This may result in difficulty distinguishing between red and green, or between yellow and blue. Sometimes it may mean an inability to perceive any color. Disabilities Deafness Deafness involves a substantial uncorrectable impairment of hearing in both ears. Some deaf individuals' first language is a sign language rather than a spoken and written language. If an individual has substantial uncorrectable losses of vision and hearing, the individual may be considered deaf-blind.
Paresis involves slight to extensive weakness in part of the body.
Either condition may be accompanied by pain which can further impede movement. Individuals with paralysis or paresis may have difficulty using a regular mouse or keyboard. They may not be able to activate commands that require multiple keystrokes simultaneously. They may need longer response times when dealing with interactive forms on Web sites. If an individual's muscles are tense and contracted, or if an individual has problems with coordination or involuntary movements, it may affect their ability to select keys on the keyboard or targets on a Web page.