Vision: Low-Vision, Blindness, Deaf-Blind, Colour-Blindness
Visual disabilities range from mild or moderate vision impairments in one or both eyes (low vision or partial sight), to substantial and uncorrectable loss of vision in both eyes (blindness). It is estimated that about 2.3% of adult Canadians live with vision loss. Some people have reduced or lack of sensitivity to certain colours (colour blindness), or increased sensitivity towards excessive brightness in colours. These variations in perception of colours and brightness can be independent of the visual acuity. It is estimated that about 8 percent of the male population, and about 1 percent of females, experience colour blindness. People with visual disabilities access the web with:
- Screen readers that read electronic text out loud for blind users.
- Screen magnifiers with a keyboard rather than a mouse.
- Adjust browser preferences to enlarge text.
- Adjust browser preferences to enhance contrast.
Low vision users encounter a range of issues to do with design, styling, animation, movement and positioning. Shoppers with colour blindness will bookmark shopping sites where they can get reliable information on product colours and where they can override the colours, and not have to guess at which items were discounted. Imagine online shopping where discounted prices are indicated by red text and required fields on forms are indicated by red text. all of the text looks brown to somebody saddled with the protanopia eye condition. Solutions may use sufficient colour contrast, redundant information for colour (such as including names of the colours of products as well as showing a sample of the colour), adding text cues (such as an asterisk to discounted prices in addition to showing them in a different colour), and coding the website to allow override of default presentation.
- Font size – Small fonts can be especially problematic. Some people will bypass this using screen magnification software but many people who need larger fonts don’t have a need for screen magnification. As such it is important that web pages support text resizing within the browser. Text resizing is different from zoom which resizes the whole page.
- Poor contrast – Poor colour contrast can affect a wide range of users including many people with visual, cognition, and learning disabilities. It can also impact users on mobile devices in bright environments. Lack of sufficient contrast prevents people from being able to perceive the information that the content is attempting to convey. This in turn causes barriers to interaction, as users may be unable to identify their location on a page, the state of the interactive elements (links and controls), read text, or identify the content of images. The importance of good colour contrast can’t be understated as there are many more people with low vision than there are people who are blind.
- Relying on colour – Colour is a key component to web design improving not just aesthetic appeal and branding but also its usability and accessibility. However, some users have difficulty perceiving colour. People with partial sight often experience limited colour vision, and many older users do not see colour well. In addition, people using text-only, limited-colour or monochrome displays and browsers will be unable to access information that is presented only in colour.
- W3C video: Text-to-speech software
- W3C video: Colours with good contrast
- YouTube: How Does A Deaf-Blind Person Send Text Messages, Jerry Berrier
- YouTube: Painting a picture of the world through sound
- YouTube: Aira, a smartphone service providing instant access to visual assistance for those that are blind
- YouTube: Rethinking Colour and Contrast, Jared Smith
- YouTube: Accessibility in the Real World with Audio Description, The Paciello Group
- YouTube: How Blind People See the World
- NVISION Eye Centers: Navigating the Internet for the Visually Impaired
- Medium: Designing For Colour Blindness, Aaron Tenbuuren
- Digital Journal: Leading websites rated for accessibility for the visually impaired, Dr. Tim Sandle, November 2021