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
Visual impairment may cause people difficulties with normal
daily activities such as driving, reading, socializing, and
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
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, premature
birth, 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
World Health Organization
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
environment, and assistive devices.
As of 2015 there were 940 million people with some degree of vision
loss. 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.
1.1 United Kingdom
1.2 United States
2 Health effects
2.1 Associated problems
3.5 Genetic defects
6.2 Reading and magnification
6.4 Other aids and techniques
6.5.1 Adjusting attitude
6.5.3 Communication development
126.96.36.199 Social development
188.8.131.52 Language development
6.6 Healthcare access
8 Society and culture
8.1 Legal definition
8.2 Literature and art
8.2.2 Modern times
8.4 Metaphorical uses
10 Other animals
11 See also
13 External links
Snellen chart that is frequently used for visual acuity
The definition of visual impairment is reduced vision not corrected by
glasses or contact lenses. The
World Health Organization
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
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
Blindness is defined by the
World Health Organization
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.
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
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
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,
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).
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.
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
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
United States Congress
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.
Kuwait is one of many nations that share the 6/60 criteria for legal
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.
American Medical Association
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
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
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 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.
The most common causes of visual impairment globally in 2010 were:
Refractive error (42%)
age related macular degeneration (1%)
corneal opacification (1%)
diabetic retinopathy (1%)
The most common causes of blindness in 2010 were:
age related macular degeneration (5%)
corneal opacification (4%)
childhood blindness (4%)
refractive errors (3%)
diabetic retinopathy (1%)
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
Among working age adults who are newly blind in England and Wales the
most common causes in 2010 were:
Hereditary retinal disorders (20.2%)
Diabetic retinopathy (14.4%)
Optic atrophy (14.1%)
Congenital abnormalities (5.1%)
Disorders of the visual cortex (4.1%)
Cerebrovascular disease (3.2%)
Degeneration of the macula and posterior pole (3.0%)
Corneal disorders (2.6%)
Malignant neoplasms of the brain and nervous system (1.5%)
Retinal detachment (1.4%)
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
Glaucoma is a congenital and pediatric eye disease characterized by
increased pressure within the eye or intraocular pressure (IOP).
Glaucoma causes visual field loss as well as severs the optic
nerve. 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 causes: 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 cause and management from
the glaucoma developed by adults. 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.
The burden of onchocerciasis: children leading blind adults in Africa
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.
Re-educating wounded. Blind French soldiers learning to make baskets,
World War I.
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.
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
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.
Amblyopia: is a category of vision loss or visual impairment that is
caused by factors unrelated to refractive errors or coexisting ocular
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.
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. 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
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
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 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
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.
Scientists track eye movements in glaucoma patients to check vision
impairment while driving
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
American Medical Association provides an
approach to evaluating visual loss as it affects an individual's
ability to perform activities of daily living.
Screening adults who have no symptoms is of uncertain benefit.
World Health Organization
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.
Tommy Edison, a blind film critic, demonstrates for his viewers how a
blind person can cook alone.
Aside from medical help, various sources provide information,
rehabilitation, education, and work and social integration.
Folded long cane
A blind man is assisted by a guide dog in Brasília, Brazil
Blind girl feels shape of vehicle near Mana village, Uttarakhand
Visually impaired girl negotiating a rock while rock climbing
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
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.
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
RNIB in the United Kingdom.
Closed-circuit televisions, equipment that enlarges and contrasts
textual items, are a more high-tech alternative to traditional
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.
Access technology such as screen readers, screen magnifiers and
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
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
A tactile feature on a Canadian banknote
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
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
Some currencies' banknotes have a tactile feature to indicate
denomination. For example, the
Canadian currency tactile feature
Canadian currency tactile feature is a
system of raised dots in one corner, based on
Braille cells but not
It is also possible to fold notes in different ways to assist
Labeling and tagging clothing and other personal items
Placing different types of food at different positions on a dinner
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
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
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 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,
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
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.
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.
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 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 is also an important aspect of how blind or visually impaired
people perceive the world. Touch gives immense amount of information
in the person's 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.
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.
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 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.
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 their developing knowledge of the world, but rather their
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.
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
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.
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.
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.
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
Society and culture
List of blind people and Blind musicians
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 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.
Low vision is
sometimes used to describe visual acuities from 20/70 to 20/200.
Literature and art
Blindness in literature
The Moche people of ancient
Peru depicted the blind in their
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.
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?
Blind Woman by Diego Velázquez
The Sense of Touch by
Jusepe de Ribera
Jusepe de Ribera depicts a blind man holding a
marble head in his hands.
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
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 Trek's Geordi La Forge, who can
see with the aid of a VISOR, a fictitious device that transmits
optical signals to his brain.
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.
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
Main article: Visual prosthesis
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
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
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.
Main article: Blind 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
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.
Blindness and education
Recovery from blindness
Tangible symbol systems
Visual impairment due to intracranial pressure
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V · T · D
ICD-10: H54.0, H54.1, H54.4
Wikimedia Commons has media related to Visual impairment.
Blindness at Curlie (based on DMOZ)
Chisholm, Hugh, ed. (1911). "Blindness". Encyclopædia
Britannica (11th ed.). Cambridge University Press.
Eye Conditions (RNIB)
Center for the Partially Sighted Low Vision Information and Resources
Diseases of the human eye (H00–H59
Thygeson's superficial punctate keratopathy
Pellucid marginal degeneration
Terrien's marginal degeneration
Persistent pupillary membrane
Ocular ischemic syndrome / Central retinal vein occlusion
Central retinal artery occlusion
Bietti's crystalline dystrophy
Central serous retinopathy
Epiretinal membrane (Macular pucker)
Vitelliform macular dystrophy
Leber's congenital amaurosis
Glaucoma / Ocular hypertension / Primary juvenile glaucoma
Leber's hereditary optic neuropathy
Persistent fetal vasculature / Persistent hyperplastic primary
Persistent tunica vasculosa lentis
Familial exudative vitreoretinopathy
Foster Kennedy syndrome
Optic disc drusen
Toxic and nutritional
Chronic progressive external ophthalmoplegia
Esotropia / Exotropia
Conjugate gaze palsy
One and a half syndrome
Anisometropia / Aniseikonia
Leber's congenital amaurosis
Blindness / Vision loss / Visual impairment
Argyll Robertson pupil
Marcus Gunn pupil