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Snellen chart

Purpose

Snellen chart is used to estimate visual acuity (last three rows are 20/15, 20/13 and 20/10)

A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen, who developed the chart in 1862. Many ophthalmologists and vision scientists now use an improved chart known as the LogMAR chart.

Snellen developed charts using symbols based in a 5×5 unit grid. The experimental charts developed in 1861 used abstract symbols. Snellen's charts published in 1862 used alphanumeric capitals in the 5×5 grid. The original chart shows A, C, E, G, L, N, P, R, T, 5, V, Z, B, D, 4, F, H, K, O, S, 3, U, Y, A, C, E, G, L, 2.

The normal Snellen chart is printed with eleven lines of block letters. The first line consists of one very large letter, which may be one of several letters, for example E, H, or N. Subsequent rows have increasing numbers of letters that decrease in size. A person taking the test covers one eye from 6 metres or 20 feet away, and reads aloud the letters of each row, beginning at the top. The smallest row that can be read accurately indicates the visual acuity in that specific eye. The symbols on an acuity chart are formally known as " optotypes".

In the case of the traditional Snellen chart, the optotypes have the appearance of block letters, and are intended to be seen and read as letters. They are not, however, letters from any ordinary typographer's font. They have a particular, simple geometry in which:

the thickness of the lines equals the thickness of the white spaces between lines and the thickness of the gap in the letter "C"

the height and width of the optotype (letter) is five times the thickness of the line.

Only the nine letters C, D, E, F, L, O, P, T, Z are used in the common Snellen chart. The perception of five out of six letters (or similar ratio) is judged to be the Snellen fraction. Wall-mounted Snellen charts are inexpensive and are sometimes used for approximate assessment of vision, e.g. in a primary-care physician's office. Whenever acuity must be assessed carefully (as in an eye doctor's examination), or where there is a possibility that the examinee might attempt to deceive the examiner (as in a motor vehicle license office), equipment is used that can present the letters in a variety of randomized patterns. BS 4274-1:1968 (British Standards Institution) "Specification for test charts for determining distance visual acuity" was replaced by BS 4274-1:2003 "Test charts for clinical determination of distance visual acuity - Specification". It states that "the luminance of the presentation shall be uniform and not less than 120 cd/m ². Any variation across the test chart shall not exceed 20 %." According to BS 4274-1:2003 only the letters C, D, E, F, H, K, N, P, R, U, V, and Z should be used for the testing of vision based upon equal legibility of the letters.[citation needed ]

Visual acuity = Distance at which test is made / distance at which the smallest optotype identified subtends an angle of five arcminutes.[citation needed ]

"6/6"(m) or "20/20"(ft) vision

Snellen defined "standard vision" as the ability to recognize one of his optotypes when it subtended 5 minutes of arc. Thus the optotype can only be recognized if the person viewing it can discriminate a spatial pattern separated by a visual angle of one minute of arc.

Outside the United States, the standard chart distance is 6 metres (20 ft), and normal acuity is designated "6/6". Other acuities are expressed as ratios with a numerator of 6. Some clinics do not have 6-metre eye lanes available, and either a half-size chart subtending the same angles at 3 metres (9.8 ft), or a reversed chart projected and viewed by a mirror is used to achieve the correct sized letters.

In the most familiar acuity test, a Snellen chart is placed at a standard distance: 6 metres. At this distance, the symbols on the line representing "normal" acuity subtend an angle of five minutes of arc, and the thickness of the lines and of the spaces between the lines subtends one minute of arc. This line, designated 6/6 (or 20/20), is the smallest line that a person with normal acuity can read at a distance of 6 metres. This definition is arbitrary, since human eyes typically have higher acuity, as Tscherning writes, "We have found also that the best eyes have a visual acuity which approaches 2, and we can be almost certain that if, with a good illumination, the acuity is only equal to 1, the eye presents defects sufficiently pronounced to be easily established."

Three lines above, the letters have twice the height of those letters on the 6/6 (or 20/20 in the US) line. If this is the smallest line a person can read, the person's acuity is "6/12" ("20/40"), meaning that this person needs to approach to a distance of 6 metres (20 ft) to read letters that a person with normal acuity could read at 12 metres (39 ft). In an even more approximate manner, this person could be said to have "half" the normal acuity of 6/6.

At exactly 6 metres' distance from the patient, the letters on the 6/6 line shall subtend 5 minutes of arc (such that the individual limbs of the letters subtend 1 minute of arc), which means that the chart should be sized such that these letters are 8.73 mm tall and the topmost (6/60) "E" should be 87.3 mm tall. Putting it another way, the eye should be at a distance 68.76 times the height of the top (6/60) letter. The formula is

where is the optotype height or width (which are the same due to the optotype being on a square grid), is the distance from eye to chart, and is the angle subtended by the optotype, which is 5 arcminutes as specified by Snellen.[6] Another calculation for United States clinics using 20-foot chart distances (slightly more than 6 m), and using a 17 mm model eye for calculations, and a letter which subtends 5 minutes of arc, gives a vertical height of the 20/20 letter to be 8.75 mm.[7]

Acuity charts are used during many kinds of vision examinations, such as "refracting" the eye to determine the best eyeglass prescription.

The largest letter on an eye chart often represents an acuity of 6/60 (20/200), the value that is considered "legally blind" in the US. Many individuals with high myopia cannot read the large E without glasses, but can read the 6/6 (20/20) line or 6/4.5 (20/15) line with glasses. By contrast, legally blind individuals have a visual acuity of 6/60 (20/200) or less when using the best corrective lens.

To ensure adequate illumination of the Snellen charts, various medical device manufacturers had developed Snellen chart products with backlight or projection.

Since computer monitors typically have good lighting for reading and LCD/LED monitors have high DPI (between 96 and 480) they are suitable for displaying optotypes. Commonly digital chart products support randomizing optotypes displayed to prevent patients from cheating through memorizing the chart. In Google Play and App Store (iOS), there are Snellen chart apps for smart phones and tablets.

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Snellen chart Purpose Snellen chart is used to estimate visual acuity (last three rows are 20/15, 20/13 and 20/10) A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen, who developed the chart in 1862.

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Making Sensuous Knowledge: The Practice of Aaron McPeake
Marsha Bradfield

How to make sense of our lives? If you're inclined to take this as a moral question, don't. It doesn't ask how we should or ought to live. It wonders how we understand our experience of being. We can think of this as a kind of sensuous knowledge. It's the day-to-day practice of reflecting meaning in and out of existence despite the creeping conviction that to the question, 'What is the meaning of life?' there is, in all likelihood, no satisfying response.

We've come to expect critical contemporary art to tarry with existential issues. Yet the practice of Aaron McPeake doesn't instruct us on reconciling the apparent meaninglessness of this absurd world and, indeed, McPeake is unlikely to see himself as addressing such a grandly intractable concern. His interest in producing sensuous knowledge seems to spring from a different desire: to offer us compelling encounters with forms and materials in throes of transformation. McPeake's videos document bronze pouring, ice melting, shadows recast as silhouettes, while many of his sculptures only find full expression when struck or otherwise engaged, literally. This approach is physical and direct in ways that render McPeake's art deeply experiential. It reminds us we're alive.

McPeakes came to visual art through a career of lighting design for the stage: opera, plays and other dramatic performances. His recent work retains an interest in transforming the ordinary into the extraordinary through technological means, lighting among them. Whatever the process or medium, though, a sense that 'matter' matters preoccupies this art-though it's more than 'stuff n' things' that undergo change in McPeake's work. At its best it elicits an existential identification, prompting us to meditate on our own being in flux. As McPeake's artworks pull and hold us, their embrace seemingly guided by a desire for sustained encounter, they remind us that although always changing, we're not alone. Change, in fact, is something we hold in common. McPeake's art goes the distance to meet our personal need to feel as though our change-what happens to us-matters.

The phrase 'our personal need' shares with McPeake's art the possibility of striking a balance between the subjective and the objective as different but interdependent modes of making sense, of gaining sensuous knowledge, of self and beyond.

It's so easy to succumb to lopsided views of who we are. For some, it's all about 'me': my feelings, my issues, my challenges and my accomplishments. Whether good times or bad, 'You couldn't possibly understand because they're happening to me'.

For others it's all about 'us': our shared needs based on what's required for each to survive. In extreme cases 'me' supplicates to the collective will. Rolling over, 'me' decants the individual subject as the ''m' turns into the 'w' and 'me' becomes 'we'. The result? 'We stand in solidarity' but also, 'We are the only hope against them'. There are many reasons why 'us/them' is a central organising principle of the post-millennial zeitgeist but there is one that is core. With the whittling of the welfare state and the dominance of neoliberalism, there are no guarantees that 'our personal need,' however modest, will be met, either now or in the future, because here's the thing: the needs of others, a select few, may well matter more. Equally in art: Whose needs take priority? What balance is required between meeting those of the artist in their practice and the needs of others, those encountering artworks, later, sometimes decades after they're produced and in contexts incognita: the slipstream of becoming.

If the coupling of these concerns strikes you as odd then you don't know the practice of Aaron McPeake. One aspect of his post-conceptual approach is this: McPeake demonstrates ways to accept and live with, indeed to embrace, the complementary positions of self and other and now and later, in art as in life. He does this not with reference to politics or theory per se, which should not suggest his practice isn't either critical or political. It's rather the case that McPeake engages with matter in a way that sublimates the conceptual into sensuous encounter and in the process, (just) makes good sense.

This sensuous knowledge features in the body of work that McPeake produced as the 2013 recipient of the Adam Reynolds Memorial Bursary. This award 'aims to support a mid-career artist or artists, looking to develop their artistic practice and build their profile...' ¹. What this description doesn't mention, though, is that Adam Reynolds died of muscular dystrophy after a distinguished but too brief career in contemporary art. Suffice it to say that Nicholas Serota, Director of Tate, wrote his obituary.

McPeake's own disability isn't obvious when you meet him or encounter his artworks; the artist is legally blind. In 2002 he abandoned lighting design and returned to teaching and practicing art. A decade later he completed his PhD at Chelsea College of Arts, his thesis exploring the impact of lost vision on the visual artist and is poetically titled, Nibbling at Clouds - The Visual Artist Encounters Aventitious Blindness ². Whilst the written aspects of McPeake's doctoral project examine the apparent paradox explicitly and at length, the practical one-his artworks-engage with what it means to be a blind visual artist more obliquely.

A generous and inclusive approach, the artist's commitment to working in ways that although deeply informed by his personal experience also transcend 'blindness', manifest in the body of work he produced for the Adam Reynolds award. For McPeake, this three-month residency at Spike Island (Bristol) was an opportunity for intense and experiential learning. There were materials. There were facilities. There were technicians. There were other residents with skills to exchange: a community of practice. These things mix together in a potent cocktail that for many artists is more powerful than drugs and definitely more productive than porn.

For McPeake this played out as a series of 'learning episodes'. Auto-didacticism drives the artist, often compulsively, to experiment with material techniques and modes of understanding that buck convention. In the supportive context of Spike Island, a counter-intuition took shape: active unlearning through intentional practice. For instance, McPeake experimented with slate, trying to unlearn how to write. He was the first generation in his family not to master his ABCs on this fine-grained, foliated, heterogeneous metamorphic rock. To reference this historic break while anticipating the nearly-here future, the artist produced a cool and unapologetic keyboard made from an amalgam of slate dust that was pressed out of a mould. This sensuous object comes from an age when penmanship has gone the way of the dodo bird. Because there is only typing, children master shifting between numbers and symbols instead of the loopty loops of cursive script.

But McPeake also experimented with this technology from a bygone era. He tried writing and drawing on slate with chalk and as a child, a hankering for lost innocence that went unsated. Neither working blindfolded, nor left-handed, nor on his knees-none of these limitations helped the artist to either forget or productively unlearn. By his own admission, the renderings he produced looked, well, naff. One would expect this to be disappointing but that's not how McPeake describes it. These shortcomings were less cause for concern than hard won celebration, evidence the artist was operating outside his field of knowledge and expertise and, in the process, enlarging it. In the words of a fellow Irishman also well known for is existential reckoning, 'Ever tried. Ever failed. No Matter. Try again. Fail again. Fail better'. ³

A triple aspect-the dialogue between effort, experimentation and experience; an historical, literary or contextual reference; and a personal connection that often provides a proxy for others to encounter matter in the throes of transformation-is typical of McPeake's work. Nowhere is this more obvious than in his singing bowls. They sound when struck, their vibrations stretching out in time and space as the mallet rubs their lips after an initial hit. In Asian cultures, including Laos and Myanmar where McPeake has worked extensively, bowls like these are carried by monks and nuns seeking food, money or other donations. In the context of contemporary Britain, it's tempting to read McPeake's versions as symbolic of widespread precarity, especially in the arts, with artists increasingly beholden to secure private support as cuts in public funding evidence austerity measures writ large. But within the body of work produced during the residency, McPeake's singing bowls resonate with more immediate and personal significance: as both vessels and disseminators of knowledge acquired through his learning episodes. Each bowl, cast from bell bronze, is distinct, its tonal qualities differing despite appearing similar to others in the series. When played individually, the bowls are greedy for our auditory, visual and haptic attention (it's all about me). But when played together, they refuse to collapse into a single, centrifugal sound (there is only we). And even when two bowls are struck simultaneously, it's never a faceoff (us/them) because other sounds also jockey for our attention: a dog barks in the night, a plane flies overhead, a cell phone rings...

The model of 'making sense' embodied in McPeake's singing bowls points to the human need not only for deep and diverse types of encounter but also for the time/space to dwell in their significance. McPeake's residency followed a similar logic. Like the bowls, his learning reverberates long after it can be perceived, with his experiments in unlearning also affirming for the artist what he well and truly knows.

So when it comes to the question posed above, 'How to make sense of our lives?' McPeake seems to suggest the answer resides with recalibrating our expectations. His artworks and practice challenge the clichéd aspiration of 'a life well lived' and prioritise instead something much tougher-harder to achieve but also more useful: a commitment to process, life as a process through which we're transformed in unexpected ways, some we have control over but others we don't. When it comes to making sense of our lives, we could do worse than to focus on sensuous experience, whilst accepting that its significance may only take its course as we're faced with heretofore unimaginable challenges and opportunities.
1 Adam Reynolds Memorial Bursary, Shape Arts, shapearts.org.uk (accessed February 10, 2015).2 Aaron McPeake, 'Nibbling at Clouds - The Visual Artist Encounters Aventitious Blindness' (PhD thesis, Chelsea College of Arts, University of the Arts London, 2013) available from ualresearchonline.arts.ac.uk/5871/ accessed February 10, 2015 3 Samuel Beckett, Worstward Ho, (London: John Calder, 1983), 7.

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Making Sensuous Knowledge: The Practice of Aaron McPeake Marsha Bradfield How to make sense of our lives? If you're inclined to take this as a moral question, don't. It doesn't ask how we should or ought to live. It wonders how we understand our experience of being.

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History Shorts: A Trailblazing Soldier Helps Build A National Park

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Colonel Charles Young overcame racism to rise through the ranks and create his legacy in the great outdoors.

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Who Was Carter G. Woodson?

Carter G. Woodson was the second African American to receive a doctorate from Harvard, after W.E.B. Du Bois. Known as the "Father of Black History," Woodson dedicated his career to the field of African American history and lobbied extensively to establish Black History Month as a nationwide institution. He also wrote many historical works, including the 1933 book The Mis-Education of the Negro. He died in Washington, D.C., in 1950.

Early Life

Carter Godwin Woodson was born on December 19, 1875, in New Canton, Virginia, to Anna Eliza Riddle Woodson and James Woodson. The fourth of seven children, young Woodson worked as a sharecropper and a miner to help his family. He began high school in his late teens and proved to be an excellent student, completing a four-year course of study in less than two years.

Higher Education and Harvard History

After attending Berea College in Kentucky, Woodson worked for the U.S. government as an education superintendent in the Philippines. He undertook more travels before returning stateside to continue his studies, earning his bachelor's and master's degrees from the University of Chicago.

Woodson went on to receive a doctorate from Harvard University in 1912, becoming just the second African American to earn a Ph.D. from the prestigious institution, after Du Bois. After finishing his education, Woodson dedicated himself to the field of African American history.

Associations and Publications

In 1915, Woodson helped found the Association for the Study of Negro Life and History (later named the Association for the Study of African American Life and History), which had the goal of placing African American historical contributions front and center.

Woodson established the scholarly publication Journal of Negro History in 1916, and to help teachers with African American studies, he created the Negro History Bulletin in 1937. Woodson also formed the African American-owned Associated Publishers Press in 1921.

Outside of his writing pursuits, Woodson held down several positions in academia. He served as principal of the Armstrong Manual Training School in Washington, D.C., before becoming a dean at Howard University and the West Virginia Collegiate Institute.

'Mis-Education of the Negro' and Other Books

Woodson wrote more than a dozen books over the course of his career, most notably Mis-Education of the Negro (1933). With its focus on the Western indoctrination system and African American self-empowerment, Mis-Education has become required reading at numerous colleges and universities.

Additional books from the author include A Century of Negro Migration (1918), The History of the Negro Church (1921) and The Negro in Our History (1922). Woodson also penned literature for elementary and secondary school students.

Creating Black History Month

Woodson lobbied schools and organizations to participate in a special program to encourage the study of African American history, which began in February 1926 with Negro History Week. The program was later expanded and renamed Black History Month. (Woodson had chosen February for the initial weeklong celebration to honor the birth months of abolitionist Frederick Douglass and President Abraham Lincoln.)

Death and Legacy

Woodson died on April 3, 1950, a respected and honored figure who received accolades for his vision. His legacy continues on, with Black History Month being a national cultural force recognized by a variety of media formats, organizations and educational institutions.

Woodson's accomplishments are also remembered through the University of Virginia's Carter G. Woodson Institute for African American and African Studies, and the Dr. Carter G. Woodson African American Museum in St. Petersburg, Florida.

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Carter G. Woodson was the second African American to receive a doctorate from Harvard, after W.E.B. Du Bois. Known as the "Father of Black History," Woodson dedicated his career to the field of African American history and lobbied extensively to establish Black History Month as a nationwide institution.

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Dying On Our Doorstep - How Britain Is Failing The Disabled
A Freelance article from Gemma Hurst
In an ideal world, everyone in Britain would experience life from a level playing field, all having the same opportunities, and able to proceed through life according to their skills, abilities, and wherewithal rather than according to the circumstance of their birth or physicality. Unfortunately, this is not the case. We all experience different levels of opportunity. Furthermore, we all have different limitations, and even different upbringings and cultural outlooks which affect the opportunities we are offered. Much of this differentiation is what makes British society the vibrant, interesting mix that it is - life would, after all, be very boring if we were all exactly the same. However, some certainly have a lot more opportunity than others - and the Coalition's policies appear designed to improve opportunity for the haves and to seriously reduce it for the have-nots. One of the groups being seriously affected by such policies are the disabled.
Taking From The Disabled To Give To The Rich
Those with a disability may have an awful lot to offer society. Most disabled people are capable of giving a lot, and certainly deserve the chance to live a normal, human lifestyle like everyone else. However, they may also need a degree of help to achieve this. Usually through no fault of their own, they may require a certain amount of support, perhaps in the form of care, perhaps in the form of specialist equipment. They may also be unable to work in the same manner as more conventionally able individuals. Thus their opportunities are already limited. Rather than consigning such individuals to the scrapheap, a just and moral society would seek to level the playing field by providing a degree of financial assistance to such people through benefits, thus allowing them the opportunity to achieve their full potential - or at least to live as full a life as they can. The Coalition appears to disagree. The less able seem, to them, nothing more than an inconvenience to whom as little aid as possible should be afforded. Consequently they have spent their tenure slashing benefits to the disabled and making it harder to claim disability benefit - all while affording various financial sops and tax breaks to the super-rich who have never wanted for anything. The money to cover these latter, incidentally, comes from slashed welfare and spending on public amenities like town halls, policing, and healthcare - all of which the disabled rely upon. Indeed, a Tory minister was overheard earlier this year mulling over the question of whether big business could save money by paying disabled employees less - earning a measly £2 an hour - as they are "not worth" [1] any more.
Disabled People Starving To Death
All of this is having a knock-on effect. Driven to the margins of society, the disabled are suffering even more than usual. In February of this year, a disabled man starved to death in Oxfordshire after benefit cuts left him with on £40 a week. He had been assessed by Atos Healthcare (under pressure from the government to cut disability benefits) as 'fit for work', yet, as the Oxford Mailreports, the inquest into his death found that he was "far from fit to hold down a job" [2]. Nor is this an isolated case. The Department for Work and Pensions has carried out sixty investigations into deaths as a direct result of disability benefit cuts since 2012 - and these are only the ones that have reached the attention of the government. Many more people are struggling, suffering, and dying quietly, without anybody taking any notice. It gets worse, though. According to the Guardian, hate crimes against the disabled are at the "highest level since records began" [3]. Most commentators are in little to no doubt [4] that the cause of this is the 'anti- scrounger' rhetoric and propaganda both spouted and encouraged by the Coalition.
Exclusion From Opportunity
Many with disabilities are increasingly being excluded from many areas of our society by the removal of basic opportunities. For example, funding for disabled students has been cut for many universities, hitting their ability to cater to the needs of disabled students hard. Furthermore, many grants and allowances for disabled students are steadily being withdrawn. Disabled students may be unable to undertake the kind of jobs that more conventional students would do in order to earn money, and may also require specialist equipment in order to complete their studies - thus putting their expenses up while simultaneously eliminating their ability to earn those expenses.

While certain grants and funds are available for those who need them, they're becoming fewer, and those which remain are getting harder and harder to access. Indeed, Disabled Students Allowances - the biggest and most reliable (which isn't saying much) - source of disabled student funding is to be cut from 2015. The knock-on effect of all this will naturally be that bright, intellectual, but disabled students will struggle to fund their studies in the same way that their classmates can, and all but those disabled young people with super-rich parents will therefore be excluded from the opportunities offered by higher education.
A Morally Bankrupt Society
Disabled people do not choose their disability. It comes upon them as an accident of birth, of genetics and fate. It is no fault of their own, and punishing them for such an accident is heinous and wrong. While there will always be unscrupulous people who try to exploit the system, the number of taxpayers' money lost through benefit fraud absolutely pales into insignificance when compared to the amount of money lost through tax evasion by corporations and the ultra-rich (whom the Coalition, incidentally, appear to have no intention whatsoever of 'cracking down' upon). It is certainly not worth cutting everyone's benefits in order to winkle out the very few who are abusing the system. At the moment, this benefit-slashing and 'scrounger' rhetoric is hurting the most vulnerable people in our society - and, as Ghandi said, a society is measured by how it treats its weakest members. British society under the Coalition is scoring very low indeed on the Ghandi scale.

[1] Adam Withnall, "Lord Freud disabled wage comments: 'Those words will haunt him', says Tory

MPs as peer faces calls to resign", The Independent, October 2014

[2] Katriona Ormiston, "Man starved after benefits were cut", Oxford Mail, February 2014

[3] The Guardian, "Disability hate crime is at its highest level since records began "

[4] Ben Riley-Smith, "Hate crimes against disabled people soar to record level", The Independent,

June 2012

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Dying On Our Doorstep - How Britain Is Failing The Disabled

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In an ideal world, everyone in Britain would experience life from a level playing field, all having the same opportunities, and able to proceed through life according to their skills, abilities, an...

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路易·布莱叶 - 维基百科，自由的百科全书

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路易·布莱叶（法语：Louis Braille，发音：[lwi bʁɑj]，又译布拉耶，（1809年1月4日－1852年1月6日）是世界通用的盲人及视觉障碍者使用的文字系统布莱叶点字法的发明者。布莱叶点字法是一种通过阅读者用手指触摸由突起的点组成的文字进行阅读的方法。这种系统已经适用于几乎所有的已知语言。

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Description

Visually impaired people have to constantly adapt to a world that wasn't built for them. To help them live a better life, we created an AI-powered white that builds a 3D soundscape so they can "see" and navigate the world easily and safely. To promote this white cane, we'll place both Braille and audio-based ads explaining the cane's functionality in key places visually impaired people already have to go through while walking as crosswalk buttons and bus shelters. Visual ads will also be placed around the city so everyone else helps spread the word about the product.

This student campaign titled 'Blindless' was published in Spain in December, 2018. It was created for the brand: Google, by ad school: Miami Ad School. This Integrated medium campaign is related to the Electronics, Technology industry and contains 3 media assets. It was submitted almost 3 years ago by Art Director: Andrea Serrano Villaverde.

Credits

Advertising School: Miami Ad School
Ad: Andrea Serrano Villaverde
Copy: Andrea Serrano Villaverde
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Google: Blindless * Ads of the World™ | Part of The Clio Network

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Visually impaired people have to constantly adapt to a world that wasn't built for them. To help them live a better life, we created an AI-powered white that builds a 3D soundscape so they can "see" and navigate the world easily and safely.

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Accessibility for Everyone

Today's web must be made accessible for everyone-regardless of a person's abilities or impairments.

"Accessibility ensures people with disabilities can access the same information from a system as everyone else, and also gain the same benefits"

As outlined in a previous article, there exists a wide range of impairments, from five notable areas:

This guide will focus on designing for visual impairments, which can be quite common, ranging from mild to extreme disabilities. In fact, Cathy O'Conner (designer, and author for Smashing Magazine) estimated that for every two million online customers, around 200,000 would benefit from designs that are easier to see.

That's a fair estimation, especially considering how anyone can develop low vision impairments as they get older.

Types of Visual Impairment

Common visual impairments can include:

Color Blindness

Color Blindness involves difficulty in perceiving or distinguishing between colours, as well as sensitivity to color brightness. It affects approximately 4.5% of the entire global population.

Low Vision

Low vision can include partial sight in one or both eyes, poor acuity (blurry vision), tunnel vision, central field loss, and clouded vision. It affects 246 million people, or about 4% of the world's population.

Blindness

Blindness is the substantial loss of vision in both a person's eyes. It affects approximately 39 million people, or 0.6% of people.

People Perceive the Web Differently

The diverse nature of these impairments can create a wide variation in how web pages are perceived by people with different visual abilities. As outlined above, a large number of people suffer from visual impairments, so we must ensure they can access and interpret all features the same.

Viewing the Tumblr Homepage With Visual Impairments

As an example, consider Tumblr's homepage, where the background of the page is set to a large image (created by their users):

Depending on the type and level of visual impairment a person may have, the site could be perceived in a number of ways (here simulated with the NoCoffee Chrome extension):

The examples above show different types of low vision impairments, and also a couple of examples of colour blindness. To summarise:

Tunnel vision (see image 1) is a type of blocked peripheral vision, which reduces the amount of visible elements on the screen. The user can only see central elements.

Loss of acuity, or blurred vision (see image 3), makes text difficult to read, as it becomes fuzzy to the user.

Color blindness (see image 5) reduces the number of colours a user can see, so there is more chance that elements can appear to be similar.

Variations in Perception Affect Usability

Due to these variations in perception, key elements of a given website can become less accessible (and therefore less usable) depending on the extent of a user's visual impairment.

Inaccessible features

For example, a loss of acuity (blurry vision) can make the search bar on the Tumblr website almost disappear into the background. The same can be said for the login button:

Compare the search bar on the image to the left with that on the right-on the right, the search bar has blended into the background, and is barely visible.

Colors lose significance

Moving away from the Tumblr example, consider a person with red/green color blindness (protanopia). On a Google search results page, the color used to represent the current page of results appears less significant to a color blind user, possible making it slightly less meaningful:

The contrast from red and yellow, is less obvious to a color blind user, and appears more like a light greenish color against a dark green.

Presentation of Content

Both of the above examples show how variations in perception can affect the usability of core features. Thankfully though, people with such visual impairments can alter the presentation of content so that elements become more accessible and usable to them. This can be done by:

🔍 Enlarging the text size

🎨 Customizing color contrasts

👁‍🗨 Using screen readers (blindness)

🎞 Subtitles or captions on videos

📝 Alternative image text to describe images

Such adjustments can be made through default settings in a web browser. Additionally, more advanced alterations have been made available through browser accessibility extensions. For example, Google have built various accessibility plugins for visually impaired users:

ExtensionAccessibility Developer Tools: add an Accessibility audit, and an Accessibility sidebar pane in the Elements tab, to your Chrome Developer Tools.

High Contrast: browse the web with your choice of several high-contrast color filters designed to make it easier to read text.

ChromeVox: brings the speed, versatility, and security of Chrome to visually impaired users.

High Contrast, for example, lets people vary the contrast of a website, making text clearer to read. Here it is in action on the Spotify homepage:

As seen above, the browser extension can:

Increase contrast

Set to grayscale

Invert colors

Invert grayscale

Use yellow on black

With all the different visual impairments, and the large range of tools that can be used to alter how content appears, it becomes clear that we cannot always determine how web pages will be displayed or perceived by people.

Since content can appear in a number of ways, we must therefore be careful of how our content is structured, even at the coding level. That's because it becomes important to maintain a clear hierarchy of information, as people can use different means to present that information. Let's now take a look at some best practices to ensure our content is always accessible, no matter how it is displayed:

Best Practices

Here's a list of six best practices to make your designs better for those with visual impairments.

1. Separate Content and Structure

It's important we ensure web content is independent of its underlying structure. When changes to presentation can include the size of elements (such as text and images), the spacing between elements, or whether elements can be seen at all (blind users may not see images), it becomes clear that the developer can't determine how content will be viewed at any given time.

As stated by the W3C, to enable different browsing methods to work (e.g. using screen readers or keyboard navigation), developers must ensure that their code provides a structure that is independent of presentation:

"Developers need to ensure that the presentation of web content is independent of its underlying structure" - W3C

A solid structure will also provide relevant semantic tags such as headers, paragraphs, and list item tags to ensure that, for example, a screen-reader can interpret the information and present it in an alternative way:

2. Provide Text Alternatives

As explained previously, certain structural elements, especially images, cannot be perceived by some users. For instance, blind people using assistive technologies (such as screen readers) to interpret websites will hear the alternative text attributed to the image read out, rather than actually seeing the image. If that text is not present, or fails to be descriptive enough, they won't be able to perceive the information as intended.

Here is an example from the University of Leicester, showing accurate alternative text, which provides more context to the user:

Ability.net provide five golden rules for using alt tags (text alternatives) correctly in order to make a website more accessible:

1. Every <img> must have an alt="" attribute

2. Describe the information, not the picture

3. Active images require descriptive alt text

4. Images that contain information require descriptive alt text

5. Decorative images should have empty alt text

3. Avoid Using Color to Convey Information

Color is not the best way to convey information, as shown by the following example. Below, a red border is used to highlight form fields that have not been filled in correctly. Consequently, if a user is color blind, they won't be able to see this indication, so it becomes difficult to understand which fields have errors:

The use of icons and labels to show which fields are invalid better communicates the information to a color blind user:

Example from Bootstrap v4

This example shows that color should not be used on its own to convey information, but only in addition to existing information.

4. Use Textures Instead of Color

Color blind users may also find it difficult to tell the difference between certain colors. For instance, green, red, and brown can look very similar:

Therefore, when colors are used on charts and graphs, it can be useful to apply patterned overlays to solid colors in order to give users a clearer way to distinguish between elements. This not only helps those who are color blind, but also makes it easier for everyone. Consider Trello's labels for an example of applying textures:

5. Try Monochromatic Color Schemes

Monochromatic color schemes make use of only the colors of a single hue. Here's an example, created with paletton.com:

By only using shades of a single hue, any extra meaning that would could have been introduced by different color hues are removed.

Variations in contrast and tones can be used to provide meaning or importance to elements, and attract user attention to different areas. The meaning here can also be more easily carried across to color blind users as shown in the following example of a monochromatic site.

BIGSOUND Buzz is a website that makes great use of a monochromatic color scheme:

A colour blind user will see all the same tones and contrasts, but in a different hue:

6. Use Contrasting Colours for Better Readability

Contrast is the difference between the lightest color (e.g. the background), and the darkest color (e.g. the text). For example, consider this contrast sensitivity chart:

The top left (letter A) has the highest contrast, and as we move right, the contrast decreases, as the difference in luminance between background and foreground reduces. Eventually, depending on a person's contrast sensitivity, they won't be able to distinguish the text from the background.

Therefore, to ensure text is readable by people with visual impairments, the WCAG has provided a contrast ratio guideline. They suggest that a contrast ratio of at least 4.5:1 should exist between a text and its background. This ratio drops to 3:1 for larger text (24px or 29px bold).

An example of this ratio is shown in the examples below, from accessebility.psu.edu:

Inclusive Design Improves the Product for Everyone

Overall, by designing inclusively of the most extreme disabilities first, it almost always improves the end product for everyone else.

For instance, designing for people with no vision can lay a great foundation for those who can see. This is because it puts us in a position to ensure that the structure of the website is independent of its presentation, and can be interpreted by assistive technologies as well as people. Therefore, if presentational changes were to happen for any other reason, the structure of the website will still be accessible.

Additionally, ensuring color is only used to highlight what is already visible is another great step towards building a highly accessible, and therefore usable website. A useful design process can therefore be to design early iterations of a product in grayscale, and then apply colors at the very end.

Further Reading and Resources

You don't need to reinvent the wheel when creating accessible designs; there are many design systems and guidelines that can help you.

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Accessibility Basics: Designing for Visual Impairment | Envato Tuts+

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This guide will look at how designing for people with visual impairments can improve the web for everyone.

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Karwai Pun is an interaction designer currently working on Service Optimisation to make existing and new services better for our users. Karwai is part of an accessibility group at Home Office Digital, leading on autism. Together with the team, she's created these dos and don'ts posters as a way of approaching accessibility from a design perspective.

The posters

The dos and don'ts of designing for accessibility are general guidelines, best design practices for making services accessible in government. Currently, there are six different posters in the series that cater to users from these areas: low vision, D/deaf and hard of hearing, dyslexia, motor disabilities, users on the autistic spectrum and users of screen readers.

The dos, that run across various posters, include using things like good colour contrasts, legible font sizes and linear layouts. So, aren't good design principles applicable to everyone and not just those with access needs?

While this is true, the aim of the posters is to raise awareness of various conditions through good design practice. We need to be mindful of not just designing or building for our own immediate needs. For example, consider designing for keyboard use only. This is particularly helpful for users with motor disabilities where using the mouse can be quite difficult, especially with precise movements, whereas keyboard use is much easier.

Another aim of the posters is that they're meant to be general guidance as opposed to being overly prescriptive. Using bright contrast was advised for some (such as those with low vision) although some users on the autistic spectrum would prefer differently. Where advice seems contradictory, it's always worth testing your designs with users to find the right balance, making compromises that best suit the users' needs.

The team

The content for the posters came from our accessibility team in Home Office Digital. Led by accessibility leads Emily Ball and James Buller, we are a group of twelve, each specialising on these conditions: blind and visual impairment, dyslexia, autism and ADHD, D/deaf and hard of hearing, mental health and motor disabilities. Collectively, we learn as much of the conditions as we can to better increase our knowledge so they can be shared within and outside the team.

One of the challenges we faced with the posters was gathering information from our different specialisms and reducing the vast amount of knowledge to ten principal dos and dont's. There's also challenges surrounding content and graphics. I worked with Nick Cowan, a content designer, who is leading on motor disabilities, to keep the content concise and ensure the graphics visibly represented the advice accurately.

Next steps

We've shared these posters across government for feedback and they can be found on GitHub.

We are constantly improving and adding to them so please let us know what you think. Understanding accessibility through design means we can build better services for everyone, whatever their access need.

Update: We've been asked whether these posters can be reproduced or translated into other languages. In keeping with the the GDS ethos of making things open, we've used a Creative Commons license which allows everyone to share, use and build upon the posters provided they are used non-commercially and keep the appropriate attributions (Home Office, Home Office Digital and the Creative Commons logo). It would be great if people can share photos of them being used on Twitter and can commit translations of the posters to our GitHub repository so they're available for everyone.

What the posters say

Designing for users on the autistic spectrum

Do

Don't
View poster for the autistic spectrum
Designing for users of screen readers

Do

Don't
View poster for screen readers
Designing for users with low vision

Do

Don't
View poster for low vision
Designing for users with physical or motor disabilities

Do

Don't
View poster for physical or motor disabilities
Designing for users who are D/deaf or hard of hearing

Do

Don't
View poster for Deaf or hard of hearing
Designing for users with dyslexia

Do

Don't
View poster for dyslexia
Follow Karwai on Twitter and don't forget to sign up to email alerts.

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Dos and don'ts on designing for accessibility

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Karwai Pun is an interaction designer currently working on Service Optimisation to make existing and new services better for our users. Karwai is part of an accessibility group at Home Office Digital, leading on autism. Together with the team, she's created these ...

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Use a font with a high colour contrast and a readable font size

Don't use low colour contrasts and small font sizes

Making the default appearance of text easy to read will mean that people with visual impairments can take in the information (quicker), particularly if assistive technology is not available.

Publish all information on web pages

Don't bury information in downloads

HTML is the most accessible format because users can change the appearance of web pages to meet their needs - for example using high contrast colours or large fonts. The text can also be read aloud. Other formats often require extra steps and software to open, and can be harder to navigate and have less flexible display options.

Use a combination of colour, shapes and text

Don't only use colour to convey meaning

Colour vision deficiency (colour blindness) is a common condition which makes it difficult to identify certain colours. This can make it hard to understand elements like buttons and graphs which rely only on colour to convey information. Use other signifiers like text labels or different styles of dashed lines in those cases.

Follow a linear, logical layout

Don't spread content all over a page

Users of screen magnifiers can miss content like side columns if they are not expected or well sign posted. Particularly if they use the tab key to move between links and form elements. Place features in a logical order where users would expect them to be.

Some users choose to enlarge text as well as or instead of using magnification features. The design should flex accordingly, showing a mobile, single column layout.

Put buttons and notifications in context

Don't separate actions from their context

When using a screen magnifier, it is disorientating for a user to hunt around the page for an element. Put things like help text, error messages, submit buttons and notifications close to the thing they relate to.

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Home Office Digital, Data and Technology

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Making the default appearance of text easy to read will mean that people with visual impairments can take in the information (quicker), particularly if assistive technology is not available. HTML is the most accessible format because users can change the appearance of web pages to meet their needs - for example using high contrast colours or large fonts.

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The black dots in the fluid layer flow as they move, simulating the characteristics of floating spots

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use epoxy

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The silicone is too soft to keep the shape of the pages, and the colors are not clear enough to see the pattern underneath, and it is not strong enough to wrap the fluid layer in the middle, causing the glycerine to flow out

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Add the glycerine to create the fluid layer

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Add the glycerine to create the fluid layer

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cut them to represent the symptom of Floating spots

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cut them to represent the symptom of Floating spots

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paint black spots

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This is a book made to make normal people more aware of people with diabetic retinopathy.
The book presents a first-hand view of what I would see on my way to school if I were a person with diabetic retinopathy, using familiar scenarios to simulate the different symptoms with different materials or techniques, so that the public can understand the dangers of the disease and feel the pain experienced by these patients. The aim is to make some urban construction workers take the needs of the visually impaired more into account in their subsequent work.

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The world of the blind, as it were, lacks a 'language' of communication, and those of us watching the video can only guess the scene they are in by the sound and the blurred shadows. For this project, I wanted to experience the world of the blind by touching their surroundings with my eyes closed and listening to the sounds and finally using my sense of touch to recreate the scene. The viewers of my work will be able to guess where I might be through sight, touch, smell, and hearing. It is a two-way interaction.

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Aaron McPeake regularly uses the shadow as a simile for what he sees. In this film, he attempts to re-enact the journeys of the 19th-century blind explorer James Holman.
Filming in countries such as Thailand, Cambodia and Laos, McPeake limits the visual documentation of his travel experiences to monochrome shadows and ambient sound, and invites the viewer to work hard to interpret what they are seeing and hearing. McPeake also references the tradition of kulit or shadow theatre, widespread throughout Asia, as a means of voicing the story of a blind traveller, a story that might not otherwise be told.

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using epoxy and materials to create the feeling that day I felt

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using epoxy and materials to create the feeling that day I felt

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pretend I am blind, to feeling the environment around me

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pretend I am blind, to feeling the environment around me

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add

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Ancient Egyptians gave us the key to reach enlightenment

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Ancient Origins Reconstructing the story of humanity's past

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The Eye of Horus is one of the best-known symbols of ancient Egypt. Known also as the Wadjet, this magical symbol is believed to provide protection, health, and rejuvenation. Due to its powerful protective powers, the Eye of Horus was popularly used by the ancient Egyptians, both the living and the dead, as amulets. Even today, the Eye of Horus continues to be used as a symbol of protection.

The Dramatic Origin - A Story of Betrayal and Murder

The origin of the Eye of Horus may be found in the myth of Set and Osiris. The ancient Egyptians believed that Osiris was the king of Egypt and that his brother, Set, desired his throne. Through trickery, Set succeeded in murdering his brother and became the new king. Osiris' wife Isis, however, managed to bring her husband back to life temporarily through magic and became pregnant with Horus.
A rare sample of Egyptian terra cotta sculpture depicts Isis mourning Osiris. The sculpture portrays a woman raising her right arm over her head, a typical gesture of mourning. (Louvre Museum / Public Domain )
The Cost of Vengeance and the Gift of Restoration

Osiris went on to become the god of the Underworld and Isis raised Horus on her own. When Horus reached adulthood, he sought to avenge the death of his father. Horus fought Set in a series of battles, and eventually vanquished his uncle. During these struggles, however, he lost one of his eyes. According to one version of the myth, Set had ripped out Horus' eye, tore it up into six parts and threw it away. In another version, it was Horus himself who gouged his eye out, as a sacrifice to bring his father back from the dead. In any case, Horus' lost eye was magically restored by either by Hathor (often regarded to be the consort of Horus), or by Thoth, the god of wisdom.

As Horus' eye was magically restored, the ancient Egyptians believed that it possessed healing properties. Amulets of this symbol have been made using a variety of materials, including gold, lapis lazuli, and carnelian, and have been used as jewelry by both the living and the dead.
An ancient carving of the Eye of Horus ( Travis / Adobe Stock )
Is the Eye of Horus a Magical Mathematical Symbol?

In ancient Egyptian hieroglyphic orthography, isolated parts of the "Eye of Horus" symbol were believed to be used to write various fractions. (BenduKiwi / CC BY-SA 2.5 )
Interestingly, the Eye of Horus is not merely a magical symbol but is also an example of the mathematical knowledge acquired by the ancient Egyptians. In the myth mentioned before, Set tore Horus' eye into six parts. As a symbol, the Eye of Horus contains six parts. Each of them was given a fraction as a unit of measurement - the right side of the eye is 1/2, the pupil 1/4, the eyebrow 1/8, the left side of the eye 1/16, the curved tail 1/32, and the teardrop 1/64. These fractions add up to 63/64, and the missing part is said to either represent the magical powers of Thoth or to illustrate that nothing is perfect.

The Distinctive Meanings of the Parts of The Eye of Horus
Two Eyes of Horus can be seen at the front of this traditional Luzzu boat at Marsaxlokk harbor in Malta ( Anibal Trejo / Adobe Stock Top image: An Eye of Horus pendant. Photo source: (Jon Bodsworth / Wikimedia) ).
Each of the six parts of the Eye of Horus correspond to a different sense. The right side of the eye is associated with the sense of smell, as it is closest to the nose and resembles this organ. Needless to say, the pupil represents the sense of sight, while the eyebrow represents thought, as it can be used to express our thoughts. The left side of the eye represents the sense of hearing, as it points towards the ear, and has the shape of a musical instrument. The curved tail resembles a sprout from a planted stalk of wheat or grain. As a representation of food, this part of the Eye of Horus corresponds to the sense of taste. Finally, the teardrop is supposed to represent the sense of touch, as this part of the Eye represents a stalk being planted into the ground, an act that involves physical contact and touching.

How is The Eye of Horus Used Today?

Although the ancient Egyptian civilization came to an end, the belief in the potency of the Eye of Horus continued and this symbol is still used by many today. As an example, in Mediterranean countries, fishermen would often paint this symbol on their vessels for protection. Additionally, many people still wear the Eye of Horus as jewelery, to protect themselves from the ill-will of others. Moreover, the Eye of Horus is popular amongst occultists, as well as conspiracy theorists, who view the Eye not only as a protective symbol, but also as one of power, knowledge, and illusion.

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Eye of Horus: The True Meaning of an Ancient, Powerful Symbol

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The Eye of Horus is one of the best-known symbols of ancient Egypt. Known also as the Wadjet, this magical symbol is believed to provide protection, health, and rejuvenation. Due to its powerful protective powers, the Eye of Horus was popularly used by the ancient Egyptians, both the living and the dead, as amulets.

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In Egypt, the Eye of Horus, also known as a wedjat, is believed to bring good luck. Legends tell that the god Horus battled the god Set to reclaim the throne of Egypt. In the fight, Set plucked out Horus' left eye while he slept, then broke it into six pieces and scattered them. The god Thoth embarked on finding the pieces, to reconstruct the eye. Finding only five pieces, he replaced the missing fragment with one that had divine qualities, allowing Horus to see beyond the visible.
Eyes are described as windows to the soul, but offer insight into our health.
The eye of Horus represents the hope of health therefore in visually impaired's heat should have an Eye of Horus, they use different ways to 'see' the world.