Types of Disability
In the US alone, there are an estimated 30,000,000 people whose ability to use computers may be compromised by inaccessible design. Globally, around 8% of the people who use the worldwide web have some sort of disability. Disabilities fall into one of these categories:
- Visual Impairments - these can range from low-vision (including dim or hazy vision, extreme far- or near-sightedness, color-blindness, and tunnel vision, amongst others) to complete blindness. Poor choice of text size and color, and tasks that involve good hand-eye coordination (such as moving the mouse) can cause problems for these users.
- Movement Impairments - users with poor muscle control or weaknesses can find it hard to use a standard keyboard or mouse. For example, they may be unable to hold down two keys simultaneously, or they may be more likely to strike keys accidentally.
- Hearing Impairments - these can range from being able to hear some sounds but not distinguish spoken words, to profound deafness. Applications that convey important information by sound alone will cause problems for these users.
- Cognitive and Language Impairments - these can range from dyslexia to difficulties remembering things, solving problems or comprehending and using spoken or written language. Complex or inconsistent displays, or poor choice of words can make using computers difficult for these users.
- Seizure disorders - certain light or sound patterns can cause epileptic seizures in some susceptible users.