Visual
Achromatopsia
Achromatopsia is a rare visual condition characterized by an inability to perceive colors. Individuals affected by it primarily see in black, white, and shades of gray. This condition results from an abnormality in the cones, the photoreceptor cells in the retina responsible for color vision.
- Nature of disability : Congenital
- Age group concerned : All
- Number of people affected : 1 birth in 60,000
Symptoms
Total or partial absence of colour perception. Black and white vision
Examples of obstacles encountered during navigation
- Images, controls and other structural elements that do not have equivalent text alternatives. (e.g. Daltonian without a textual colour alternative)
- Text, images and layouts that cannot be resized or that lose information when resized.
- Missing visual and non-visual guidance, page structure and other navigation aids.
- Video content that does not have text or audio alternatives, or an audio description track.
- Inconsistent, unpredictable and overly complicated navigation mechanisms and page functions.
- Text and images with insufficient contrast between foreground and background colour combinations.
- Websites, web browsers and authoring tools that do not support the use of custom colour schemes.
- Websites, web browsers and authoring tools that do not provide full keyboard support.
Solutions for accessibility
- Better colour contrast
- Daltonian’ colour variation to make them easier to understand
- Text alternative to incomprehensible content
- Screen magnification software to enlarge text on websites to an appropriate font size;
- People with visual impairments generally rely on modifying the presentation of web content into forms that are more usable for their particular needs. For example by :
- Enlarging or reducing the size of text and images ;
- Customising font, colour and spacing settings;
- Listening to text summaries of content;
- Listening to audio descriptions of multimedia videos;
- Reading text in updateable Braille.
- Large computer screen with high resolution and brightness.
- Developers must ensure that the presentation of web content is independent of its underlying structure and that the structure is correctly coded so that it can be processed and presented in different ways by web browsers and assistive technologies.
- Some people only see small portions of content at a time or perceive colours and design differently. Some people use custom fonts, colours and spacing to make content more readable, or navigate content using the keyboard only because they cannot see the mouse pointer.