Visual Disabilities

Table of Contents

  1. Demographics
  2. Medical Details
  3. Accommodation

Demographics

2.2 billion people have vision impairment, of which 1 billion have a vision impairment that either could have been prevented, or has yet to be addressed.

Most people with a form of vision impairment are over the age of 50.

1 in 12 people assigned male at birth have red-green colour vision deficiency, as opposed to 1 in 200 people assigned female at birth (among people with Northern European ancestry).

1 in 10 000 people have blue-yellow colour vision deficiency.

246 million people (3.5% of the population) have low vision, and 90% of which live in low income settings.

Medical Details

There are many, many conditions that can cause a wide range of vision problems. Although it is not explicitly linked to, I'd encourage anyone to read the American Foundation for the Blind's Glossary of Eye Conditions because it can give a sense of the sheer range of variation.

The Body of Knowledge charts out visual disabilities as disabilities that include any or some of the following: loss of vision to different degrees, loss of sharpness/visual acuity, loss of sensitivity to colours. But read through the Glossary, and you will find so many other different manifestations. For the purposes of the exam, we're going to look at three kinds of profiles: colour vision deficiency, low vision, and Blindness.

Low Vision

While there are technically very specific numbers and measures that define what is and isn't 'low vision' in (for example) legal contexts, the AFB alongside a selection of practitioners prefer a functional definition. In Low Vision and Legal Blindness Terms and Descriptions, a linked BoK source, the AFB defines low vision as basically being "not enough vision to do whatever it is you need to do" which can truly vary from person to person.

People with low vision can use technology intended for low vision people like magnification.

Low vision can range "from moderate impairment to near-total blindness," as defined by the Glossary I linked to earlier.

Blindness

Many Blind people retain some degree of light perception, or the ability to see vague shapes. Some Blind people have total vision loss which is known as 'NLP' or 'no light perception.'

Blindness is a spectrum and can range from some vision loss, nearly complete vision loss, and complete vision loss.

Clarifying Low Vision vs Blindness

Astute readers will have already picked up on something fishy going on here. Low vision is a spectrum, from moderate impairment to near total blindness. Blindness is a spectrum, ranging from some to total vision loss. How the heck are these two things different?

The most obvious difference is that people with total vision loss will definitely not be using the term, 'low vision.' For people with some vision and/or light perception, the question is a bit more nuanced. While the general trend is that people with more functional vision will tend towards identifying with the 'low vision' label and people with less functional vision will tend towards identifying with the 'Blind' label, we should take some time to describe the different aspects of these words that might influence an individual person's identification.

Low vision and blindness have strict definitions when used in medical and demographic contexts. There is a number cut off between low vision and what is commonly called 'legal blindness,' but I feel 'medical blindness' might be more appropriate, as it is defined in the International Classification of Diseases, 11th edition. For example, the WHO used ICD-11's number cut off when they were determining how many low vision people there are globally. Here's an excerpt from their 2012 announcement.

WHO estimates that the number of people with visual impairment (presenting vision) is 285 million (65% of whom are aged over 50 years). Of these, 246 million have low vision (63% over 50) and 39 million are estimated to be blind (82% over 50).

In using the cut-off, there is absolutely no overlap between people defined as 'blind' and people defined as 'low vision.'

But the medical definition is not the only one used, nor is it the only definition used to assess 'legal blindness' across nation states of the world. Nations and jurisdictions also may have their own definitions of 'low vision' and 'blindness' to use in the field of education, as an indication of what kind of schooling has been determined to be most appropriate for the child.

The word, Blind, is also sometimes taken up as a marker of social identity. People who have low vision or medical blindness have historically had a very similar position in society. They share common experiences and barriers, and access resources from similar organizations such as the American Federation of the Blind and other members of the World Blind Union. Not as many laypeople are entirely familiar with words like 'low vision,' and so Blind as a term may come across as honest and accessible.

We can see this identity version of the word 'Blind' well at work in the case of the word, 'DeafBlind'. DeafBlind is a label taken up by people who have a wide range of functional vision and functional hearing. One never hears about a person who is Deaf-low-vision, or Hard-of-hearing-low-vision.

In this blog, I often use the word in the expanded social identity sense to refer to Blind people as it aligns with the general convention that this blog takes to the promotion of the identity model of disability. I hope this is obvious, but do respect the preferences people have with what they would like to be called. Some people out there fully prefer the term 'visually impaired' as opposed to 'blind,' perhaps feeling like the word carries a negative connotation or stigma. Others feel the opposite. Some people with a small bit of functional vision will gravitate towards the 'low vision' label, others will feel that they are Blind.

To summarize, low vision and blindness have strict medical definitions. Used non-medically, both words are recognized as being applicable to people who still retain various degrees of light perception and vision. The decision to embrace one label or the other is largely cultural and ultimately comes down to personal preference.

Colour Vision Deficiency

According to Medline Plus, a linked BoK source, colour vision deficiency is commonly referred to as colour-blindness.

The most common type is red-green, where shades of red, yellow, and green, may be difficult to distinguish from one another.

Blue-yellow or tritan defects make it hard to distinguish blues from greens, and dark blues from black. This condition is rare.

Blue cone monochromacy features severely reduced color vision, alongside a slew of other symptoms including loss of sharpness, sensitivity to light, nearsightedness, and involuntary eye movements.

Achromatopsia and blue cone monochromacy may be considered to be variations of the same condition. Achromatopsia is more severe, having similar vision symptoms but sometimes resulting in total lack of color vision.

Colour vision deficiency is most often a condition experienced from birth, where it is often hereditary. However, people also may gain colour vision deficiency later in life after some kind of injury: after retinal detachment, laser eye injuries, radiation treatment, and brain tumours affecting the optic nerve.

Accommodation

Colour Information

In accommodating people with colour vision deficiency, the most common advice is to simply not rely on colour to convey information. For example, error messages that rely on only a red outline is not an acceptable pattern, as it violates SC 1.4.1 Use of Color in the Web Content Accessibility Guidelines. Links that are only distinguished by colour also fail this guideline.

There are so many things that commonly use colour to provide information. Many pie charts and complex graphics rely on colour to distinguish between groups of data. Traffic lights. The use of red or green to indicate that something is finished charging, or a TV hub or home assistant that uses a green light to indicate it's been configured properly. The identical condiment containers, red and yellow, for ketchup and mustard. The colour of sports teams jerseys.

Some things naturally give information about themselves through colour. Ripe fruit, especially bananas and tomatoes. Is this steak meat rare or medium? Does my child have a sunburn?

Some people with colour vision deficiency wear special contrast-enhancing contact lenses or glasses. They might use colour-changing themes or high contrast mode when browsing the web. They may also rely on apps that can tell what colour things are from a picture.

Solutions that Fit the Situation: Low Vision Tech

There are a lot of assistive technology and accommodation strategies out there. The appropriateness of these situations is always going to be different from person to person.

There is a class of assistive technology often referred to as 'low vision assistive technology' that is meant to be used by those with some remaining vision left.

We're talking mostly about different kinds of magnifiers and zooming technology. They can be portable handhelds, such as a literal magnifying glass, to video magnifiers (or 'CCTV') that can project very large images onto walls, to screen magnification settings on phones or computers that can magnify and zoom to very high levels like 1500% (sometimes paired with large monitors), screen-magnification programs like ZoomText that provide contrast themes alongside magnification.

High contrast themes are another example of AT intended for the low vision population. Originally known as Windows High Contrast Mode, Windows has since migrated and renamed the feature, and different devices and platforms and extensions now supply their own version of this effect. Web designers can specify certain stylings to only appear when high contrast themes are active through the use of a @media query.

People with low vision also might prefer materials provided in large print. For example, large print phones and keyboards, large print calendars, large print keyboards.

Tech for No Vision

Accompanying this is a bunch of assistive technology and techniques that do not require any vision to operate. People with some vision left may also use this tech in conjunction with tech that does rely on some remaining vision.

Braille

Braille is a way to encrypt letters, numbers, sound abbreviations, and even full words, into six tactile dots arranged into a two-by-three vertically-oriented rectangle. Braille codes change depending on what language the text is written in. For example, Luxembourgish Braille actually relies on an eight-dot system, arranged in a two-by-four rectangle.

Children often pick up Braille faster than adults. The percentage of Blind and low vision people who are proficient in Braille is actually quite low. Learning Braille requires Blind people to have high sensitivity in their fingers, which not everyone has, and learning it as an adult requires some patience as the tactile sensitivity that is needed takes time to develop and acquire. Nowadays, when people lose their vision later in life, they might prefer using synthesized speech instead of endeavoring to learn a whole new system.

However, Braille remains essential to developing good literacy for Blind children and achieving equivalent academic outcomes. It's the only way for them to really learn the ins and outs of spelling and arithmetic, and as the amount of people who actively learn Braille is on the decline, Blind advocates continue to push for its promotion, especially to parents of Blind children who are making decisions about their child's education. DeafBlind people also rely on Braille to access text.

Braille might be written with a slate and stylus (kinda like the equivalent of Braille handwriting), with a mechanical Braille writer (kinda functions like a typewriter), and a Braille embosser (like an ink printer, but for Braille). Braille embossers and Braille writers are several thousands of dollars each. Even Braille labelers, that output small labels that can be used to label things like pantry items and skincare products, can literally cost more than a thousand dollars. There are cheaper ones available on Amazon for less than a hundred, though.

Refreshable Braille displays can be hooked up to a computer to display output from a screenreader. Following the trend, these too are very costly. Wait, what is a screenreader?

Screenreaders

Screenreaders software is not the same as text-to-speech software. A screenreader is a piece of software that converts computer interface and web content provided from browsers into a text-only interface. Output from screenreader software can either be voiced through synthetic speech (text to speech), or sent to a refreshable Braille display. A person using a screenreader will generally use the keyboard, instead of a computer mouse, to navigate. In doing so, they have access to a bunch of keyboard shortcuts that they can use to jump between components and sections of the interface or content.

Here are some questions or directions that can be quickly asked and answered through keyboard shortcuts:

Here are some popular screenreaders:

Browsers and screenreaders work very closely together. Browsers create a version of the content, referred to as the 'accessibility tree' that the screenreader uses to generate output. Each screenreader has a browser that it works best on and each has their own little quirks and tricks. If you are working with screenreader testing, or would like to get a taste about considerations in UX for screenreader users, read Don't Override Screenreader Pronounciation by Adrian Roselli.

To work properly, websites need to be designed in ways that are screenreader-friendly. They need to be fully keyboard operable. They need to use proper semantic marking for interactive components. Graphics and media should have textual alternatives. There are lots of ways to fuck this up, and many screenreader users regularly struggle with accessing content on websites.

Household Tech

I already mentioned Braille labelmakers. There are various pieces of assistive tech that have been developed to address some unique challenges that one encounters as a Blind person going about life.

Voice note recorders and home assistant devices may also be used for everyday tasks.

Orientation and Mobility

Orientation and Mobility training is offered by many organizations and reinforces skills in navigating independently through new and old spaces. O&M trainers will typically perform an assessment on their trainee, taking into consideration their current navigation skills, functional limitations and goals. Some people, especially those who have lost their vision later in life, already know the layout of their neighbourhoods and points of interest, and just need help learning how to traverse safely. Other folks may be more interested in gaining more advanced navigation skills to navigate new environments independently with confidence.

The signature O&M tool is the cane, and it comes in three types. All three types are generically white with a red stripe near the bottom, serving as an identifier to other pedestrians that a person has some kind of visual disability. Unsightly Opinions's YouTube Short on cane types really helped me visualize the different kinds.

  1. Identification cane, or ID cane. Also sometimes called 'symbol canes.' Thin and straight, like a pool cue for billiards. It's used by people who don't need a full mobility cane, but still would like to let other people know that they have low vision. It's largely symbolic, held off the ground in front of the self, and can also be used for simple probing.
  2. Support cane. A version of identification cane that one can use to support their body weight, usually used by people who are physically disabled or older adults.
  3. Mobility Cane or 'long cane' is swept in front of the self to search for tactile feedback. They are much thicker and durable. They come in various materials, some heavier and some lighter, some more rugged, and others more chic. Some have a rolling ball at the end, some have a collapsible spring that prevents people from getting jabbed in the gut. The most common type of mobility cane folds down into about five or six sections, but others can collapse into itself like a telescope, and others don't fold down at all.

The other classic O&M tool is the guide dog. A guide dog is very good at avoiding obstacles, stopping for overhead obstacles, stopping for changes in elevation, and leading people using what's called the 'straight line principle.' Guide dogs are not meant to replace the need for an individual to build their own O&M skills. People who navigate with guide dogs usually first receive training to navigate with a mobility cane. Here are some resources if you'd like to learn more:

Guide dogs cannot set new routes. They aren't GPS. Audio-based navigation interfaces that use actual GPS can help people determine new routes. New routes may also be learned through tactile maps, or human navigators.

The Built Environment

O&M training and tools work best in accessible environments. These environments have tactile markers on the ground to indicate changes in elevation and the start of a crosswalk, audio or tactile interfaces and sound cues at pedestrian crossings, tactile signage and tactile floor maps, and pathways clear of obstructions or hazards.

But they also must contend with hostile environments, which lack all of these things, are not properly well lit, are too noisy, feature low hanging architectural features, have incorrectly printed Braille or have accessibility features that have been broken and not repaired, the list goes on.