Sensory impairment

Visual impairment and blindness

There are 4 levels of visual function:

  1. normal vision
  2. moderate visual impairment
  3. severe visual impairment
  4. blindness

Moderate visual impairment (2) combined with severe visual impairment (3) are grouped under the term “low vision”. Numbers 2, 3 and 4 taken together represent all visual impairment.

Read more about visual impairment on the website of the World Health Organisation.


Hearing impairment and deafness

The term ‘hearing loss’ is used to cover all kinds of deafness. 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. They usually communicate through spoken language and can benefit from hearing aids, cochlear implants and other assistive devices as well as captioning. (Captioning is the text version of speech and other sound that can be provided on television, DVDs, online videos, and at cinemas and theatres.) People with more significant hearing losses may benefit from cochlear implants.

“Deaf” people mostly have profound hearing loss, which implies very little or no hearing. They often use sign language for communication.

Read more about hearing impairment on the website of the World Health Organisation.


Assistance dogs

Guide dogs

Guide Dogs assist blind and visually impaired people by avoiding obstacles, stopping at curbs and steps, and negotiating traffic. The harness and U-shaped handle fosters communication between the dog and the blind partner. In this partnership, the human’s role is to provide directional commands, while the dog’s role is to insure the team’s safety even if this requires disobeying an unsafe command.

Hearing dogs

Hearing Dogs assist deaf and hard of hearing individuals by alerting them to a variety of household sounds such as a door knock or doorbell, alarm clock, oven buzzer, telephone, baby cry, name call or smoke alarm. Dogs are trained to make physical contact and lead their deaf partners to the source of the sound.

Assistance dogs organisations


Sign language

Sign Language is visual-gestural mode of communication that uses hand shapes, facial expressions, gestures and body language mainly used by people who are deaf. Worldwide, there are about 70 million deaf people who use sign language as their first language. Each country has one or sometimes two or more sign languages.

For example in the UK, British Sign Language (BSL) is the most widely used method of signed communication. There are some 150,000 Deaf adults and children in the UK who use BSL and for 70,000 of them BSL is their preferred means of communication. BSL is a complete language with its own structure and grammar, which are completely different from English. BSL was officially recognised by the government as a language in 2003.

Just as spoken languages, sign languages vary greatly between countries and ethnic groups. Today, International Sign is used widely at international meeting where participants do not share one common sign language.

Read more about Sign Language on the World Federation of the Deaf website.