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Visual impairment Braille
Visual impairment, also known as vision impairment or vision loss, is a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses. Some also include those who have a decreased ability to see because they do not have access to glasses or contact lenses. Visual impairment is often defined as a best corrected visual acuity of worse than either 20/40 or 20/60. The term blindness is used for complete or nearly complete vision loss. Visual impairment may cause people difficulties with normal daily activities such as driving, reading, socializing, and walking.

The most common causes of visual impairment globally are uncorrected refractive errors (43%), cataracts (33%), and glaucoma (2%). Refractive errors include near sighted, far sighted, presbyopia, and astigmatism. Cataracts are the most common cause of blindness. Other disorders that may cause visual problems include age related macular degeneration, diabetic retinopathy, corneal clouding, childhood blindness, and a number of infections. Visual impairment can also be caused by problems in the brain due to stroke, prematurity, or trauma among others. These cases are known as cortical visual impairment. Screening for vision problems in children may improve future vision and educational achievement.  Screening adults without symptoms is of uncertain benefit. Diagnosis is by an eye exam.

The World Health Organization (WHO) estimates that 80% of visual impairment is either preventable or curable with treatment. This includes cataracts, the infections river blindness and trachoma, glaucoma, diabetic retinopathy, uncorrected refractive errors, and some cases of childhood blindness. Many people with significant visual impairment benefit from vision rehabilitation, changes in their environmental, and assistive devices.

As of 2012 there were 285 million people who were visually impaired of which 246 million had low vision and 39 million were blind. The majority of people with poor vision are in the developing world and are over the age of 50 years. Rates of visual impairment have decreased since the 1990s. Visual impairments have considerable economic costs both directly due to the cost of treatment and indirectly due to decreased ability to work. 

Classification

The definition of visual impairment is reduced vision not corrected by glasses or contact lenses. The World Health Organization uses the following classifications of visual impairment. When the vision in the better eye with best possible glasses correction is:

* 20/30 to 20/60 : is considered mild vision loss, or near-normal vision
* 20/70 to 20/160 : is considered moderate visual impairment, or moderate low vision
* 20/200 to 20/400 : is considered severe visual impairment, or severe low vision
* 20/500 to 20/1,000 : is considered profound visual impairment, or profound low vision
* More than 20/1,000 : is considered near-total visual impairment, or near total blindness
* No light perception : is considered total visual impairment, or total blindness

Blindness is defined by the World Health Organization as vision in a person's best eye with best correction of less than 20/500 or a visual field of less than 10 degrees. This definition was set in 1972, and there is ongoing discussion as to whether it should be altered to officially include uncorrected refractive errors.

United Kingdom

Severely sight impaired 
* Defined as having central visual acuity of less than 3/60 with normal fields of vision, or gross visual field restriction. 
* Unable to see at 3 metres what the normally sighted person sees at 60 m.

Sight impaired 
* Able to see at 3 m, but not at 6 m, what the normally sighted person sees at 60 m
* Less severe visual impairment is not captured by registration data, and its prevalence is difficult to quantify

Low vision 
* A visual acuity of less than 6/18 but greater than 3/60. 
* Not eligible to drive and may have difficulty recognising faces across a street, watching television, or choosing clean, unstained, co-ordinated clothing. 

In the UK, the Certificate of Vision Impairment (CVI) is used to certify patients as severely sight impaired or sight impaired.  The accompanying guidance for clinical staff states: "The National Assistance Act 1948 states that a person can be certified as severely sight impaired if they are "so blind as to be unable to perform any work for which eye sight is essential". The test is whether a person cannot do any work for which eyesight is essential, not just his or her normal job or one particular job." 

In practice, the definition depends on individuals' visual acuity and the extent to which their field of vision is restricted. The Department of Health identifies three groups of people who may be classified as severely visually impaired.
#Those below 3/60 (equivalent to 20/400 in US notation) Snellen (most people below 3/60 are severely sight impaired).
#Those better than 3/60 but below 6/60 Snellen (people who have a very contracted field of vision only).
#Those 6/60 Snellen or above (people in this group who have a contracted field of vision especially if the contraction is in the lower part of the field).

The Department of Health also state that a person is more likely to be classified as severely visually impaired if their eyesight has failed recently or if they are an older individual, both groups being perceived as less able to adapt to their vision loss.

United States

In the United States, any person with vision that cannot be corrected to better than 20/200 in the best eye, or who has 20 degrees (diameter) or less of visual field remaining, is considered legally blind or eligible for disability classification and possible inclusion in certain government sponsored programs.

In the United States, the terms partially sighted, low vision, legally blind and totally blind are used by schools, colleges, and other educational institutions 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.
**Myopic – unable to see distant objects clearly, commonly called near-sighted or short-sighted.
**Hyperopic – 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.
*Totally blind students learn via Braille or other non-visual media.

In 1934, the American Medical Association adopted the following definition of blindness:
Central visual acuity of 20/200 or less in the better eye with corrective glasses or central visual acuity of more than 20/200 if there is a visual field defect in which the peripheral field is contracted to such an extent that the widest diameter of the visual field subtends an angular distance no greater than 20 degrees in the better eye. 

The United States Congress included this definition as part of the Aid to the Blind program in the Social Security Act passed in 1935.  In 1972, the Aid to the Blind program and two others combined under Title XVI of the Social Security Act to form the Supplemental Security Income program  which states:
An individual shall be considered to be blind for purposes of this title if he has central visual acuity of 20/200 or less in the better eye with the use of a correcting lens. An eye which is accompanied by a limitation in the fields of vision such that the widest diameter of the visual field subtends an angle no greater than 20 degrees shall be considered for purposes of the first sentence of this subsection as having a central visual acuity of 20/200 or less. 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. 

Other

Kuwait is one of many nations that share the 6/60 criteria for legal blindness. 

Health effects

Visual impairments may take many forms and be of varying degrees. Visual acuity alone is not always a good predictor of the degree of problems a person may have. Someone with relatively good acuity (e.g., 20/40) can have difficulty with daily functioning, while someone with worse acuity (e.g., 20/200) may function reasonably well if their visual demands are not great.

The American Medical Association has estimated that the loss of one eye equals 25% impairment of the visual system and 24% impairment of the whole person;  total loss of vision in both eyes is considered to be 100% visual impairment and 85% impairment of the whole person.

Some people who fall into this category can use their considerable residual vision – their remaining sight – to complete daily tasks without relying on alternative methods. The role of a low vision specialist (optometrist or ophthalmologist) is to maximize the functional level of a patient's vision by optical or non-optical means. Primarily, this is by use of magnification in the form of telescopic systems for distance vision and optical or electronic magnification for near tasks.

People with significantly reduced acuity may benefit from training conducted by individuals trained in the provision of technical aids. Low vision rehabilitation professionals, some of whom are connected to an agency for the blind, can provide advice on lighting and contrast to maximize remaining vision. These professionals also have access to non-visual aids, and can instruct patients in their uses.

The subjects making the most use of rehabilitation instruments, who lived alone, and preserved their own mobility and occupation were the least depressed, with the lowest risk of suicide and the highest level of social integration.

Those with worsening sight and the prognosis of eventual blindness are at comparatively high risk of suicide and thus may be in need of supportive services. These observations advocate the establishment and extension of therapeutic and preventative programs to include patients with impending and current severe visual impairment who do not qualify for services for the blind. Ophthalmologists should be made aware of these potential consequences and incorporate a place for mental health professionals in their treatment of these types of patients, with a view to preventing the onset of depressive symptomatology, avoiding self-destructive behavior, and improving the quality of life of these patients. Such intervention should occur in the early stages of diagnosis, particularly as many studies have demonstrated how rapid acceptance of the serious visual handicap has led to a better, more productive compliance with rehabilitation programs. Moreover, psychological distress has been reported (and is exemplified by our psychological autopsy study) to be at its highest when sight loss is not complete, but the prognosis is unfavorable.10 Therefore, early intervention is imperative for enabling successful psychological adjustment. 

Associated problems

Blindness can occur in combination with such conditions as intellectual disability, autism spectrum disorders, cerebral palsy, hearing impairments, and epilepsy.   Blindness in combination with hearing loss is known as deafblindness.

It has been estimated that over half of totally blind people have non-24-hour sleep–wake disorder, a condition in which a person's circadian rhythm, normally slightly longer than 24 hours, is not entrained (re-set) to the light/dark cycle.  

Cause

The most common causes of visual impairment globally in 2010 were:
#refractive errors (42%)
#cataracts (33%)
#glaucoma (2%)
#age related macular degeneration (1%)
#corneal opacification (1%)
#diabetic retinopathy (1%)
#childhood blindness
#trachoma (1%)
#undetermined (18%)

The most common causes of blindness in 2010 were:
#cataracts (51%)
#glaucoma (8%)
#age related macular degeneration (5%)
#corneal opacification (4%)
#childhood blindness (4%)
#refractive errors (3%)
#trachoma (3%)
#diabetic retinopathy (1%)
#undetermined (21%)

About 90% of people who are visually impaired live in the developing world. Age-related macular degeneration, glaucoma, and diabetic retinopathy are the leading causes of blindness in the developed world. 

Cataracts

Of these, cataract is responsible for >65%, or more than 22 million cases of blindness, and glaucoma is responsible for 6 million cases.

Cataracts: is the congenital and pediatric pathology that describes the greying or opacity of the crystalline lens, which is most commonly caused by intrauterine infections, metabolic disorders, and genetically transmitted syndromes.  Cataracts are the leading cause of child and adult blindness that doubles in prevalence with every ten years after the age of 40.  Consequently, today cataracts are more common among adults than in children. That is, people face higher chances of developing cataracts as they age. Nonetheless, cataracts tend to have a greater financial and emotional toll upon children as they must undergo expensive diagnosis, long term rehabilitation, and visual assistance.  Also, according to the Saudi Journal for Health Sciences, sometimes patients experience irreversible amblyopia after pediatric cataract surgery because the cataracts prevented the normal maturation of vision prior to operation.  Despite the great progress in treatment, cataracts remain a global problem in both economically developed and developing countries.  At present, with the variant outcomes as well as the unequal access to cataract surgery, the best way to reduce the risk of developing cataracts is to avoid smoking and extensive exposure to sun light (i.e. UV-B rays).

Glaucoma

Glaucoma is a congenital and pediatric eye disease characterized by increased pressure within the eye or intraocular pressure (IOP).Krader, Cheryl Guttman. "Etiology Determines IOP Treatment: Customized Approach Needed for Managing Elevated Pressure in Patients with Uveitis." Ophthalmology Times 15 May 2012: 24. Academic OneFile. Web. 5 Dec. 2013.. Glaucoma causes visual field loss as well as severs the optic nerve.Glaucoma Research Foundation. "High Eye Pressure and Glaucoma." Glaucoma Research Foundation. N.p., 5 Sept. 2013. Web.. Early diagnosis and treatment of glaucoma in patients is imperative because glaucoma is triggered by non-specific levels of IOP. Also, another challenge in accurately diagnosing glaucoma is that the disease has four etiologies: 1) inflammatory ocular hypertension syndrome (IOHS); 2) severe uveitic angle closure; 3) corticosteroid-induced; and 4) a heterogonous mechanism associated with structural change and chronic inflammation. In addition, often pediatric glaucoma differs greatly in etiology and management from the glaucoma developed by adults.Meszaros, Liz. "Pediatric, Adult Glaucoma Differ in Management: Patient Populations Not Same, so Diagnosis/clinical Approach Should Reflect Their Uniqueness." Ophthalmology Times 15 Sept. 2013: 11. Academic OneFile. Web. 5 Dec. 2013. . Currently, the best sign of pediatric glaucoma is an IOP of 21 mm Hg or greater present within a child. One of the most common causes of pediatric glaucoma is cataract removal surgery, which leads to an incidence rate of about 12.2% among infants and 58.7% among 10-year-olds.

Infections

Childhood blindness can be caused by conditions related to pregnancy, such as congenital rubella syndrome and retinopathy of prematurity. Leprosy and onchocerciasis each blind approximately 1 million individuals in the developing world.

The number of individuals blind from trachoma has decreased in the past 10 years from 6 million to 1.3 million, putting it in seventh place on the list of causes of blindness worldwide.

Central corneal ulceration is also a significant cause of monocular blindness worldwide, accounting for an estimated 850,000 cases of corneal blindness every year in the Indian subcontinent alone. As a result, corneal scarring from all causes is now the fourth greatest cause of global blindness. 

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.

Cortical blindness results from injuries to the occipital lobe of the brain that prevent the brain from correctly receiving or interpreting signals from the optic nerve. Symptoms of cortical blindness vary greatly across individuals and may be more severe in periods of exhaustion or stress. It is common for people with cortical blindness to have poorer vision later in the day.

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. An example from the classical realm is Oedipus, who gouges out his own eyes after realizing that he fulfilled the awful prophecy spoken of him. Having crushed the Bulgarians, the Byzantine Emperor Basil II blinded as many as 15,000 prisoners taken in the battle, before releasing them.  Contemporary examples include the addition of methods such as acid throwing as a form of disfigurement.

Genetic defects

People with albinism often have vision loss 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 of the human genome have identified other genetic causes of low vision or blindness. One such example is Bardet-Biedl syndrome.

Poisoning

Rarely, blindness is caused by the intake of certain chemicals. A well-known example is methanol, which is only mildly toxic and minimally intoxicating, and breaks down into the substances formaldehyde and formic acid which in turn can cause blindness, an array of other health complications, and death. When competing with ethanol for metabolism, ethanol is metabolized first, and the onset of toxicity is delayed. Methanol is commonly found in methylated spirits, denatured ethyl alcohol, to avoid paying taxes on selling ethanol intended for human consumption. Methylated spirits are sometimes used by alcoholics as a desperate and cheap substitute for regular ethanol alcoholic beverages.

Other

* Amblyopia: is a category of vision loss or visual impairment that is caused by factors unrelated to refractive errors or coexisting ocular diseases.  Amblyopia is the condition when a child's visual systems fail to mature normally because the child either suffers from a premature birth, measles, congenital nubella syndrome, vitamin A deficiency, or meningitis.  If left untreated during childhood, amblyopia is currently incurable in adulthood because surgical treatment effectiveness changes as a child matures. Consequently, amblyopia is the world's leading cause of child monocular vision loss, which is the damage or loss of vision in one eye. In the best case scenario, which is very rare, properly treated amblyopia patients can regain 20/40 acuity. 
* Corneal opacification
* Degenerative myopia
* Diabetic retinopathy: is one of the manifestation microvascular complications of diabetes, which is characterized by blindness or reduced acuity. That is, diabetic retinopathy describes the retinal and vitreous hemorrhages or retinal capillary blockage caused by the increase of A1C,  which a measurement of blood glucose or sugar level.American Diabetes Association. "A1c and Eag." Diabetes.org. N.p., 30 July 2013. Web. . In fact, as A1C increases, people tend to be at greater risk of developing diabetic retinopathy than developing other microvascular complications associated with diabetes (e.g. chronic hyperglycemia, diabetic neuropathy, and diabetic nephropathy). Despite the fact that only 8% of adults 40 years and older experience vision-threatening diabetic retinopathy (e.g. nonproliferative diabetic retinopathy or NPDR and proliferative diabetic retinopathy or PDR), this eye diseased accounted for 17% of cases of blindness in 2002.   
*Xerophthalmia, often due to vitamin A deficiency, is estimated to affect 5 million children each year; 500,000 develop active corneal involvement, and half of these go blind. 
*  Retinitis pigmentosa
*  Retinopathy of prematurity: The most common cause of blindness in infants worldwide. In its most severe form, ROP causes retinal detachment, with attendant visual loss. Treatment is aimed mainly at prevention, via laser or Avastin therapy.
* Stargardt's disease
* Uveitis: is a group of 30 intraocular inflammatory diseases  caused by infections, systemic diseases, organ-specific autoimmune processes, cancer or trauma.  That is, uveitis refers to a complex category of ocular diseases that can cause blindness if either left untreated or improperly diagnosed. The current challenge of accurately diagnosing uveitis is that often the cause or etiology of a specific ocular inflammation is either unknown or multi-layered. Consequently, about 3–10% uveitis victims in developed countries, and about 25% of victims in the developing countries, become blind from incorrect diagnosis and from ineffectual prescription of drugs, antibiotics or steroids. In addition, uveitis is a diverse category of eye diseases that are subdivided as granulomatous (or tumorous) or non-granulomatous anterior, intermediate, posterior or pan uveitis. In other words, uveitis diseases tend to be classified by their anatomic location in the eye (e.g. uveal tract, retina, or lens), as well as can create complication that can cause cataracts, glaucoma, retinal damage, age-related macular degeneration or diabetic retinopathy.

Diagnosis

It is important that people be examined by someone specializing in low vision care prior to other rehabilitation training to rule out potential medical or surgical correction for the problem and to establish a careful baseline refraction and prescription of both normal and low vision glasses and optical aids. Only a doctor is qualified to evaluate visual functioning of a compromised visual system effectively.  The American Medical Association provide an approach to evaluating visual loss as it affects an individual's ability to perform activities of daily living.[http://www.ski.org/Colenbrander/Images/AMA_Guides_Vision5_01.pdf AMA Guides]

Screening adults who have no symptoms is of uncertain benefit.

Prevention

The World Health Organization estimates that 80% of visual loss is either preventable or curable with treatment. This includes cataracts, onchocerciasis, trachoma, glaucoma, diabetic retinopathy, uncorrected refractive errors, and some cases of childhood blindness. The Center for Disease Control and Prevention estimates that half of blindness in the United States is preventable.

Treatment

Aside from medical help, various sources provide information, rehabilitation, education, and work and social integration.

Mobility

Many people with serious visual impairments can travel independently, using a wide range of tools and techniques. Orientation and mobility specialists are professionals who are specifically trained to teach people with visual impairments how to travel safely, confidently, and independently in the home and the community. These professionals can also help blind people to practice travelling on specific routes which they may use often, such as the route from one's house to a convenience store. Becoming familiar with an environment or route can make it much easier for a blind person to navigate successfully.

Tools such as the white cane with a red tip – the international symbol of blindness – may also be used to improve mobility. A long cane is used to extend the user's range of touch sensation. It is usually swung in a low sweeping motion, across the intended path of travel, to detect obstacles. However, techniques for cane travel can vary depending on the user and/or the situation. 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. The choice depends on the individual's vision, motivation, and other factors.

A small number of people employ guide dogs to assist in mobility. These dogs are trained to navigate around various obstacles, and to indicate when it becomes necessary to go up or down a step. However, the helpfulness of guide dogs is limited by the inability of dogs to understand complex directions. The human half of the guide dog team does the directing, based upon skills acquired through previous mobility training. In this sense, the handler might be likened to an aircraft's navigator, who must know how to get from one place to another, and the dog to the pilot, who gets them there safely.

GPS devices can also be used as a mobility aid. Such software can assist blind people with orientation and navigation, but it is not a replacement for traditional mobility tools such as white canes and guide dogs.

Some blind people are skilled at echolocating silent objects simply by producing mouth clicks and listening to the returning echoes. It has been shown that blind echolocation experts use what is normally the "visual" part of their brain to process the echoes. 

Government actions are sometimes taken to make public places more accessible to blind people. Public transportation is freely available to the blind in many cities. Tactile paving and audible traffic signals can make it easier and safer for visually impaired pedestrians to cross streets. 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.

Reading and magnification

Most visually impaired people who are not totally blind read print, either of a regular size or enlarged by magnification devices. Many also read large-print, which is easier for them to read without such devices. A variety of magnifying glasses, some handheld, and some on desktops, can make reading easier for them.

Others read Braille (or the infrequently used Moon type), or rely on talking books and readers or reading machines, which convert printed text to speech or Braille. They use computers with special hardware such as scanners and refreshable Braille displays as well as software written specifically for the blind, such as optical character recognition applications and screen readers.

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.

There are also over 100 radio reading services throughout the world that provide people with vision impairments with readings from periodicals over the radio. The International Association of Audio Information Services provides links to all of these organizations.

Computers

Access technology such as screen readers, screen magnifiers and refreshable Braille displays enable the blind to use mainstream computer applications and mobile phones. The availability of assistive technology is increasing, accompanied by concerted efforts to ensure the accessibility of information technology to all potential users, including the blind. Later versions of Microsoft Windows include an Accessibility Wizard & Magnifier for those with partial vision, and Microsoft Narrator, a simple screen reader. 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. Mac OS also comes with a built-in screen reader, called VoiceOver.

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.

Modified visual output that includes large print and/or clear simple graphics can be of benefit to users with some residual vision. 

Other aids and techniques

Blind people may use talking equipment such as thermometers, watches, clocks, scales, calculators, and compasses. They may also enlarge or mark dials on devices such as ovens and thermostats to make them usable. Other techniques used by blind people to assist them in daily activities include:

*Adaptations of coins and banknotes so that the value can be determined by touch. For example:
** In some currencies, such as the euro, the pound sterling and the Indian rupee, the size of a note increases with its value.
** On US coins, pennies and dimes, and nickels and quarters are similar in size. The larger denominations (dimes and quarters) have ridges along the sides (historically used to prevent the "shaving" of precious metals from the coins), which can now be used for identification.
** Some currencies' banknotes have a tactile feature to indicate denomination. For example, the Canadian currency tactile feature is a system of raised dots in one corner, based on Braille cells but not standard Braille. 
** 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 the blind, there are books in braille, audio-books, and text-to-speech computer programs, machines and e-book readers. Low vision people can make use of these tools as well as large-print reading materials and e-book readers that provide large font sizes.

Computers are important tools of integration for the visually impaired person. They allow, using standard or specific programs, screen magnification and conversion of text into sound or touch (Braille line), and are useful for all levels of visual handicap. OCR scanners can, in conjunction with text-to-speech software, read the contents of books and documents aloud via computer. Vendors also build closed-circuit televisions that electronically magnify paper, and even change its contrast and color, for visually impaired users. For more information, consult Assistive technology.

In adults with low vision there is no conclusive evidence supporting one form of reading aid over another. In several studies stand-based closed-circuit television and hand-held closed-circuit television allowed faster reading than optical aids.  While electronic aids may allow faster reading for individuals with low vision, portability, ease of use, and affordability must be considered for people.

Children with low vision sometimes have reading delays, but do benefit from phonics-based beginning reading instruction methods. Engaging phonics instruction is multisensory, highly motivating, and hands-on. Typically students are first taught the most frequent sounds of the alphabet letters, especially the so-called short vowel sounds, then taught to blend sounds together with three-letter consonant-vowel-consonant words such as cat, red, sit, hot, sun. Hands-on (or kinesthetically appealing) VERY enlarged print materials such as those found in "The Big Collection of Phonics Flipbooks" by Lynn Gordon (Scholastic, 2010) are helpful for teaching word families and blending skills to beginning readers with low vision. Beginning reading instructional materials should focus primarily on the lower-case letters, not the capital letters (even though they are larger) because reading text requires familiarity (mostly) with lower-case letters. Phonics-based beginning reading should also be supplemented with phonemic awareness lessons, writing opportunities, and lots of read-alouds (literature read to children daily) to stimulate motivation, vocabulary development, concept development, and comprehension skill development. Many children with low vision can be successfully included in regular education environments. Parents may need to be vigilant to ensure that the school provides the teacher and students with appropriate low vision resources, for example technology in the classroom, classroom aide time, modified educational materials, and consultation assistance with low vision experts.

Communication

Communication with the visually impaired can be more difficult than communicating with someone who doesn't have vision loss. However, many people are uncomfortable with communicating with the blind, and this can cause communication barriers. One of the biggest obstacles in communicating with visually impaired individuals comes from face-to-face interactions.  There are many factors that can cause the sighted to become uncomfortable while communicating face to face. There are many non-verbal factors that hinder communication between the visually impaired and the sighted, more often than verbal factors do. These factors, which Rivka Bialistock mentions in her article, include:

*Lack of facial expressions, mimics, or body gestures/responses
*Non-verbal gestures that could imply the visually impaired individual not appearing interested
*Speaking when not anticipated or not speaking when anticipated
*Fear of offending the visually impaired
*Standing too close and invading the personal comfort level
*Having to exercise or ignore feelings of pity
*Being uncomfortable with touching objects or people
*A look of detachment or disengagement
*Dependency
*Being reminded of the fear of becoming blind

The blind person sends these signals or types of non-verbal communication without being aware that they are doing so. These factors can all affect the way an individual would feel about communicating with the visually impaired. This leaves the visually impaired feeling rejected and lonely.

Adjusting attitude

In the article Towards better communication, from the interest point of view. Or—skills of sight-glish for the blind and visually impaired, the author, Rivka Bialistock  comes up with a method to reduce individuals being uncomfortable with communicating with the visually impaired. This method is called blind-glish or sight-glish, which is a language for the blind, similar to English. For example, babies, who are not born and able to talk right away, communicate through sight-glish, simply seeing everything and communicating non-verbally. This comes naturally to sighted babies, and by teaching this same method to babies with a visual impairment can improve their ability to communicate better, from the very beginning.

To avoid the rejected feeling of the visually impaired, people need to treat the blind the same way they would treat anyone else, rather than treating them like they have a disability, and need special attention. People may feel that it is improper to, for example, tell their blind child to look at them when they are speaking. However, this contributes to the sight-glish method. It is important to disregard any mental fears or uncomfortable feelings people have while communicating (verbally and non-verbally) face-to-face.

Surroundings

Individuals with a visual disability not only have to find ways to communicate effectively with the people around them, but their environment as well. The blind or visually impaired rely largely on their other senses such as hearing, touch, and smell in order to understand their surroundings. 

Sound

Sound is one of the most important senses that the blind or visually impaired use in order to locate objects in their surroundings. A form of echolocation is used, similarly to that of a bat.  Echolocation from a person's perspective is when the person uses sound waves generated from speech or other forms of noise such as cane tapping, which reflect off of objects and bounce back at the person giving them a rough idea of where the object is. This does not mean they can depict details based on sound but rather where objects are in order to interact, or avoid them. Increases in atmospheric pressure and humidity increase a person's ability to use sound to their advantage as wind or any form of background noise impairs it.

Touch

Touch is also an important aspect of how blind or visually impaired people perceive the world. Touch gives immense amount of information in the persons immediate surrounding. Feeling anything with detail gives off information on shape, size, texture, temperature, and many other qualities. Touch also helps with communication; braille is a form of communication in which people use their fingers to feel elevated bumps on a surface and can understand what is meant to be interpreted.  There are some issues and limitations with touch as not all objects are accessible to feel, which makes it difficult to perceive the actual object. Another limiting factor is that the learning process of identifying objects with touch is much slower than identifying objects with sight. This is due to the fact the object needs to be approached and carefully felt until a rough idea can be constructed in the brain.

Smell

Certain smells can be associated with specific areas and help a person with vision problems to remember a familiar area. This way there is a better chance of recognizing an areas layout in order to navigate themselves through. The same can be said for people as well. Some people have their own special odor that a person with a more trained sense of smell can pick up. A person with an impairment of their vision can use this to recognize people within their vicinity without them saying a word.

Communication development

Visual impairment can have profound effects on the development of infant and child communication. The language and social development of a child or infant can be very delayed by the inability to see the world around them.

Social development

Social development includes interactions with the people surrounding the infant in the beginning of its life. To a child with vision, a smile from a parent is the first symbol of recognition and communication, and is almost an instant factor of communication. For a visually impaired infant, recognition of a parent's voice will be noticed at approximately two months old, but a smile will only be evoked through touch between parent and baby. This primary form of communication is greatly delayed for the child and will prevent other forms of communication from developing. Social interactions are more complicated because subtle visual cues are missing and facial expressions from others are lost.

Due to delays in a child's communication development, they may appear to be disinterested in social activity with peers, non-communicative and un-education on how to communicate with other people. This may cause the child to be avoided by peers and consequently over protected by family members.

Language development

With sight, much of what is learned by a child is learned through imitation of others, where as a visually impaired child needs very planned instruction directed at the development of postponed imitation. A visually impaired infant may jabber and imitate words sooner than a sighted child, but may show delay when combining words to say themselves, the child may tend to initiate few questions and their use of adjectives is infrequent. Normally the child's sensory experiences are not readily coded into language and this may cause them to store phrases and sentences in their memory and repeat them out of context. The language of the blind child does not seem to mirror his developing knowledge of the world, but rather his knowledge of the language of others.

A visually impaired child may also be hesitant to explore the world around them due to fear of the unknown and also may be discouraged from exploration by overprotective family members. Without concrete experiences, the child is not able to develop meaningful concepts or the language to describe or think about them. 

Healthcare access

Visual impairment has the ability to create consequences for health and well being. Visual impairment is increasing especially among older people. It is recognized that those individuals with visual impairment are likely to have limited access to information and healthcare facilities, and may not receive the best care possible because not all health care professionals are aware of specific needs related to vision.
*A prerequisite of effective health care could very well be having staff that are aware that people may have problems with vision.
*Communication and different ways of being able to communicate with visually impaired clients must be tailored to individual needs and available at all times.

Epidemiology

The WHO estimates that in 2012 there were 285 million visually impaired people in the world, of which 246 million had low vision and 39 million were blind.

Of those who are blind 90% live in the developing world.  Worldwide for each blind person, an average of 3.4 people have low vision, with country and regional variation ranging from 2.4 to 5.5. 

By age: Visual impairment is unequally distributed across age groups. More than 82% of all people who are blind are 50 years of age and older, although they represent only 19% of the world's population. Due to the expected number of years lived in blindness (blind years), childhood blindness remains a significant problem, with an estimated 1.4 million blind children below age 15.

By gender: Available studies consistently indicate that in every region of the world, and at all ages, females have a significantly higher risk of being visually impaired than males.

By geography: Visual impairment is not distributed uniformly throughout the world. More than 90% of the world's visually impaired live in developing countries.

Since the estimates of the 1990s, new data based on the 2002 global population show a reduction in the number of people who are blind or visually impaired, and those who are blind from the effects of infectious diseases, but an increase in the number of people who are blind from conditions related to longer life spans.

In 1987, it was estimated that 598,000 people in the United States met the legal definition of blindness.  Of this number, 58% were over the age of 65. In 1994–1995, 1.3 million Americans reported legal blindness. 

Society and culture

Legal definition

To determine which people qualify for special assistance because of their visual disabilities, various governments have specific definitions for legal blindness.  In North America and most of Europe, legal blindness is defined as visual acuity (vision) of 20/200 (6/60) or less in the better eye with best correction possible. This means that a legally blind individual would have to stand 20 ft from an object to see it—with corrective lenses—with the same degree of clarity as a normally sighted person could from 200 ft. In many areas, people with average acuity who nonetheless have a visual field of less than 20 degrees (the norm being 180 degrees) are also classified as being legally blind.
Approximately ten percent of those deemed legally blind, by any measure, have no vision. The rest have some vision, from light perception alone to relatively good acuity. Low vision is sometimes used to describe visual acuities from 20/70 to 20/200. 

Literature and art

Antiquity

The Moche people of ancient Peru depicted the blind in their ceramics. 

In Greek myth, Tiresias was a prophet famous for his clairvoyance. According to one myth, he was blinded by the gods as punishment for revealing their secrets, while another holds that he was blinded as punishment after he saw Athena naked while she was bathing. In the Odyssey, the one-eyed Cyclops Polyphemus captures Odysseus, who blinds Polyphemus to escape. In Norse mythology, Loki tricks the blind god Höðr into killing his brother Baldr, the god of happiness.

The New Testament contains numerous instances of Jesus performing miracles to heal the blind. According to the Gospels, Jesus healed the two blind men of Galilee, the blind man of Bethsaida, the blind man of Jericho and the man who was born blind.

The parable of the blind men and an elephant has crossed between many religious traditions and is part of Jain, Buddhist, Sufi and Hindu lore. In various versions of the tale, a group of blind men (or men in the dark) touch an elephant to learn what it is like. Each one feels a different part, but only one part, such as the side or the tusk. They then compare notes and learn that they are in complete disagreement.

"Three Blind Mice" is a medieval English nursery rhyme about three blind mice whose tails are cut off after chasing the farmer's wife. The work is explicitly incongruous, ending with the comment Did you ever see such a sight in your life, As three blind mice?

Modern times

Poet John Milton, who went blind in mid-life, composed On His Blindness, a sonnet about coping with blindness. The work posits that [those] who best Bear [God]'s mild yoke, they serve him best.

The Dutch painter and engraver Rembrandt often depicted scenes from the apocryphal Book of Tobit, which tells the story of a blind patriarch who is healed by his son, Tobias, with the help of the archangel Raphael. 

Slaver-turned-abolitionist John Newton composed the hymn Amazing Grace about a wretch who "once was lost, but now am found, Was blind, but now I see." Blindness, in this sense, is used both metaphorically (to refer to someone who was ignorant but later became knowledgeable) and literally, as a reference to those healed in the Bible. In the later years of his life, Newton himself would go blind.

H. G. Wells' story "The Country of the Blind" explores what would happen if a sighted man found himself trapped in a country of blind people to emphasise society's attitude to blind people by turning the situation on its head.

Bob Dylan's anti-war song "Blowin' in the Wind" twice alludes to metaphorical blindness: How many times can a man turn his head // and pretend that he just doesn't see... How many times must a man look up // Before he can see the sky?

Contemporary fiction contains numerous well-known blind characters. Some of these characters can "see" by means of fictitious devices, such as the Marvel Comics superhero Daredevil, who can "see" via his super-human hearing acuity, or Star Treks Geordi La Forge, who can see with the aid of a VISOR, a fictitious device that transmits optical signals to his brain.

Sports

Blind and partially sighted people participate in sports, such as swimming, snow skiing and athletics. Some sports have been invented or adapted for the blind, such as goalball, association football, cricket, golf, and tennis.  The worldwide authority on sports for the blind is the International Blind Sports Federation.  People with vision impairments have participated in the Paralympic Games since the 1976 Toronto summer Paralympics. 

Metaphorical uses

The word "blind" (adjective and verb) is often used to signify a lack of knowledge of something. For example, a blind date is a date in which the people involved have not previously met; a blind experiment is one in which information is kept from either the experimenter or the participant to mitigate the placebo effect or observer bias. The expression "blind leading the blind" refers to incapable people leading other incapable people. Being blind to something means not understanding or being aware of it. A "blind spot" is an area where someone cannot see: for example, where a car driver cannot see because parts of his car's bodywork are in the way; metaphorically, a topic on which an individual is unaware of their own biases, and therefore of the resulting distortions of their own judgements (see Bias blind spot).

Research

A 2008 study tested the effect of using gene therapy to help restore the sight of patients with a rare form of inherited blindness, known as Leber's congenital amaurosis or LCA.  Leber's Congenital Amaurosis damages the light receptors in the retina and usually begins affecting sight in early childhood, with worsening vision until complete blindness around the age of 30.

The study used a common cold virus to deliver a normal version of the gene called RPE65 directly into the eyes of affected patients. Remarkably, all 3 patients, aged 19, 22 and 25, responded well to the treatment and reported improved vision following the procedure. Due to the age of the patients and the degenerative nature of LCA, the improvement of vision in gene therapy patients is encouraging for researchers. It is hoped that gene therapy may be even more effective in younger LCA patients who have experienced limited vision loss, as well as in other blind or partially blind individuals.

Two experimental treatments for retinal problems include a cybernetic replacement and transplant of fetal retinal cells. 

Other animals

Statements that certain species of mammals are "born blind" refers to them being born with their eyes closed and their eyelids fused together; the eyes open later. One example is the rabbit. In humans, the eyelids are fused for a while before birth, but open again before the normal birth time; however, very premature babies are sometimes born with their eyes fused shut, and opening later. Other animals, such as the blind mole rat, are truly blind and rely on other senses.

The theme of blind animals has been a powerful one in literature. Peter Shaffer's Tony-Award winning play, Equus, tells the story of a boy who blinds six horses. Theodore Taylor's classic young adult novel, The Trouble With Tuck, is about a teenage girl, Helen, who trains her blind dog to follow and trust a seeing-eye dog. Braille is a tactile writing system used by people who are blind or visually impaired. It is traditionally written with embossed paper.  Braille-users can read computer screens and other electronic supports thanks to refreshable braille displays. They can write braille with the original slate and stylus or type it on a braille writer, such as a portable braille note-taker, or on a computer that prints with a braille embosser.

Braille is named after its creator, Frenchman Louis Braille, who lost his eyesight due to a childhood accident. In 1824, at the age of 15, Braille developed his code for the French alphabet as an improvement on night writing. He published his system, which subsequently included musical notation, in 1829.   The second revision, published in 1837, was the first binary form of writing developed in the modern era.

Braille characters are small rectangular blocks called cells that contain tiny palpable bumps called raised dots. The number and arrangement of these dots distinguish one character from another. Since the various braille alphabets originated as transcription codes of printed writing systems, the mappings (sets of character designations) vary from language to language. Furthermore, in English Braille there are three levels of encoding: Grade 1 - a letter-by-letter transcription used for basic literacy; Grade 2 - an addition of abbreviations and contractions; and Grade 3 - various non-standardized personal shorthands.

Braille cells are not the only thing to appear in braille text. There may be embossed illustrations and graphs, with the lines either solid or made of series of dots, arrows, bullets that are larger than braille dots, etc. A full Braille cell includes six raised dots arranged in two lateral rows each having three dots.  The dot positions are identified by numbers from one through six. 64 solutions are possible from using one or more dots. A single cell can be used to represent an alphabet letter, number, punctuation mark, or even an entire word.

In the face of screen-reader software, braille usage has declined. However, braille education remains important for developing reading skills among blind and visually impaired children, and braille literacy correlates with higher employment rates.

History

Braille was based on a tactile military code called night writing, developed by Charles Barbier in response to Napoleon's demand for a means for soldiers to communicate silently at night and without a light source.  In Barbier's system, sets of 12 embossed dots encoded 36 different sounds. It proved to be too difficult for soldiers to recognize by touch, and was rejected by the military. In 1821 Barbier visited the Royal Institute for the Blind in Paris, where he met Louis Braille. Braille identified two major defects of the code: first, by representing only sounds, the code was unable to render the orthography of the words; second, the human finger could not encompass the whole 12-dot symbol without moving, and so could not move rapidly from one symbol to another. Braille's solution was to use 6-dot cells and to assign a specific pattern to each letter of the alphabet.
At first, braille was a one-to-one transliteration of French orthography, but soon various abbreviations, contractions, and even logograms were developed, creating a system much more like shorthand. The expanded English system, called Grade-2 Braille, was complete by 1905. To blinds, Braille is an independent writing system, rather than a code of printed orthography.

Derivation

Braille is derived from the Latin alphabet, albeit indirectly. In Braille's original system, the dot patterns were assigned to letters according to their position within the alphabetic order of the French alphabet, with accented letters and w sorted at the end. 

The first ten letters of the alphabet, a–j, use the upper four dot positions:  (black dots in the table below). These stand for the ten digits 1–9 and 0 in a system parallel to Hebrew gematria and Greek isopsephy. (Though the dots are assigned in no obvious order, the cells with the fewest dots are assigned to the first three letters (and lowest digits), abc = 123 (), and to the three vowels in this part of the alphabet, aei (), whereas the even digits, 4, 6, 8, 0 (), are corners/right angles.)

The next ten letters, k–t, are identical to a–j, respectively, apart from the addition of a dot at position 3 (red dots in the table): :

The next ten letters (the next "decade") are the same again, but with dots also at positions both 3 and 6 (green dots). Here w was left out as not being a part of the basic French alphabet; the French braille order is u v x y z ç é à è ù (). 

The next ten, ending in w, are the same again, except that for this series position 6 (purple dot) is used without position 3. These are â ê î ô û ë ï ü ö w (). 

The a–j series lowered by one dot space () are used for punctuation.  Letters a  and c , which only use dots in the top row, were lowered two places for the apostrophe and hyphen: . (These are the decade diacritics, at left in the table below, of the second and third decade.)

In addition, there are ten patterns that are based on the first two letters () shifted to the right; these were assigned to non-French letters (ì ä ò ), or serve non-letter functions:  (superscript; in English the accent mark),  (currency prefix),  (capital, in English the decimal point),  (number sign),  (emphasis mark),  (symbol prefix).

Originally there had been nine decades. The fifth through ninth used dashes as well as dots, but proved to be impractical and were soon abandoned. These could be replaced with what we now know as the number sign (), though that only caught on for the digits (old 5th decade → modern 1st decade). The dash occupying the top row of the original sixth decade was simply dropped, producing the modern fifth decade. (See 1829 braille.)

Assignment

Historically, there have been three principles in assigning the values of a linear script (print) to braille:  Using Louis Braille's original French letter values; reassigning the braille letters according to the sort order of the print alphabet being transcribed; and reassigning the letters to improve the efficiency of writing in braille.

Under international consensus, most braille alphabets follow the French sorting order for the 26 letters of the basic Latin alphabet, and there have been attempts at unifying the letters beyond these 26 (see international braille), though differences remain, for example in German Braille and the contractions of English Braille. This unification avoids the chaos of each nation reordering the braille code to match the sorting order of its print alphabet, as happened in Algerian Braille, where braille codes were numerically reassigned to match the order of the Arabic alphabet and bear little relation to the values used in other countries (compare modern Arabic Braille, which uses the French sorting order), and as happened in an early American version of English Braille, where the letters w, x, y, z were reassigned to match English alphabetical order.  A convention sometimes seen for letters beyond the basic 26 is to exploit the physical symmetry of braille patterns iconically, for example, by assigning a reversed n to ñ or an inverted s to sh. (See Hungarian Braille and Bharati Braille, which do this to some extent.)

A third principle was to assign braille codes according to frequency, with the simplest patterns (quickest ones to write) assigned to the most frequent letters of the alphabet. Such frequency-based alphabets were used in Germany and the United States in the 19th century (see American Braille), but none are attested in modern use. Finally, there are braille scripts which don't order the codes numerically at all, such as Japanese Braille and Korean Braille, which are based on more abstract principles of syllable composition.

Academic texts are sometimes written in a script of eight dots per cell rather than six, enabling them to encode a greater number of symbols. (See Gardner–Salinas braille codes.) Luxembourgish Braille has adopted eight-dot cells for general use; for example, it adds a dot below each letter to derive its capital variant.

Form

Braille was the first writing system with binary encoding.Peter Daniels, 1996, "Analog and Digital Writing", in The World's Writing Systems, p 886 The system as devised by Braille consists of two parts:Daniels & Bright, 1996, The World's Writing Systems, p 817–818
#Character encoding that mapped characters of the French alphabet to tuples of six bits (the dots),
#The physical representation of those six-bit characters with raised dots in a braille cell.

Within an individual cell, the dot positions are arranged as two columns of three positions. A raised dot can appear in any of the six positions, producing sixty-four (26) possible patterns, including one in which there are no raised dots. For reference purposes, a pattern is commonly described by listing the positions where dots are raised, the positions being universally numbered, from top to bottom, as 1 to 3 on the left and 4 to 6 on the right. For example, dot pattern 1-3-4 describe a cell with three dots raised, at the top and bottom in the left column and at the top of the right column:  that is, the letter  m. The lines of horizontal braille text are separated by a space, much like visible printed text, so that the dots of one line can be differentiated from the braille text above and below. Different assignments of braille codes (or code pages) are used to map the character sets of different printed scripts to the six-bit cells. Braille assignments have also been created for mathematical and musical notation. However, because the six-dot braille cell allows only 64 (26) patterns, including the space, the characters of a braille script commonly have multiple values, depending on their context. That is, character mapping between print and braille is not one-to-one.  For example, the character  corresponds in print to both the letter d and the digit 4.

In addition to simple encoding, many braille alphabets use contractions to reduce the size of braille texts and to increase reading speed. (See Contracted braille)

Writing braille

Braille may be produced by hand using a slate and stylus in which each dot is created from the back of the page, writing in mirror image, or it may be produced on a braille typewriter or Perkins Brailler, or an electronic Brailler or eBrailler. Because braille letters cannot be effectively erased and written over if an error is made, an error is overwritten with all six dots (). Interpoint refers to braille printing that is offset, so that the paper can be embossed on both sides, with the dots on one side appearing between the divots that form the dots on the other (see the photo in the box at the top of this article for an example).
Using a computer or other electronic device, braille may be produced with a braille embosser (printer) or a refreshable braille display (screen).

Braille has been extended to an 8-dot code, particularly for use with braille embossers and refreshable braille displays. In 8-dot braille the additional dots are added at the bottom of the cell, giving a matrix 4 dots high by 2 dots wide. The additional dots are given the numbers 7 (for the lower-left dot) and 8 (for the lower-right dot). Eight-dot braille has the advantages that the case of an individual letter is directly coded in the cell containing the letter and that all the printable ASCII characters can be represented in a single cell. All 256 (28) possible combinations of 8 dots are encoded by the Unicode standard. Braille with six dots is frequently stored as Braille ASCII.

Letters

The first 25 braille letters, up through the first half of the 3rd decade, transcribe a–z (skipping w). In English Braille, the rest of that decade is rounded out with the ligatures and, for, of, the, and with. Omitting dot 3 from these forms the 4th decade, the ligatures ch, gh, sh, th, wh, ed, er, ou, ow and the letter w.

(See English Braille.)

Formatting

Various formatting marks affect the values of the letters that follow them. They have no direct equivalent in print. The most important in English Braille are:

That is,  is read as capital 'A', and  as the digit '1'.

Punctuation

Basic punctuation marks in English Braille include:

 is both the question mark and the opening quotation mark. Its reading depends on whether it occurs before a word or after.

 is used for both opening and closing parentheses. Its placement relative to spaces and other characters determines its interpretation.

Punctuation varies from language to language. For example, French Braille uses  for its question mark and swaps the quotation marks and parentheses (to  and ); it uses the period () for the decimal point, as in print, and the decimal point () to mark capitalization.

Contractions

Braille contractions are words and affixes that are shortened so that they take up fewer cells. In English Braille, for example, the word afternoon is written with just three letters,  , much like stenoscript. There are also several abbreviation marks that create what are effectively logograms. The most common of these is dot 5, which combines with the first letter of words. With the letter  m, the resulting word is  mother. There are also ligatures ("contracted" letters), which are single letters in braille but correspond to more than one letter in print. The letter  and, for example, is used to write words with the sequence a-n-d in them, such as  hand.

Page dimensions

Most braille embossers support between 34 and 40 cells per line, and 25 lines per page.

A manually operated Perkins braille typewriter supports a maximum of 42 cells per line (its margins are adjustable), and typical paper allows 25 lines per page.

A large interlining Stainsby has 36 cells per line and 18 lines per page.

An A4-sized Marburg braille frame, which allows interpoint braille (dots on both sides of the page, offset so they do not interfere with each other) has 30 cells per line and 27 lines per page.

Literacy

A sighted child who is reading at a basic level should be able to understand common words and answer simple questions about the information presented.  The child should also have enough fluency to get through the material in a timely manner. Over the course of a child's education, these foundations are built upon in order to teach higher levels of math, science, and comprehension skills. Children who are blind not only have the educational disadvantage of not being able to see, but they also miss out on the very fundamental parts of early and advanced education if not provided with the necessary tools. Children who are blind or visually impaired can begin learning pre-braille skills from a very young age in order to become fluent braille readers as they get older.

U.S. braille literacy statistics

In 1960, 50% of legally blind, school-age children were able to read braille in the U.S.  According to the 2011 Annual Report from the American Printing House for the Blind, there are approximately 58,939 legally blind children in the U.S aged 0–21. Of these, about 9% prefer braille as their primary reading medium; 27% are visual readers, 8% are auditory readers, 21% are pre-readers, and 34% are non-readers.

There are numerous causes for the decline in braille usage, including school budget constraints, technology advancement, and different philosophical views over how blind children should be educated.

A key turning point for braille literacy was the passage of the Rehabilitation Act of 1973, an act of Congress that moved thousands of children from specialized schools for the blind into mainstream public schools. Because only a small percentage of public schools could afford to train and hire braille-qualified teachers, braille literacy has declined since the law took effect. Braille literacy rates have improved slightly since the bill was passed, in part because of pressure from consumers and advocacy groups that has led 27 states to pass legislation mandating that children who are legally blind be given the opportunity to learn braille.

In 1998–99, there were approximately 55,200 legally blind children in the United States, but only 5,500 of them used braille as their primary reading medium.  Early braille education is crucial to literacy for a blind or low vision child. A study conducted in the state of Washington found that people who learned braille at an early age did just as well, if not better, than their sighted peers in several areas, including vocabulary and comprehension.  In the preliminary adult study, while evaluating the correlation between adult literacy skills and employment, it was found that 44% of the participants who had learned to read in braille were unemployed, compared to the 77% unemployment rate of those who had learned to read using print.  Currently, among the estimated 85,000 blind adults in the United States, 90% of those who are braille-literate are employed. Among adults who do not know braille, only 33% are employed. Statistically, history has proven that braille reading proficiency provides an essential skill set that allows blind or low vision children not only to compete with their sighted peers in a school environment, but also later in life as they enter the workforce.

United Kingdom

Though braille is thought to be the main way blind people read and write, in Britain (for example) out of the reported 2 million blind and low vision population, it is estimated that only around 15–20 thousand people use braille.  Younger people are turning to electronic text on computers with screen reader software instead, a more portable communication method that they can also use with their friends. A debate has started on how to make braille more attractive and for more teachers to be available to teach it.

Braille transcription

Although it is possible to transcribe print by simply substituting the equivalent braille character for its printed equivalent, in English such a character-by-character transcription (known as uncontracted braille) is only used by beginners.

Braille characters are much larger than their printed equivalents, and the standard 11" by 11.5" (28 cm × 30 cm) page has room for only 25 lines of 43 characters. To reduce space and increase reading speed, most braille alphabets and orthographies use ligatures, abbreviations, and contractions. Virtually all English Braille books are transcribed in this contracted braille, which adds an additional layer of complexity to English orthography: The Library of Congress's Instruction Manual for Braille Transcribing  runs to over 300 pages and braille transcribers must pass certification tests.

Fully contracted braille is known as Grade 2 Braille. There is an intermediate form between Computer Braille—one-for-one identity with print—and Grade 2, which is called Grade 1 Braille.  In Grade 1 the capital-sign and Number sign are used, and most punctuation marks are shown using their Grade 2 values.

The system of contractions in English Braille begins with a set of 23 words which are contracted to single characters. Thus the word but is contracted to the single letter b, can to c, do to d, and so on. Even this simple rule creates issues requiring special cases; for example, d is, specifically, an abbreviation of the verb do; the noun do representing the note of the musical scale is a different word, and must be spelled out.

Portions of words may be contracted, and many rules govern this process. For example, the character with dots 2-3-5 (the letter "f" lowered in the braille cell) stands for "ff" when used in the middle of a word. At the beginning of a word, this same character stands for the word "to"; the character is written in braille with no space following it. (This contraction was removed in the Unified English Braille Code.) At the end of a word, the same character represents an exclamation point.

Some contractions are more similar than their print equivalents. For example, the contraction , meaning 'letter', differs from , meaning 'little', only in adding one dot to the second :  little,  letter. This causes greater confusion between the braille spellings of these words and can hinder the learning process of contracted braille. 

The contraction rules take into account the linguistic structure of the word; thus, contractions are generally not to be used when their use would alter the usual braille form of a base word to which a prefix or suffix has been added. Some portions of the transcription rules are not fully codified and rely on the judgment of the transcriber. Thus, when the contraction rules permit the same word in more than one way, preference is given to "the contraction that more nearly approximates correct pronunciation."

Grade 3 Braille  is a variety of non-standardized systems that include many additional shorthand-like contraction. They are not used for publication, but by individuals for their personal convenience.

Braille translation software

When people produce braille, this is called braille transcription. When computer software produces braille, this is called braille
translation. Braille translation software exists to handle most of the common languages of the world, and many technical areas,
such as mathematics (mathematical notation), for example WIMATS, music (musical notation), and tactile graphics.

Braille-reading techniques

Since braille is one of the few writing systems where tactile perception is used, as opposed to visual perception, a braille reader must develop new skills.  One skill important for braille readers is the ability to create smooth and even pressures when running one's fingers along the words.  There are many different styles and techniques used for the understanding and development of braille, even though a study by B. F. Holland  suggests that there is no specific technique that is superior to any other.

Another study by Lowenfield & Abel  shows that braille could be read "the fastest and best... by students who read using the index fingers of both hands."  Another important reading skill emphasized in this study is to finish reading the end of a line with the right hand and to find the beginning of the next line with the left hand simultaneously.  One final conclusion drawn by both Lowenfield and Abel is that children have difficulty using both hands independently where the right hand is the dominant hand.  But this hand preference does not correlate to other activities.

International uniformity

When braille was first adapted to languages other than French, many schemes were adopted, including mapping the native alphabet to the alphabetical order of French – e.g. in English W, which was not in the French alphabet at the time, is mapped to braille X, X to Y, Y to Z, and Z to the first French accented letter – or completely rearranging the alphabet such that common letters are represented by the simplest braille patterns. Consequently, mutual intelligibility was greatly hindered by this state of affairs. In 1878, the International Congress on Work for the Blind, held in Paris, proposed an international braille standard, where braille codes for different languages and scripts would be based, not on the order of a particular alphabet, but on phonetic correspondence and transliteration to Latin.

This unified braille has been applied to the languages of India and Africa, Arabic, Vietnamese, Hebrew, Russian, and Armenian, as well as nearly all Latin-script languages. Greek, for example, gamma is written as Latin g, despite the fact that it has the alphabetic position of c; Hebrew bet, the second letter of the alphabet and cognate with the Latin letter b, is sometimes pronounced /b/ and sometimes /v/, and is written b or v accordingly; Russian ts is written as c, which is the usual letter for /ts/ in those Slavic languages that use the Latin alphabet; and Arabic f is written as f, despite being historically p, and occurring in that part of the Arabic alphabet (between historic o and q).

Other braille conventions

Other systems for assigning values to braille patterns are also followed, beside the simple mapping of the alphabetical order onto the original French order. Some braille alphabets start with unified braille, and then diverge significantly based on the phonology of the target languages, while others diverge even further.

In the various Chinese systems, traditional braille values are used for initial consonants and the simple vowels. In both Mandarin and Cantonese Braille, however, characters have different readings depending on whether they are placed in syllable-initial (onset) or syllable-final (rime) position. For instance, the cell for Latin k, , represents Cantonese k (g in Yale and other modern romanizations) when initial, but aak when final, while Latin j, , represents Cantonese initial j but final oei.

Novel systems of braille mapping include Korean, which adopts separate syllable-initial and syllable-final forms for its consonants, explicitly grouping braille cells into syllabic groups in the same way as hangul. Japanese, meanwhile, combines independent vowel dot patterns and modifier consonant dot patterns into a single braille cell – an abugida representation of each Japanese mora.

Uses

The current series of Canadian banknotes has a tactile feature consisting of raised dots that indicate the denomination, allowing bills to be easily identified by blind or low vision people. It does not use standard braille; rather, the feature uses a system developed in consultation with blind and low vision Canadians after research indicated that braille was not sufficiently robust and that not all potential users read braille. Mexican bank notes, Indian rupee notes, Israeli New Shekel notes,  Russian Ruble and Swiss Franc notes also have special raised symbols to make them identifiable by persons who are blind or low vision. 

In India there are instances where the parliament acts have been published in braille, such as The Right to Information Act. 

In the United States, the Americans with Disabilities Act of 1990  requires various building signage to be in braille.

In the United Kingdom, it is required that medicines have the name of the medicine in Braille on the labelling. 

Unicode

Braille was added to the Unicode Standard in September, 1999 with the release of version 3.0.

Most braille embossers and refreshable braille displays do not support Unicode, using instead 6-dot braille ASCII.  Because of this, they are unable to display this article.  Some embossers have proprietary control codes for 8-dot braille or for full graphics mode, where dots may be placed anywhere on the page without leaving any space between braille cells, so that continuous lines can be drawn in diagrams, but these are rarely used and are not standard.

The Unicode standard encodes 8-dot braille glyphs according to their binary appearance, rather than following their assigned numeric order. Dot 1 corresponds to the least significant bit of the low byte of the Unicode scalar value, and dot 8 to the high bit of that byte.

The Unicode block for braille is U+2800 ... U+28FF:
Braile Braille Keyboard Braille cell Eight-point braille Eight-dot braille Braille book Braille Braille keyboard Braille script ISO 15924:Brai Braille alphabet Braille System Braille code Braille writer Braille contraction Braille (script) Brai (script)
braille script braille alphabet eight dot braille iso 15924 brai braille cell braille book braille contraction brai script eight point braille braille system braille code braille braille keyboard braille writer braile
braille
WikipediaEntity
Braille
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