Blindness has many definitions. Some define blindness as a complete inability to see, whereas some may state blindness still entails a differentiation between light and dark. The National Federation of the Blind encourages people “to consider themselves to be blind if their sight is bad enough – even with corrective lenses – that they must use alternative methods to engage in any activity that persons with normal vision would do using their eyes.” That is, blindness, in this case, is a condition in which someone requires an alternative way of doing things.
The United States Bureau of the Census question about “significant vision loss” considers both total or near-total blindness, as well as “trouble seeing, even when wearing glasses or contact lenses” as vision loss.
Legal blindness requires that central visual acuity is 20/200 or less in the better eye with the best possible correction, or a visual field of 20 degrees or less. There is no widespread definition for “visually impaired,” “low vision,” or “vision loss,” although there is a widely understood norm for these categories.
A common misconception is that a blind person cannot see anything, that someone who is blind sees nothing but empty black. The following series of images will portray different views a person with varying degrees of visual loss or impairment may experience.
A person who is not able to hear as well as someone with normal hearing – hearing thresholds of 20 dB or better in both ears – is said to have hearing loss. Hearing loss may be mild, moderate, severe, or profound. It can affect one ear or both ears and leads to difficulty in hearing conversational speech or loud sounds.
‘Hard of hearing’ refers to people with hearing loss ranging from mild to severe. People who are hard of hearing usually communicate through spoken language and can benefit from hearing aids, cochlear implants, and other assistive devices as well as captioning.
‘Deaf’ people mostly have profound hearing loss, which implies very little or no hearing. They often use sign language for communication.
Deaf-mute is a term that was used historically to identify a person who was either deaf and used sign language or both deaf and could not speak. The term continues to be used to refer to deaf people who cannot speak an oral language or have some degree of speaking ability, but choose not to speak because of the negative or unwanted attention atypical voices sometimes attract. Such people communicate using sign language.