blindness

from Wikipedia, the free encyclopedia

Classification according to ICD-10
H54 Blindness and poor eyesight
ICD-10 online (WHO version 2019)
Glance into a lively shopping arcade with brightly lit shop windows and a mirror-smooth, light stone floor.  A slim, attractive man of about forty comes towards us casually.  He has full, dark hair, wears black trousers, a fashionable, dark gray striped, long-sleeved shirt and very dark sunglasses with glare shields pulled around to the sides.  He leads a yellow Labrador Retriever wearing a blue bandana on a guide dog harness.  Two young women diagonally to the left behind the two look at the team with interest.
Blind man with his guide dog

Under blindness is defined as the prominent form of visual impairment with entirely absent or only extremely low existing visual perception of one or both eyes . It can be congenital (birth blindness) or acquired. The prospects of an improvement or even a cure are low , depending on the onset of the disease, causes and - especially in third world countries - general access to appropriate treatment offers. That being said, there are a number of diseases for which there is no effective therapeutic approach and which are therefore considered incurable. If blindness affects both eyes, it is a severe disability , for which, according to German law, there is a fundamental right to assistance in the form of blindness allowance . It is regulated in the respective state blind allowance law or as assistance for the blind in the Social Security Code (SGB XII § 72).

Definitions

Degree of disability

Seeing on the better eye in each case
(with optimal correction)

blind

Visual acuity up to a maximum of 0.02 or
tubular field of view up to a maximum of 5 ° or
graded mixed forms

highly visually impaired VA between 0.02 and 0.05
visually impaired VA between 0.05 and 0.3

In Germany , according to the statutory provisions and health care guidelines, a person is considered to be blind if their visual acuity in the better eye is no more than 1/50 = 0.02 even with optimal glasses or contact lens correction (somewhat misleadingly referred to as "2% or less"), or if there are other permanent visual impairments that can be equated with this impairment. According to the German Ophthalmological Society (DOG), this applies, for example, to the concentric restriction of the outer field of view limits to a maximum of 5 degrees (tubular field of view ) . Color blindness (achromatopsia) and night blindness (hemeralopia) do not belong to blindness in this sense .

To illustrate: A visual acuity (visual acuity) of 1/50 = 0.02, which represents the limit to blindness with entitlement to blindness allowance, means that the currently readable optotypes have 50 times the reference size of 5 minutes of visual angle . This is 4.17 degrees of viewing angle, which corresponds to a font size of 2.2 cm at a reading distance of 30 cm.

A reduction in visual acuity to less than 0.3 in the better eye is called a visual impairment. As a highly visually impaired is a person who does not have the best seeing eye with optimum correction merely a visual acuity of more than 1/20 = 0.05.

The definition of blindness or visual impairment always takes place in the legal sense with reference to the affected “person” and not to the eye as “organ”. In contrast, visual impairments, severe visual impairments and blindness can also occur unilaterally with the limit values ​​mentioned in each case - with normal visual performance of the healthy eye. Although this results from the medical point to a single lens reflex (monocular) visual impairment or blindness, but the person in question does not apply in the legal sense as a blind or visually impaired, so here in the adoption of an adequate orientation assets despite practical monocular vision is also not entitled to benefits.

Amaurosis

Compared to the term “blindness”, the medical term amaurosis exclusively describes the complete lack of light perception in one or both eyes when there is a loss of any optical stimulus processing (complete blindness).

Causes and Spread

The colored graphic shows the frequency distribution of the causes of blindness in Germany in 2002 in a pie chart. At first glance, the most common causes stand out: 50% age-related macular degeneration, then - together around another third - 18% glaucoma and 17% diabetic retinopathy .  The remainder is shared by cataracts (5%), corneal opacity (3%), blindness in childhood (2.4%) and other causes (4.6%).
Causes of blindness in Germany

In principle, any disruption of a structure of the visual system can lead to blindness.

Another cause of blindness can be the mutation of the Mark3 gene . Altering this gene prevents the eyes from fully developing and causes structural changes and visual impairment in humans.

According to the 2004 WHO report, 164,000 (0.2%) blind and 1,066,000 (1.3%) visually impaired people live in Germany . In Germany around 10,000 people go blind every year (incidence 12.3 / 100,000) and around 160 children are born blind (2 out of 10,000). While there was only a moderate increase in blindness of 9% between 1990 and 2002, an increase in visual impairment of 80% was registered. This is mainly due to the increased life expectancy . While optic atrophy is the most common cause of blindness in people up to 39 years of age, diabetic retinopathy in the 40 to 79 year old age group and age-related macular degeneration from the age of 80 , followed by glaucoma . Since 48% of all blindness occurs from the age of 80, age-related macular degeneration is the most common cause of blindness in Germany. 68% of all new blindnesses affect women. The main reason for this is probably that women are disproportionately represented in this age group due to their much higher life expectancy.

Further difficulties and impairments

Blindness always goes hand in hand with a limitation of spatial orientation . However, this can be expanded in an acoustic and tactile manner. A number of blind-specific aids make daily life easier, but these can lead to a certain degree of dependence in several ways. An independent, self-reliant lifestyle is the goal of most of those affected; however, a relative need for help often remains. A lack of educational resources, career opportunities , reduced autonomous mobility and social contacts often lead to problems that can be expressed in social withdrawal. These circumstances are often reinforced by a public image that often appears to be shaped by prejudice and ignorance.

An infrastructural, social and cultural opening towards the needs of people who are visually impaired is important for all people. A role model for this is the city of Marburg with the local university for the blind , which has been providing exemplary support and training for people who are blind or visually impaired for decades. It is important not only to have appropriate aids such as traffic lights with acoustic signals or menus in Braille , but also to implement a consistent inclusion of all people from the beginning and the inclusion of different needs in the entire infrastructural, social, cultural and urban structure of a city.

Training, media and resources

advancement

Since therapeutic options often do not exist in cases of blindness, specific training measures ( rehabilitation ) are of great importance. The main aim here is to enable blind people to lead an independent and responsible lifestyle, which is generally perceived as a higher quality of life.

For blind and visually impaired children in particular, early intervention that starts immediately after birth is of crucial importance. Later this should be continued either within the framework of specialized kindergartens and special schools , or integrated in regular kindergartens and schools. Early intervention is a secure prerequisite for successfully shaping the intellectual development, independence and professional opportunities of a person who was born blind or went blind early.

See also: Deutsche Blindenstudienanstalt , Blindenanstalt Nürnberg , Nikolauspflege , Berufsförderungswerk Würzburg , Blindeninstitutsstiftung , Other See

media

The 1825 by Louis Braille developed Braille, known as Braille , blind people allows reading and writing of texts. Other Braille systems have been almost completely superseded by Braille. Writing texts is z. B. possible with a braille machine like the Perkins Brailler . The first typewriter for braille was invented in 1899 by Oskar Picht . Today there are also Braille displays and Braille printers for the PC .

Libraries for the blind and non-profit associations produce and lend books, magazines and texts in audio and braille format. In the German-speaking countries , these libraries and associations have come together to form the media community for blind and visually impaired people , or Medibus for short. There are only thirteen children's books available as tactile picture books, learning books or non-fiction books for preschool children in German-speaking countries. In addition, there are few slide collections in files. The most widespread lending medium are phonograms. Shipping is postage-free as a blind item . In the past, audio books and audio magazines were rented out on compact cassettes , which are now obsolete , but between 2004 and 2010 they switched to CDs in the DAISY format . DAISY is the name of a global standard for navigable and barrier-free accessible multimedia documents. The abbreviation DAISY stands for "Digital Accessible Information System". Commercial audio books also give blind people access to literature .

The public television channels in Germany and the streaming service Netflix broadcast films in two-channel sound , in which the story is told on the second channel via audio description . This method is also used in cinema films, often through headphones; it is then referred to as an audio film . Films with audio description can also in cinema be consumed together with seeing if for the sound track of audio description in the smart phone - app exists Greta. The smartphone uses the microphone to orient itself to the current film and then synchronizes the soundtrack of the audio description, which the blind cinema -goer can listen to using bone conduction headphones or in-ear headphones.

Tactile graphics on swell paper and tactile maps help blind people to “understand” images and spatial relationships. In well-known buildings , old towns and museums , tactile models of the system or building are sometimes set up.

In addition, some local radio stations in German-speaking countries broadcast regional news for the visually impaired, with local newspapers being read to them. In English-speaking countries in particular, there is also the so-called Radio Reading Service (German: Radio-Vorlese-Dienst), in which news and literature are often read live for the visually impaired throughout the day. Some of these services can also be received via live stream from us over the Internet. The podcast has established itself as a popular medium for entertainment and information exchange over the Internet.

Computer usage

Blind people can operate computers with the help of so-called screen reader software for Windows such as COBRA or JAWS or the free NVDA and for Apple computers with VoiceOver already integrated in the system . Screen readers are also available for smartphones based on the Google Android and Apple iOS operating systems and thus offer the option of using communication and navigation software on the go. The screen content and the controls are read out by a voice output or output in braille on a Braille display . The PC keyboard is used to write with the ten-finger system and navigation is carried out using key combinations and the cursor keys instead of a mouse. Texts printed on paper, such as books and letters, can be read with a scanner and text recognition software . Blind internet users depend on the design of websites that are easy to access .

Since many people only go blind in old age and have difficulties learning to use a PC, there are special reading systems with which printed texts can be easily recorded, saved and read out.

mobility

Blind man crossing a pedestrian crossing with a long stick

After an orientation and mobility training (O&M), blind people can find their way around their environment fairly independently. A similar offer exists for the area of ​​practical life skills (LPF). The correct use of a white long stick protects against collisions and falls and can provide valuable information for orientation at close range, as can hearing and the sense of smell . From birth, blind people here have a certain advantage over later blinded, most likely because they sure neural capacities of the visual cortex ( visual cortex allowed to use) in the brain: These so-called active. Human echolocation is seeing with the eyes mimic part.

Early intervention

For the successful development of a child who was born blind, it is of crucial importance to 'go through' all stages and phases of development in an age-appropriate manner, analogous to sighted children. Most of the time, children who are visually impaired or blind need targeted support during the sensitive phases , as otherwise a development comparable to that of sighted children may be threatened. In addition, the ability for passive and active echolocation should be improved through early and regular training, but it represents only one aspect of the targeted support of children who are blind or visually impaired: The promotion of perception generally plays the central role in the early support of children Children with sensory disabilities, especially the promotion of spatial understanding. A pioneer in this field is the Danish psychologist Lilli Nielsen , who has been researching and publishing scientifically in this field for decades and has also developed related funding materials. Since 2011, the blind developmental psychologist and special education teacher Daniel Kish has been receiving media attention in Germany , who has also developed training plans for small children that are intended to represent a new standard in early intervention and mobility training .

Animals

Blind people can orientate themselves much better on familiar paths or in familiar terrain than in completely unknown surroundings. Guide dogs lead their owners on the optimal path and avoid obstacles. On command, you search for and find individual destinations such as traffic light posts, mailboxes, house entrances or free seats on public transport.

There are attempts to train horses of the Falabella breed to be guide animals for the blind. Some of the animals are already in use.

Satellite navigation

Satellite-based navigation and spatial information systems that can be used with blind-operated mobile devices represent a great opportunity to improve mobility and quality of life for blind people. The first satellite-based navigation aids in German-speaking countries were the free software Loadstone-GPS and the commercial product Wayfinder Access utilized. The free program runs on high-quality Nokia cell phones that can be operated by blind people using screen reader software. The information on the screen is output from a voice output through the loudspeaker. In addition to navigation systems such as Kapten Plus or Trekker Breeze, there are some apps for smartphones such as the Apple iPhone that can be used by blind people using screen readers such as VoiceOver .

Tactile ground guidance systems

The yellow plastic floor panels (outside right) are on all footpaths in Tokyo with different knobs in front of branches, stairs, crossings, etc.

Floor indicators such as grooved and knobbed pavement are intended to help blind long-pole users find their way around and navigate in squares, streets, sidewalks and in train stations or other public buildings. If, in addition to these tactile marking strips , other aids such as lettering in Braille and voice announcements are provided in elevators, this is known as a guidance system for the blind . Traffic lights with acoustic or vibrating signals and properly secured construction sites and floor openings make participation in road traffic less dangerous for blind pedestrians .

Identification

Three black dots on a yellow background
The three black dots on a yellow blindfold

Main article: Marking for visually impaired and blind people (Austria), White Cane Day

Like everyone who can only move safely in road traffic to a limited extent due to physical impairments, blind or severely visually impaired pedestrians are only allowed to drive on public roads in Germany if they have taken precautions not to endanger other road users. You can fulfill your duty of care by marking your handicap with a white cane for the blind, with a yellow badge, in particular an armband with three black dots and / or by accompanying a guide dog in a white harness. This saves other road users from otherwise generally justified trust that they will see and observe the traffic signs, for example, and at the same time require them to be particularly careful. There is no legal obligation to use specific labeling. Other road users are not allowed to use such license plates in traffic.

General resources

Electronic colorimeter for the visually impaired and blind with voice output via a loudspeaker
A somewhat old-fashioned blind watch lies on a light brown cloth. It has a link bracelet made of light metal and a round brass case with a crown. The white dial is covered with a domed glass lid, which is set in a brass ring. The lid was flipped up so that the dial is now exposed. It shows the numbers 1 to 12 in an inner circle in black, Arabic numerals; in an outer ring, the positions of these numerals can be felt by protruding, point-shaped pens. There are three points for the 12; two points each for 3, 6 and 9; the remaining digits have a point. The black pointers line the black numbers and the dots, they show one minute to two o'clock.

There are many different aids for everyday life .

It starts with simple things like tactile or talking clocks, dictating machines , bill acceptors or Münzsortierboxen for the independent handling of cash and proceeds adjusted household appliances such as a microwave oven with speech to speaking measuring cups , scales , colorimeters , fever thermometers , blood pressure or blood glucose meters for Diabetics and small electronic devices for labeling objects such as compact disks with barcode or RFID labels, each with its own voice recording. Skat cards that are covered with a plastic film have been around for some time , so that sighted people can play as usual and blind people can feel the cards at the same time. An election template enables independent participation in political elections.

School tools

In order for a blind child to participate successfully in school, various aids are required. Some important aids for the blind that are important in school: Braille display , screen reader, braille machine , swell paper machine, speaking scales, speaking thermometer , tactile clock, compass for the blind, dice for the blind to feel, tactile rulers and measuring tapes, basic geometric shapes, tactile maps, tactile globe, bell ball for exercise and sport.

Others

Blind people usually have an above-average sense of touch . This special ability is used for the early detection of breast cancer . As part of in North Rhine-Westphalia settled model project "Discovering hands" (discovering hands) was the training course created the Medical Tastuntersucherin.

Sleep disorders in blind people

In the case of blind people who cannot perceive the light-dark change, circadian sleep-wake rhythm disturbances of the free-running rhythm type and other sleep-wake rhythm disturbances often occur , since the synchronization of the circadian rhythm, which is popularly known as the "internal clock" due to the light-dark alternation timer not working properly.

Simulated blindness experiences for sighted people

View from above on a bronze relief, which shows the old town of Münster as a model.  It is mounted horizontally on a base in the pedestrian zone of Münster's old town at about waist height.  You can only see the hips of the passers-by standing close behind; some feel the details of the model with their hands.  This shows slightly stylized streets, squares, buildings and groups of trees;  the houses are about 2 cm high.  The cathedral, the Lamberti and the Liebfrauenkirche stand out clearly with a height of several centimeters.  The streets are marked with their names in Braille.  On the right edge of the picture you can see parts of a dedication;  this multi-line text is in Braille as well as in raised normal script.
Relief city map on Domplatz in Münster , also available on Lamberti and Überwasserkirchplatz depending on the area

Experience spaces such as the exhibition Dialogue in the Dark , the Dialogue Museum or dark restaurants offer sighted people in a protected environment an opportunity to experience blindness for themselves .

In blind fold blindness is simulated. Also in connection with masking or customs when using a mask . Blindness was symbolized in ritual games .

Blindness in language, art and literature

The portrait-format oil painting from 1856 shows a bright yellow cornfield;  in front of it, in the foreground facing the viewer, are two girls.  Immediately behind the girls, a small stream flows across the picture.  The cornfield extends behind the brook far to the rear and there up a hill to its summit;  there are the houses of a village between the trees.  In the field you can see cattle and a few crows.  The sky above, in the upper fifth of the picture, is a thundery gray, in the middle on the hill a double rainbow rises, which leads out of the picture to the top right.  It's the mood after a thunderstorm.  The two girls wear sack-like clothes made of coarse linen in shades of brown and blue that is worn in many places.  The older of the two, sitting on the left, around 16 years old, is blind.  She has thrown a short brown coat over her head for protection.  Below you can see her straight, red hair parted in the middle.  She has raised her head and is enjoying the warm rays of the sun on her face, relaxed and with her eyes almost completely closed.  On her lap is a small accordion, around her neck, only recognizable on closer inspection, is a small sign with the words "PITY THE BLIND" (for example: "Have mercy on the blind").  The two are beggars.  The younger, blonde girl - presumably her sister - has nestled very close to the left side of the older woman;  she has taken the little sister's hand with her left hand and is holding her tight.  The younger one has pulled part of the coat over her head and looks anxiously around to the rear, where lightning and thunder probably rumbled only recently.
Painting "The Young Blind One" by John Everett Millais

Blindness often appears as a motif in myths , narratives and pictorial representations of all kinds. The legendary Greek seer Teiresias and the old Oedipus should be mentioned . In 1568, Pieter Brueghel the Elder addressed the parable of the fall of the blind ("But if one blind man leads the other, they both fall into the pit", Mt 15:14 ) in his picture The fall of the blind . John 9:25 tells of the miraculous healing of a blind man through Jesus Christ . The painter El Greco took up the cure; Blindness is also a theme in John Newton's famous song Amazing Grace . Lena Valaitis took part in the Eurovision Song Contest in 1981 with Johnny Blue , a song about a blind boy who is learning to play the guitar . 1986 sang The Puhdys Born Blind .

Likewise, the blind are at the center of literary works (e.g. in Vladimir Nabokov's novel König Dame Bube , José Saramago's novel Die Stadt der Blinden or in Mein Name sei Gantenbein by Max Frisch ). In addition, the novel The Scent of Women and its film adaptations as well as the film Peas at 5:30 am are about life with blindness.

Saint Odilia (Ottilie) and Saint Lucia of Syracuse are venerated as patron saints of the sight and the blind.

Blind cow is a parlor game that is almost exclusively played by children and has its origins in the 15th century.

Duds are ammunition such as grenades or bombs that have not exploded or not fully exploded after being used ( fired ordropped). The term is also used colloquially as an insult .

In a figurative sense, seeing often stands for the ability to perceive reality at all. The same metaphor applies to the lack of the two skills:

  • “I want to keep an eye on the matter” or “I want to keep an eye on it” means: I want to ensure that the matter progresses satisfactorily.
  • “Love is blind” means: whoever loves does not recognize the beloved as he or she really is.
  • “I have to open my eyes to him.” Means: I want to explain to him what is really happening and what it is related to.
  • If something is absolutely clear, the folksy say coarse: "A blind man with a cane can see that."
  • “Among the blind, the one-eyed man is king” - even something or someone with actually only below average qualities in one area outperforms others who do not have such qualities at all.
  • “Someone is politically blind or blind to reality” means that they do not understand the connections in politics or reality.

Criticism of the blindness metaphor

"They were blind in the right (or left) eye" indicates a partisan attitude, which tends towards tolerance and forbearance towards the political "right" (or "left").

There has been criticism of this blindness metaphor from both the disabled and the Auschwitz Committee in the Federal Republic of Germany. V.

Socio-economic costs

Blindness means a serious limitation in mobility, communication and access to information. Accordingly, the follow-up costs of blindness are immense and, according to an investigation, can amount to an average of over EUR 90,000 per blind adult patient. Costs arise from direct medical expenses, aids such as guide dogs and the non-medical costs for, for example, adapting the apartment, care allowance, lost work time, etc.

See also

literature

  • Wolfgang Drave, Hartmut Mehls (Hrsg.): 200 years of blind education in Germany (1806-2006). edition bentheim, Würzburg 2006, ISBN 3-934471-57-9 .
  • Kai Nonnenmacher: The black light of modernity: on the aesthetic history of blindness. Niemeyer, Tübingen 2006, ISBN 3-484-63034-5 (Dissertation University of Mannheim 2003, XI, 377 pages).
  • Eva M. Glofke-Schulz: Lioness in the jungle. Blind and visually impaired people between stigma and becoming themselves . Psychosozial-Verlag, Giessen 2007, ISBN 978-3-89806-735-5 .
  • Oliver Häuser, Stefanie Krug: Seeing people. 150 years of St. Nicholas care. (1856-2006). Nikolauspflege, Foundation for the Blind and Visually Impaired People, Stuttgart 2006, ISBN 3-00-018633-6 (142 pages in large print with numerous illustrations).
  • Otto Käfer: Blindness in Art. Representation and imagery . Gebrüder Mann Verlag, Berlin 2016, ISBN 978-3-7861-2758-1 (dissertation, Eberhard Karls University of Tübingen, 2014, 460 pages).
  • Jacques Lusseyran : The rediscovered light. The life story of a blind man in the French resistance (= dtv 30009 non-fiction book ). 4th edition. Deutscher-Taschenbuch-Verlag, Munich 1992, ISBN 3-423-30009-4 .
  • Heinrich Scholler: Encyclopedia of the blind and visually impaired system . Müller, Heidelberg 1990, ISBN 3-8114-2188-3 , pp. 516 .
  • Josephine Siebe : Modern care for the blind. With six illustrations based on original photographs. In: Reclam's universe. Modern Illustrated Weekly , January 27, 1911, pp. 571-574.

Web links

Wiktionary: Blindness  - explanations of meanings, word origins, synonyms, translations
Commons : Visually Impaired  - Collection of pictures, videos, and audio files

Individual evidence

  1. Social Code Book Twelfth (SGB XII) - Social Welfare - § 72 Help for the Blind
  2. Bavarian Blindengeldgesetz. What is blindness according to the BayBlindG ( Memento from December 11, 2005 in the Internet Archive )
  3. ↑ Reference points for the expert activity no. 23 Blindness and severe visual impairment with further example cases
  4. ^ Pschyrembel clinical dictionary . With clinical syndromes and nouns anatomica. = Clinical Dictionary. Edited by the publisher's dictionary editor under the direction of Christoph Zink. 256th, revised edition. de Gruyter, Berlin a. a. 1990, ISBN 3-11-010881-X .
  5. Muhammad Ansar, Hyunglok Chung et al. a .: Visual impairment and progressive phthisis bulbi caused by recessive pathogenic variant in MARK3. In: Human Molecular Genetics. 27, 2018, p. 2703, doi : 10.1093 / hmg / ddy180 .
  6. ↑ Achieve equal opportunities
  7. Concrete situation of blind and visually impaired people on the primary job market, in special 5: DVBS guide to social policy ( memento from March 9, 2016 in the Internet Archive )
  8. Disabled at work: Blind, not stupid, FAZ from October 23, 2008
  9. Acoustic orientation and mobility
  10. Horst Köhler for joint teaching of disabled and non-disabled children
  11. Internationaler Audiodienst (iad) Blindenstadt Marburg
  12. History and tasks of the media community for blind and visually impaired people e. V. (Medibus) ( Memento from December 24, 2008 in the Internet Archive )
  13. Books for blind children
  14. Smartphone app for audio description in the cinema
  15. Laurent A. Renier, Irina Anurova, Anne G. De Volder, Synnöve Carlson, John VanMeter, Josef P. Rauschecker: Preserved Functional Specialization for Spatial Processing in the Middle Occipital Gyrus of the Early Blind. In: Neuron. Vol. 68, 2010, pp. 138-148, doi: 10.1016 / j.neuron.2010.09.021 .
  16. Active human echolocation (click sonar)
  17. How blind people orient themselves using echolocation (click sonar)
  18. ^ [1] The development stage model according to Piaget
  19. Acoustical awareness
  20. ^ Steffen Zimmermann: Klicksonar workshops in Berlin with Daniel Kish | Other Seeing eV for the promotion of blind children. Retrieved October 6, 2019 (German).
  21. Progressive support for blind children
  22. ^ Spiegel-Online: With the miniature horse in the lecture hall
  23. Product information at INCOBS
  24. Description of the MyWay app for the blind on the Voice Over Portal ( Memento from May 13, 2012 in the Internet Archive )
  25. German description of the BlindeSquare app on KuUBuS
  26. § 2 Paragraph 1 Driving License Ordinance (FeV), there is a risk of a fine in the event of disregard according to § 75 No. 1 FeV
  27. § 2 Paragraph 2 FeV
  28. Administrative offense according to § 75 no. 2 in conjunction with Section 2 Paragraph 3 FeV
  29. S3 guideline for non-restful sleep / sleep disorders of the German Society for Sleep Research and Sleep Medicine (DGSM). In: AWMF online (as of 2009)
  30. http://leidmedien.de/aktuelles/sichtweise/blinde-kuh-trifft-taube-nuss-metaphern-der-beherung/
  31. http://www.stiftung-auschwitz-komitee.de/system/files/intern/dokumente/AK_Erkl%C3%A4rung%20rechtes%20Auge.pdf
  32. PSS16 Cost of Blindness in Austria , Institute for Pharmaceutical Economic Research Vienna, accessed on December 3, 2015