Visual impairment

Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment – visual impairment may cause the individual difficulties with normal daily tasks including reading and walking.^[6] The terms low vision and blindness are often used for levels of impairment which are difficult or impossible to correct and significantly impact daily life. In addition to the various permanent conditions, fleeting temporary vision impairment, amaurosis fugax, may occur, and may indicate serious medical problems.^[7][8][9]

The most common causes of visual impairment globally are uncorrected

The World Health Organization (WHO) estimates that 80% of visual impairment is either preventable or curable with treatment.^[1] This includes cataracts, the infections river blindness and trachoma, glaucoma, diabetic retinopathy, uncorrected refractive errors, and some cases of childhood blindness.^[14] Many people with significant visual impairment benefit from vision rehabilitation, changes in their environment, and assistive devices.^[2]

As of 2015^[update], there were 940 million people with some degree of vision loss.

In 2010, the WHO definition for visual impairment was changed and now follows the ICD-11. The previous definition which used "best corrected visual acuity" was changed to "presenting visual acuity". This change was made as newer studies showed that best-corrected vision overlooks a larger proportion of the population who has visual impairment due to uncorrected refractive errors, and/or lack of access to medical or surgical treatment.^[16]

Distance vision impairment:

• Category 0: No or mild visual impairment – presenting visual acuity better than 6/18
• Category 1: Moderate visual impairment – presenting visual acuity worse than 6/18 and better than 6/60
• Category 2: Severe visual impairment – presenting visual acuity worse than 6/60 and better than 3/60
• Category 3: Blindness – presenting visual acuity worse than 3/60 and better than 1/60
• Category 4: Blindness – presenting visual acuity worse than 1/60 with light perception
• Category 5: Blindness – irreversible blindness with no light perception

Near vision impairment:

• Near visual acuity worse than N6 or M 0.8 at 40 cm.

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 (10 ft) what the normally sighted person sees at 60 metres (200 ft).

Sight impaired

• Able to see at 3 metres (10 ft), but not at 6 metres (20 ft), what the normally sighted person sees at 60 metres (200 ft)
• 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.^[17]

In the UK, the Certificate of Vision Impairment (CVI) is used to certify patients as severely sight impaired or sight impaired.^[18] 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'". Certification is based on whether a person can do any work for which eyesight is essential, not just one particular job (such as their job before becoming blind).^[19]

In practice, the definition depends on individuals'

1. Those below 3/60 (equivalent to 20/400 in US notation) Snellen (most people below 3/60 are severely sight impaired).
2. Those better than 3/60 but below 6/60 Snellen (people who have a very contracted field of vision only).
3. 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.^[19]

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.

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.^[20] 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.
• 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.^[21]

The United States Congress included this definition as part of the Aid to the Blind program in the Social Security Act passed in 1935.^[21][22] 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^[23] 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.^[24]

Temporary vision impairment

Vision impairment for a few seconds, or minutes, may occur due to any of a variety of causes, some serious and requiring medical attention.

Health effects

General functioning

Visual impairments may take many forms and be of varying degrees. Visual acuity alone is not always a good predictor of an individual's function. 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 they have low visual demands. It is also important to note that best-corrected visual acuity differs from presenting visual acuity; a person with a "normal" best corrected acuity can have "poor" presenting acuity (e.g. individual who has uncorrected refractive error). Thus, measuring an individual's general functioning depends on one's situational and contextual factors, as well as access to treatment.^[25]

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;^[26][27] total loss of vision in both eyes is considered to be 100% visual impairment and 85% impairment of the whole person.^[26]

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

Mobility

Older adults with visual impairment are at an increased risk of physical inactivity,^[28][29] slower gait speeds,^[30][31][32] and fear of falls.^[33]

Physical activity is a useful predictor of overall well-being, and routine physical activity reduces the risk of developing chronic diseases and disability.^[34][35] Older adults with visual impairment (including glaucoma, age-related macular degeneration, and diabetic retinopathy) have decreased physical activity as measured with self-reports and accelerometers.^[36][37] The US National Health and Nutrition Examination Survey (NHANES) showed that people with corrected visual acuity of less than 20/40 spent significantly less time in moderate to vigorous physical activity.^[38] Age-related macular degeneration is also associated with a 50% decrease in physical activity–however physical activity is protective against age-related macular degeneration progression.^[39][40]

In terms of mobility, those with visual impairment have a slower gait speed than those without visual impairment; however, the rate of decline remains proportional with increasing age in both groups. Additionally, the visually impaired also have greater difficulty walking a quarter mile (400 m) and walking up stairs, as compared to those with normal vision.^[41]

Cognitive

Older adults with vision loss are at an increased risk of memory loss, cognitive impairment, and cognitive decline.^[42]

Social and psychological

Studies demonstrate an association between older adults with visual impairment and a poor mental health;^{[43][44][45][46]} discrimination was identified as one of the causes of this association.^[47] Older adults with visual impairment have a 1.5-fold risk of reporting perceived discrimination and of these individuals, there was a 2-fold risk of loneliness and 4-fold risk of reporting a lower quality of life.^[47] Among adults with visual impairment, the prevalence of moderate loneliness is 28.7% (18.2% in general population) and prevalence of severe loneliness is 19.7% (2.7% in general population).^[43] The risk of depression and anxiety are also increased in the visually impaired; 32.2% report depressive symptoms (12.01% in general population), and 15.61% report anxiety symptoms (10.69% in general population).^[45]

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. Many studies have demonstrated how rapid acceptance of the serious visual impairment has led to a better, more productive compliance with rehabilitation programs. Moreover, psychological distress has been reported to be at its highest when sight loss is not complete, but the prognosis is unfavorable. Therefore, early intervention is imperative for enabling successful psychological adjustment.^[48]

Associated conditions

Blindness can occur in combination with such conditions as

It has been estimated that over half of completely 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 (synchronized) to the light–dark cycle.^[51][52]

Cause

The most common causes of visual impairment globally in 2010 were:

1. Refractive error (42%)
2. Cataract (33%)
3. Glaucoma (2%)
4. Age-related macular degeneration
   (1%)
5. Corneal opacification
   (1%)
6. Diabetic retinopathy (1%)
7. Childhood blindness
8. Trachoma (1%)
9. Undetermined (18%)^[10]

The most common causes of blindness worldwide in 2010 were:

1. Cataracts (51%)
2. Glaucoma (8%)
3. Age-related macular degeneration (5%)
4. Corneal opacification (4%)
5. Childhood blindness (4%)
6. Refractive errors (3%)
7. Trachoma (3%)
8. Diabetic retinopathy (1%)
9. Undetermined (21%)^[10]

About 90% of people who are visually impaired live in the

Among working-age adults who are newly blind in England and Wales the most common causes in 2010 were:[54]

1. Hereditary retinal disorders (20.2%)
2. Diabetic retinopathy (14.4%)
3. Optic atrophy (14.1%)
4. Glaucoma (5.9%)
5. Congenital abnormalities (5.1%)
6. Disorders of the visual cortex (4.1%)
7. Cerebrovascular disease (3.2%)
8. Degeneration of the macula and posterior pole (3.0%)
9. Myopia (2.8%)
10. Corneal disorders (2.6%)
11. Malignant neoplasms of the brain and nervous system (1.5%)
12. Retinal detachment (1.4%)

Cataracts

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.^[63]

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

People with albinism often have vision loss to the extent that many are legally blind, though few of them actually cannot see. Leber congenital amaurosis can cause total blindness or severe sight loss from birth or early childhood. Retinitis pigmentosa is characterized by decreased peripheral vision and trouble seeing at night.

Advances in

• Amblyopia: is a category of vision loss or visual impairment that is caused by factors unrelated to refractive errors or coexisting ocular diseases.^[58] Amblyopia is the condition when a child's visual systems fail to mature normally because the child either has been born premature, measles, congenital rubella syndrome, vitamin A deficiency, or meningitis.^[66] If left untreated during childhood, amblyopia is currently incurable in adulthood because surgical treatment effectiveness changes as a child matures.^[66] Consequently, amblyopia is the world's leading cause of child monocular vision loss, which is the damage or loss of vision in one eye.^[58] In the best case scenario, which is very rare, properly treated amblyopia patients can regain 20/40 acuity.^[58]
• 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,^[67] which a measurement of blood glucose or sugar level.^[68] 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).^[67] 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 disease accounted for 17% of cases of blindness in 2002.^[67]
• Retinitis pigmentosa
• Avastin
  therapy.
• Stargardt's disease
• Uveitis: is a group of 30 intraocular inflammatory diseases^[69] caused by infections, systemic diseases, organ-specific autoimmune processes, cancer or trauma.^[70] That is, uveitis refers to a complex category of ocular diseases that can cause blindness if either left untreated or improperly diagnosed.^[70] The current challenge of accurately diagnosing uveitis is that often the cause of a specific ocular inflammation is either unknown or multi-layered.^[69] Consequently, about 3–10% of those with uveitis in developed countries, and about 25% of those with uveitis in the developing countries, become blind from incorrect diagnosis and from ineffectual prescription of drugs, antibiotics or steroids.^[70] 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.^[70] 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.^[70]
• 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.

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.^[71] The American Medical Association provides an approach to evaluating visual loss as it affects an individual's ability to perform activities of daily living.^[26]

Screening adults who have no symptoms is of uncertain benefit.^[13]

Prevention

The World Health Organization estimates that 80% of visual loss is either preventable or curable with treatment.^[1] This includes cataracts, onchocerciasis, trachoma, glaucoma, diabetic retinopathy, uncorrected refractive errors, and some cases of childhood blindness.^[14] The Center for Disease Control and Prevention estimates that half of blindness in the United States is preventable.^[2]

Management

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

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.^[72][73]

Government actions are sometimes taken to make public places more accessible to blind people. Public transportation is freely available to blind people in many cities.

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

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 and mobile technology

Access technology such as

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.^[74]

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.^[75]
  • 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

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 impairment. 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.^[76] In several studies stand-mounted devices allowed faster reading than hand-held or portable optical aids.^[76] While electronic aids may allow faster reading for individuals with low vision, portability, ease of use, and affordability must be considered for people.^[76]

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 many 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.

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.^[1]

Of those who are blind 90% live in the developing world.^[77] 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.^[78]

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.^{[79][80][81][82][83][84]}

By geography: Visual impairment is not distributed uniformly throughout the world. More than 90% of the world's visually impaired live in developing countries.^[78]

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.^[78]

In 1987, it was estimated that 598,000 people in the United States met the legal definition of blindness.^[85] Of this number, 58% were over the age of 65.^[85] In 1994–1995, 1.3 million Americans reported legal blindness.^[86]

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.^[87] 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 feet (6.1 m) from an object to see it – with corrective lenses – with the same degree of clarity as a normally sighted person could from 200 feet (61 m). 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 fifteen percent of those deemed legally blind, by any measure, have no light or form perception. The rest have some vision, from light perception alone to relatively good acuity.

Antiquity

The

"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

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.^[90]

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 culture

People who are not blind often imagine that people who are blind share a cultural identity in the way that other minority groups with shared experiences have a distinct culture.^[91] Various blind commentators have responded to this perception by explaining that more commonly, blind people integrate with the broader community and culture, and often do not identify blindness as a defining part of their culture.^[92][93][94]

People who are blind share the common cultural experience of the many misconceptions sighted people have about living with blindness.^[95]

Sports

Blind and partially sighted people participate in sports, such as

A 2008 study tested the effect of using

Two experimental treatments for retinal problems include a cybernetic replacement and transplant of fetal retinal cells.[102]

There is no high-quality evidence on the effect of assistive technologies on educational outcomes and quality of life in children with low vision as of 2015^[update],^[103] nor is there evidence on magnifying reading aids in children.^[104] Low-vision rehabilitation does not appear to have an important impact on health-related quality of life, though some low-vision rehabilitation interventions, particularly psychological therapies and methods of enhancing vision, may improve vision-related quality of life in people with sight loss.^[105]

Other animals

Statements that certain species of

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.

See also

References

External links

Wikimedia Commons has media related to Visual disturbances and blindness.

• Blindness at
  Curlie
• Chisholm, Hugh, ed. (1911). "Blindness" . Encyclopædia Britannica (11th ed.). Cambridge University Press.

Listen to this article (1 hour and 11 minutes)

Audio help · More spoken articles

)