Visual disabilities can range from mild or moderate vision loss in one or both eyes to substantial or complete loss of vision in both eyes. Some people experience reduced or lack of sensitivity to certain colors or color blindness, as well as sensitivity to brightness.
- Color blindness - difficulty distinguishing between colors generally red and green, or yellow and blue, and sometimes the inability to perceive any color.
- Low vision - includes blurry vision, seeing only the middle of the visual field, seeing only the edges of the visual field, and clouded vision.
- Blindness - substantial loss of vision in both eyes.
Cognitive, learning, and neurological
Cognitive, learning, and neurological disabilities involve neurological disorders, as well as behavioral and mental health disorders. They impact how well people process and comprehend information.
- Attention deficit hyperactivity disorder (ADHD) - involves difficulty focusing on a single task, focusing for longer periods, or being easily distracted.
- Autism spectrum disorder (includes “autism,” “Asperger syndrome”) - involves impairments of social communication and the ability to interact.
- Mental health disabilities - Including anxiety, delirium, schizophrenia, mood disorders. Relating to web accessibility, these conditions may cause difficulty focusing, processing, and understanding information. The medications used frequently have side effects including blurred vision, hand tremors, and memory impairments.
- Memory impairments - involves limited short-term memory, missing long-term memory, or limited ability to recall language. Dementia is one among many different causes of memory impairments.
- Perceptual disabilities (also called “learning disabilities”) - involves difficulty processing sensory information such as auditory, tactile, visual. This includes impairments in reading or dyslexia, writing or dysgraphia, managing mathematic concepts or dyscalculia.
- Seizure disorders - includes different types of epilepsy and migraines, which may be in reaction to visual or audio stimulation.
Auditory disabilities include mild to moderation hearing impairment in one or both ears. Even partial loss or difficulty can be problematic in regards to audio content.
- Hard of hearing - mild to moderate hearing impairment in at least one ear.
- Deafness - hearing impairment that is substantial and uncorrectable in both ears.
Physical or “motor” disabilities are weakness and limitations of muscular control. These include: involuntary movements including tremors, lack of coordination, paralysis, limitations of sensation, joint disorders such as arthritis, pain that impedes movement, and missing limbs.
- Amputation - missing digits, limbs, or other parts of the human body.
- Arthritis - inflammation and damage to the joints.
- Paralysis - loss of control over a limb or other part of the body.
- Repetitive stress injury - involves injuries that occur to the muscles, bones, joints due to repetitive motion.
Speech disabilities include the inability to produce speech that is recognizable by other people or software. For instance, the volume or clarity of speech could make recognition difficult.
- Muteness - the inability to speak due to a multitude of reasons like mental disorders, cognitive impairments, or the ability to learn to speak.
- Dysarthria - weakness or paralysis of the muscles required to speak, including lips, lungs, throat, and tongue.
- Stuttering - speaking with continued involuntary repetition of sounds, especially initial consonants.
W3C: Diversity in Web Use