind Frenchman. Each Braille character or cell is made up of six dot positions, arranged in a rectangle containing two columns of three dots each. A dot may be raised at any of the six positions to form sixty-four;
- Myopic Myopia , also called nearsightedness or shortsightedness, is a refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed - unable to see distant objects clearly, commonly called near-sighted or short-sighted
- Hyperopic Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance. As an object moves toward the eye, the eye must increase its power to keep the - unable to see close objects clearly, commonly called far-sighted or long-sighted
- Legally blind indicates that a person has less than 20/200 vision in the better eye after best correction (contact lenses or glasses), or a field of vision of less than 20 degrees in the better eye; and
- Totally blind students learn via Braille or other non-visual media.
Visual impairment is the consequence of a functional loss of vision, rather than the eye disorder itself. Eye disorders which can lead to visual impairments can include retinal The vertebrate retina is a light sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These degeneration, albinism Albinism is a form of hypopigmentary congenital disorder, characterized by a partial lack (in hypomelanism, also known as hypomelanosis) or total absence (amelanism or amelanosis) of melanin pigment in the eyes, skin and hair, or more rarely in the eyes alone. Albinism results from inheritance of recessive gene alleles. The condition is known to, cataracts A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light. Early in the development of age-related cataract the power of the lens may be increased, causing near-sightedness , and the gradual yellowing and opacification of the, glaucoma Glaucoma is a disease that affects the optic nerve and involves loss of retinal ganglion cells in a characteristic pattern. There are many different sub-types of glaucoma but they can all be considered as a type of optic neuropathy. Raised intraocular pressure is a significant risk factor for developing glaucoma . One person may develop nerve, muscular problems that result in visual disturbances, corneal The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. While the cornea contributes most of the eye' disorders, diabetic retinopathy Diabetic retinopathy is retinopathy caused by complications of diabetes mellitus, which can eventually lead to blindness. It is an ocular manifestation of systemic disease which affects up to 80% of all patients who have had diabetes for 10 years or more. Despite these intimidating statistics, research indicates that at least 90% of these new, congenital disorders Congenital disorder involves defects in or damage to a developing fetus. It may be the result of genetic abnormalities, the intrauterine environment, errors of morphogenesis, or a chromosomal abnormality. The outcome of the disorder will further depend on complex interactions between the pre-natal deficit and the post-natal environment. Congenital, and infection An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply, usually at the expense of the host. The infecting organism, or pathogen, interferes with the normal functioning of the host and can lead to chronic wounds, gangrene, loss." Visual impairment can also be caused by brain and nerve disorders, in which case it is usually termed cortical visual impairment (CVI).
The American Medical Association The American Medical Association , founded in 1847 and incorporated 1897, is the largest association of physicians and medical students in the United States. While its membership has declined in recent years, it claims approximately 20% of practicing physicians as members. The AMA's stated mission is to promote the art and science of medicine for's Guides to the Evaluation of Permanent Impairment attempts to provide "a standardized, objective approach to evaluating medical impairments." The Visual System chapter "provides criteria for evaluating permanent impairment of the visual system as it affects an individual's ability to perform activities of daily living."[6] The Guide has estimated that the loss of one eye equals 25% impairment of the visual system and 24% impairment of the whole person;[6][7] total loss of vision in both eyes is considered to be 100% visual impairment and 85% impairment of the whole person.[6]
Visual impairments have considerable economic impact on even developed countries.[8]
Visual impairment is one of the potential dangers Ultraviolet germicidal irradiation is a sterilization method that uses ultraviolet (UV) light at sufficiently short wavelength to break down microorganisms. It is used in a variety of applications, such as food, air and water purification. UV has been a known mutagen at the cellular level for more than 100 years. The 1903 Nobel Prize for Medicine of ultraviolet germicidal irradiation Ultraviolet germicidal irradiation is a sterilization method that uses ultraviolet (UV) light at sufficiently short wavelength to break down microorganisms. It is used in a variety of applications, such as food, air and water purification. UV has been a known mutagen at the cellular level for more than 100 years. The 1903 Nobel Prize for Medicine.
See also
- Accessible image
- Maguire v SOCOG 2000 (Australian Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland (the world's smallest), the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans.N4 Neighbouring countries include Indonesia, East Timor, and Papua New Guinea to the north, the Solomon legal case about making a website accessible to a visually impaired person)
- GPS for the visually impaired
- Touch user interface
References
- ^ a b Arditi, A., & Rosenthal, B. (1998). "Developing an objective definition of visual impairment." In Vision '96: Proceedings of the International Low Vision Conference (pp. 331-334). Madrid, Spain: ONCE.
- ^ a b Medicare Vision Rehabilitation Services Act of 2003 HR 1902 IH
- ^ a b larrybelote.com
- ^ medem.com
- ^ National Dissemination Center for Children with Disabilities
- ^ a b c AMA Guides
- ^ Eye Trauma Epidemiology and Prevention
- ^ Taylor HR, Pezzullo ML, Keeffe JE. "The economic impact and cost of visual impairment in Australia." Br J Ophthalmol. 2006 Mar;90(3):272-5. PMID 16488942.
External links
- Low Vision Australia Low Vision Australia by Pacific Vision - information and product links
- http://www.direct.gov.uk/disability Directgov disabled people - UK govt information
- CDC’s National Center on Birth Defects and Developmental Disabilities
- World Health Organization site on blindness and visual impairment
- Eye Conditions (RNIB)
- LowVision.com Low Vision online informational resource center and referral hub
- Optelec US Visual impairment information and solutions
Categories: Disability | Ophthalmology Categories: Medical specialties | Surgical specialties | Eye | Vision
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ue, 17 Nov 2009 18:30:07 GM
It is also hoped that the Reader will level the playing field for the two million-plus people in the UK with . visual impairment. . The device can read data from up to 50cm away and size 10 font. But, while the Reader has gained the backing ...
