The visual disability

Visual disabilities include the blind and visually impaired.

Blind people

Blind people cannot use a mouse pointer, so they mainly use the keyboard to interact, and a screen reader to render what is happening on the screen.
Among the blind, we distinguish between those who were born blind and those who have lost their sight during their lives.
They will not necessarily use the same technical assistance. A person who is blind from birth will prefer Braille and therefore a tactile render, whereas people who have lost their sight during their lives will prefer a screen reader.

It will therefore be necessary to add alternatives to non-textual content (image, video, etc.), to allow good understanding of content structures (heading, list, page regions, etc.), to allow good understanding of rich interfaces (carousel, modal windows, autocompletions, etc.), and to prevent context changes.

Visually impaired people

Visually impaired people have extremely varied visual deficiencies.
They may not perceive colors (color blindness, Achromatopsia…), have a reduced visual acuity (blur, ametropia), a loss of peripheral or central vision (glaucoma, macular degeneration).

They use as assistance technologies a screen magnifier (physical or virtual), a screen reader (for the visually impaired) but also the customization of style sheets (text enlargement and line spacing, color customization…).

It will be necessary to take care not to give the information only by the color, to have sufficient contrasts on the contents, to allow the personalization of the CSS styles.