Disability is a state of being human in which full and effective participation in typical societal activities is limited. For example, students who are blind or have low vision may be prevented from attaining a similar level of education due to the lack of educational materials adapted to their needs. Similarly, people with mobility impairments may face barriers to daily mobility due to missing infrastructure like evenly leveled sidewalks and curb cuts.
Accessibility is a quality of interactions between individuals and the world being enabled. For instance, between blind persons and educational materials, or wheelchair users and sidewalks. When human-world interactions are accessible, a person can effectively carry out intended activities without challenges, like learning and walking/locomotion. In contrast, inaccessible interactions occur when factors prevent effective engagement with the world.
Disability is not the same as a health condition or impairment (WHO, 2022). Health conditions refer to medically diagnosed conditions such as deafness. Such conditions could contribute to disability. For example, deaf individuals may struggle to get information from news channels that deliver content only through audio. However, discussions around disability focus more on removing barriers to accessibility, regardless of the underlying health condition or impairment. This perspective—which separates disability from the medical scope—is called the social model of disability. Medical and rehabilitation interventions treat conditions at the individual level, while accessibility work modifies environments and systems to remove barriers.
This course explores the accessibility of digital products and how computational tools can enhance interactions between disabled individuals and their environments. We will examine why accessibility matters not just ethically, but also practically and legally.
Before we discuss digital product accessibility, let's first understand some types of health conditions and impairments that can lead to disabilities without appropriate accessibility considerations and interventions.
A typical Snellen chart that is frequently used for visual far acuity testing. (Wikipedia)
Blindness and low vision affect how people access visual information from their environment, such as computer and smartphone displays. Visual impairments exist on a spectrum. Some people are totally blind, with no visual perception or only minimal perception of color and light. Others have partial vision, with varying degrees of acuity, visual field, and other characteristics.
Regardless of where they fall on this spectrum, people with visual impairments could benefit from accessing information through non-visual channels. Technologies like screen readers and magnifiers help individuals who are blind or have low vision consume information, while advanced computer vision technologies can help them understand their physical surroundings.
Example of an Ishihara color test plate. The Ishihara test detects red–green color deficiencies. (Wikipedia)
Color blindness or color vision deficiency is the decreased ability to see color and distinguish shades of color. The severity of color blindness ranges from mostly unnoticeable to full absence of color perception. This kind of visual impairments lead to challenges such as reading visual information written in certain color combinations.
Motor impairment is the partial or total loss of function of a body part, usually a limb. This manifests as muscle weakness, poor stamina, lack of muscle control, or total paralysis. Motor impairments are often associated with neurological conditions such as cerebral palsy, Parkinson's disease, stroke, and multiple sclerosis. The resulting lack of dexterity and mobility can create challenges when interacting with computing devices. For example, people with motor impairments may find it difficult to use a mouse, type on a keyboard, or perform precise touch gestures on screens. Assistive technologies such as adaptive keyboards, mouth-operated joysticks, and eye-tracking systems help individuals with motor impairments access and control digital products more effectively.
Hearing loss is a partial or total inability to hear. In children, hearing problems can affect the ability to acquire spoken language and develop communication skills. In adults, hearing loss can create difficulties with social interaction, workplace communication, and accessing audio information from digital devices and environments. Hearing loss is increasingly prevalent because it often develops gradually with age and the world is aging. It can range from mild difficulty hearing certain frequencies to profound deafness. People with hearing loss may benefit from assistive technologies such as hearing aids, cochlear implants, and captioning services. In digital contexts, accessibility features like captions, transcripts, and visual alerts help ensure that audio content is accessible to individuals with varying degrees of hearing loss.