Buta
Dari Wikipedia bahasa Melayu
Buta adalah keadaan di mana kekurangan deria penglihatan kerana faktor fisiologi ataupun psychologi.
Pelbagai skala telahpun dimajukan bagi menggambarkan tahap kehilangan penglihatan dan mengtakrifkan "buta".[1] Buta sepenuhnya adalah kehilangan menyeluruh segala bentuk deria cahaya dan direkodkan secara perubatan (klinikal) sebagai "NLP", ringkatan kepada ("no light perception").[1] "Buta" seringkali digambarkan sebagai kecacatan penglihatan teruk dengan sisa penglihatan. Untuk menentukan mereka yang memerlukan bantuan khas disebabkan kecacatan penglihatan, pelbagai perundangan kerajaan telah membentuk takrifan yang semakin rumit yang dirujuk sebagai disahkan buta - (legal blindness).[2] Di Amerika Utara dan kebanyakan Eropah, disahkan buta ditakrifkan sebagai tahap penglihatan pada tahap 20/200 (6/60) atau kurang dari itu pada mata terbaik dengan pembetulan sebaik mungkin. Ini bererti individual yang disahkan buta. Ini bererti mereka yang disahkan buta perlu berdiri sejauh 20 kaki daripada sesuatu objek bagi melihatnya sejelas apa yang orang normal mampu lihat pada jarak 200 kaki. Pada kebanyakan kawasan, mereka dengan penglihatan tajam purata bagaimanapun mempunyai lapangan pandangan kurang daripada 20 sudut darjah (biasanya 180 darjah) juga dikelaskan sebagai disahkan buta.
Sekitar sepuluh peratus daripada mereka yang disahkan buta, menurut mana-mana ukuran, tidak mempunyai penglihatan. Bakinya mempunyai sedikit penglihatan, dari mengesan cahaya kepada ketajaman yang relatively good acuity. Low vision is sometimes used to describe visual acuities from 20/70 to 20/200. [1]
Menurut Penilaian semula ke 10 Pengkelasan Statistik Antarabangsa, Kecederaan dan Punca Kematian WHO, Penglihatan lemah ditakrifkan sebagai ketajamanpenglihatan kurang dari 6/18, tetapi lebih baik atau bersamaan dengan 3/60, atau bersamaan kehilangan medan penglihatan kepada kurang daripada 20 darjah, dalam mata terbaik dengan pembetulan terbaik. Buta ditakrifkan sebagai ketajaman penglihatan kurang dari 3/60, atau bersamaan kehilangan medan penglihatan kurang daripada 10 darjah, pada mata terbaik dengan pembetulan terbaik.[2][3]
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[Sunting] Buta Sah
Pada tahun 1934, Persatuan Perubatan Amerika menerima pakai istilah buta seperti berikut:
- "Ketajaman pandangan pusat pada 20/200 atau kurang pada mata terbaik dengan kanta pembetulan atau ketajaman pandangan pusat lebih dari 20/200 sekiranya terdapat kecacatan medan penglihatan di mana pandangan sisi kucup pada tahap di mana keratan rentas terlebar dari mana luas medan penglihatan tidak melebihi 20 darjah pada mata terbaik."[3]
Kongres Amerika Syarikat memasukkan takrifan ini sebagai sebahagian dari program Bantuan kepada orang buta dalam Akta Keselamatan Sosial yang diluluskan pada 1935[3][4]. Pada tahun 1972, program Bantuan kepada orang buta dan dua yang lain di gabung di bawah judul XVI bagi Akta Keselamatan Sosial untuk membentuk program Tambahan Keselamatan Pendapatan [4] yang kini menyatakan:
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- "Seseorang dianggap buta bagi tujuan gelaran ini sekiranya ia mempunyai ketajaman penglihatan pusat 20/200 20/200 atau kurang pada mata terbaik dengan kanta pembetulan. Mata yang diiringi dengan kecacatan pada medan penglihatan sehinggakan ukurlilit terluas bagi sudut penglihatan melebar pada sudut tidak melebihi 20 darjah akah dianggap bagi matlamat ayat pertama subseksyen ini sebagai mempunyai ketajaman penglihatan pusat 20/200 atau kurang. An individual shall also be considered to be blind for purposes of this title if he is blind as defined under a State plan approved under title X or XVI as in effect for October 1972 and received aid under such plan (on the basis of blindness) for December 1973, so long as he is continuously blind as so defined." [5]
Kuwait is one of many nations that share the same criteria for legal blindness[6].
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[Sunting] Epidemiology
In 1987, it was estimated that 598,000 people in the United States met the legal definition of blindness[7]. Of this number, 58% were over the age of 65[7]. In 1994-1995, 1.3 million Americans reported legal blindness[8].
In November 2004 article Magnitude and causes of visual impairment, the WHO estimated that in 2002 there were 161 million (about 2.6% of the world population) visually impaired people in the world, of whom 124 million (about 2%) had low vision and 37 million (about 0.6%) were blind. [9]
[Sunting] Causes of blindness
Serious visual impairment has a variety of causes:
[Sunting] Diseases
Most visual impairment is caused by disease and malnutrition. According to WHO estimates in 2002, the most common causes of blindness around the world are:
- cataracts (47.8%),
- glaucoma (12.3%),
- uveitis (10.2%)
- age-related macular degeneration (AMD) (8.7%),
- trachoma (3.6%),
- corneal opacity (5.1%), and
- diabetic retinopathy (4.8%), among other causes.
People in developing countries are significantly more likely to experience visual impairment as a consequence of treatable or preventable conditions than are their counterparts in the developed world. While vision impairment is most common in people over age 60 across all regions, children in poorer communities are more likely to be affected by blinding diseases than are their more affluent peers.
The link between poverty and treatable visual impairment is most obvious when conducting regional comparisons of cause. Most adult visual impairment in North America and Western Europe is related to age-related macular degeneration and diabetic retinopathy. While both of these conditions are subject to treatment, neither can be cured.
In developing countries, wherein people have shorter life expectancies, cataracts and water-borne parasites—both of which can be treated effectively—are most often the culprits (see River blindness, for example). Of the estimated 40 million blind people located around the world, 70–80% can have some or all of their sight restored through treatment.
In developed countries where parasitic diseases are less common and cataract surgery is more available, age-related macular degeneration, glaucoma, and diabetic retinopathy are usually the leading causes of blindness[10].
[Sunting] Abnormalities and injuries
Eye injuries, most often occurring in people under 30, are the leading cause of monocular blindness (vision loss in one eye) throughout the United States. Injuries and cataracts affect the eye itself, while abnormalities such as optic nerve hypoplasia affect the nerve bundle that sends signals from the eye to the back of the brain, which can lead to decreased visual acuity.
People with injuries to the occipital lobe of the brain can, despite having undamaged eyes and optic nerves, still be legally or totally blind.
[Sunting] Genetic defects
People with albinism often suffer from visual impairment to the extent that many are legally blind, though few of them actually cannot see. Leber's congenital amaurosis can cause total blindness or severe sight loss from birth or early childhood.
Recent advances in mapping the human genome have identified other genetic causes of low vision or blindness. One such example is Bardet-Biedl syndrome.
[Sunting] Poisoning
A small portion of all cases of blindness are caused by the intake of certain chemicals. A well-known example is methanol which is found in methylated spirits which is sometimes used by alcoholics as a cheap substitute for regular alcoholic beverages.
[Sunting] Willful actions
Blinding has been used as an act of vengeance and torture in some instances, to deprive a person of a major sense by which they can navigate or interact within the world, act fully independently, and be aware of events surrounding them.
[Sunting] Blindness prevention
There exist a number of organizations, such as International Agency for the Prevention of Blindness, ORBIS International, and Seva Foundation, who have developed programs aimed at preventing blindness.
[Sunting] Adaptive techniques
Visually impaired and blind people have devised a number of techniques that allow them to complete daily activities using their remaining senses. These might include the following:
- Adaptive computer software that allows people with visual impairments to interact with their computer via audio or screen magnifiers.
- Adaptations of banknotes so that the value can be determined by touch. For example:
- In some currencies, such as the euro, pound sterling and Australian dollar, the size of a note increases with its value.
- Many banknotes from around the world have a tactile feature to indicate denomination in the upper right corner. This tactile feature is a series of raised dots, but it is not standard Braille [5].
- It is also possible to fold notes in different ways to assist recognition.
- Labeling and tagging clothing and other personal items
- Placing different types of food at different positions on a dinner plate
- Marking controls of household appliances
Most people, once they have been visually impaired for long enough, devise their own adaptive strategies in all areas of personal and professional management.
For corrective surgery of blindness, see Acquired vision.
[Sunting] Tools
Designers, both visually impaired and sighted, have developed a number of tools for use by blind people.
[Sunting] Mobility
Many people with serious visual impairments can travel independently assisted by tactile paving and/or using a white cane, the international symbol of blindness.
A long cane is used to extend the user's range of touch sensation, swung in a low sweeping motion across the intended path of travel to detect obstacles. However, some visually impaired persons do not carry these kinds of canes, opting instead for the shorter, lighter identification (ID) cane. Still others require a support cane.
Each of these is painted white for maximum visibility, and to denote visual impairment on the part of the user. In addition to making rules about who can and cannot use a cane, some governments mandate the right-of-way be given to users of white canes or guide dogs.
A small number of people employ guide dogs. Although the dogs can be trained to navigate various obstacles, they are partially (red-green) color blind and are not capable of interpreting street signs. The human half of the guide dog team does the directing, based upon skills acquired through previous mobility training. The handler might be likened to an aircraft's navigator, who must know how to get from one place to another, and the dog is the pilot, who gets them there safely.
Many blind people will accept help, however, make sure that they are aware that you are going to help them, and offer your arm, not your whole body.
[Sunting] Reading and magnification
Most blind and visually impaired people read print, either of a regular size or enlarged through the use of magnification devices. A variety of magnifying glasses, some of which are handheld, and some of which rest on desktops, can make reading easier for those with decreased visual acuity.
The rest read Braille and Moon type or rely on talking books and readers or reading machines. They use computers with special hardware such as scanners and refreshable Braille displays as well as software written specifically for the blind, like optical character recognition applications and screen reading software.
Some people access these materials through agencies for the blind, such as the National Library Service for the Blind and Physically Handicapped in the United States, the National Library for the Blind or the RNIB in the United Kingdom.
Closed-circuit televisions, equipment that enlarges and contrasts textual items, are a more high-tech alternative to traditional magnification devices. So too are modern web browsers, which can increase the size of text on some web pages through browser controls or through user-controlled style sheets.
[Sunting] Computers
Access technology such as Freedom Scientific's JAWS for Windows screen reading software enable the blind to use mainstream computer applications. Most legally blind people (70% of them across all ages, according to the Seattle Lighthouse for the Blind) do not use computers. Only a small fraction of this population, when compared to the sighted community, have Internet access. This bleak outlook is changing, however, as availability of assistive technology increases, accompanied by concerted efforts to ensure the accessibility of information technology to all potential users, including the blind. Linux distributions (as Live CDs) for the blind include Oralux and Adriane Knoppix, the latter developed in part by Adriane Knopper who has a visual impairment.
The movement towards greater web accessibility is opening a far wider number of websites to adaptive technology, making the web a more inviting place for visually impaired surfers.
Experimental approaches in sensory substitution are beginning to provide access to arbitrary live views from a camera.
[Sunting] Other aids
People may use talking thermometers, enlarged or marked oven dials, talking watches, talking clocks, talking scales, talking calculators, talking compasses and other talking equipment.
[Sunting] Social attitudes towards blindness
The story of the Blind Men and an Elephant uses blindness as a symbol of limited perception and perspective. Stories such as The Cricket on the Hearth by Charles Dickens provided yet another view of blindness, wherein those affected by it were ignorant of their surroundings and easily deceived.
The authors of modern educational materials (see: blindness and education for further reading on that subject), as well as those treating blindness in literature, have worked to paint a different picture of blind people as three-dimensional individuals with a range of abilities, talents, and even character flaws.
[Sunting] Pautan luar
- Pemantau Capaian: Pengguna buta menilai kebolehgunaan aturcara utama.
- Majlis Orang-orang Buta Amerika (American Council of the Blind)
- Yayasan Orang-orang Buta Amerika (American Foundation for the Blind)
- Blind Access Journal (Journal Capaian Orang-orang Buta): Kecacatan penglihatan dalam dunia sebenar
- Christian Blind Mission
- VISION 2020: Hak Untuk Melihat
- International Agency for the Prevention of Blindness (IAPB)
- Pusat Penyelidikan Braille Antarabangsa
- Literature Bibliography and Resources List
- National Braille Press
- National Federation of the Blind: Civil rights and consumer advocacy
- National Library for the Blind
- National Library Service for the Blind and Physically Handicapped
- Recording for the Blind and Dyslexic
- Royal National Institute for the Blind
- Scottish Sensory Centre
- SMCCB Vision Links
- WHO Fact Sheet on Visual Impairment
