Visual Impairment Glossary

Vision impairment and blindness, its causes, and assistive resources come with a huge range of terminology. Browse our glossary to learn the meanings of these terms. 

Fingers type on a BrailleNote touch
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Albinism is a genetic condition also called achromia, achromasia, or achromatosis. It occurs due to a deficit in the production in melanin and shows by the partial or complete absence of pigment in the skin, hair and eyes.

Aleatoric Music

This is refers to a type of music where some element of the composition is left to chance, or a part is left to the interpretation of the performer.

Assistive Technology

Assistive technology is a piece of equipment or system, that is used to increase, maintain, or improve functional capabilities of a child with a disability.
Assistive technology is a term that includes assistive, adaptive, and rehabilitative devices for people with disabilities.

Audible Light Probe

Light probes can be used by blind people, or those with reduced light perception, to tell how light or dark it is, if lights have been left on or the status of indicator lights/LEDs on appliances.


Binding Machine

A machine used to bind paper together using a spiral of wire or plastic that coils through a series of holes punched along one side of each page.

Blind Spot

This is the optically insensitive region in the retina where fibres of the optic nerve emerge from the eyeball. It has no rods or cones.


Total vision loss and conditions where individuals have to rely on vision substitution skills.

Body Awareness

Body awareness relates to knowing where your body is in space. It is linked to our proprioceptive system, (the input we get from our joints and muscles). Children who have poor body awareness may have a difficult time in functioning at a certain age level due to the difficulty that they may have when learning new tasks.


Is a type of written language for blind people, in which characters are represented by patterns of raised dots that are felt with the finger tips.

Braille Buttons

A three dimensional way to communicate a colour to people with visually impairment. The method matches the 16 common colours to shapes. Shaped coloured buttons provide a quick and simple tactile identifier for clothing, enabling a visually impaired person to be independently choose what to wear and be colour coordinated. Similarly shaped coloured pegs are used in specially designed board games. The SladeColour peg system with a ‘100’ pegboard is also used for the teaching of maths concepts.

Braille Code

This is a system of writing and printing for the blind in which arrangements of raised dots representing letters and numbers are identified by touch.

Braille Dymo Labeller

Braille Dymo Labeller is a portable Braille labeller.
The upper rim of the dial is brailled, the lower rim shows the standard print alphabet.

Braille Paper

A special kind of paper that is designed to be have braille printed (embossed) on it. The paper is thicker and sturdier than regular print paper.

Braille Tracking Sheet

Rows of braille dots (not necessarily actual letters) to encourage the ability to follow lines of braille accurately and detect changes in the pattern.

Braille Transcription

Braille transcription changes information from a print textbook into a braille version so that a student who is blind or has low vision gets the same benefits from the information as his or her sighted peers.


Compact and portable devices used by a student to take notes in class using either a braille. They can be used by braille learners to read books, write assignments, find directions, record lectures, and listen to podcasts. When connected to a monitor they display the print version of the braille being typed, allowing a non-braille reader to access the document.

A BrailleNote is a computer made by Human Ware for people with visual impairment. It has a braille keyboard, speech synthesizer, and a 32- or 18-column refreshable Braille display, depending on model.


Plastic round or square bumps that are used to mark items such as keyboard keys, phones etc. They are added to items that need to be felt more easily for those with visual acuity difficulties or who are blind.


Canaan Barrie

Canaan Barrie signs involve touching - on the body or hands - or movements close to the child.
Canaan Barrie is a system of communication through movement and touch, for children with multiple disabilities and a visual impairment who cannot communicate verbally or through traditional sign language.
The language was created by Mary Lee, a teacher at the Royal Blind School in Edinburgh, along with her former colleague Lindi McWilliam.

Contrast Sensitivity

Contrast sensitivity is an important measure of visual function, especially in situations of low light, fog or glare, when the contrast between objects and their background often is reduced.

Cortical Visual Impairment

Cortical Visual Impairment (CVI) refers to visual problems a child or adult may experience due to damage to the parts of the brain that deal with vision.  CVI can be referred to as 'Cerebral Visual Impairment', 'Cognitive Visual Impairment' or 'Visual Processing Disorder'.



This allows a student to write a paper in braille on a refreshable braille device, convert to ink print in Duxbury, and export to Word with all the emphasis of the original braille showing up in the Word file.



This refers to the ability of humans to detect objects in their environment by sensing echoes coming from those objects. By creating sounds – like tapping canes, stomping their foot, snapping their fingers, or making clicking noises with their mouths – people with this training are able to know where they are in space by interpreting the sound waves reflected back to them from objects around them, accurately identifying their location and size. This ability is used by some visually impaired people to navigate within their environment using auditory rather than visual cues.


Using braille translation software, a document can be embossed (printed) using an embossing machine. Embossers usually need special braille paper which is thicker and more expensive than normal paper. Embossers can be either one-sided or two-sided printers.


Fine Motor Activities

Fine motor skills are those that encourage a refined use of the small muscles controlling the hand, fingers, and thumb. The development of these skills allows someone to be able to complete tasks such as writing, drawing, and buttoning.

Functional Vision

A person’s ability to use vision in activities of daily living.


Gooseneck switch

Flat round switch mounted on a flexible arm

Gooseneck Swtich

A switch mounted on a flexible arm

Gross Motor Activities

Gross motor skills are movements involving the large muscles of the body. The development of gross motor skills starts as soon as a child is born. A visually impaired child often needs support to make sure these skills are developed.


Heat Fuser

A heat machine used in conjunction with Zytex2 paper to produce tactile diagrams. The printed diagram is passed through the heat fuser causing the black ink to swell up and form raised lines which can be examined using the hands.


Independent Living Skills

Independent living skills are skills necessary to live as independently as possible. Skills may include housekeeping, cooking, time management, shopping, laundry, and budgeting.



A computer screen reading program for Microsoft Windows that allows blind and visually impaired users to read the screen either with a text-to-speech output or by a refreshable Braille display.


Kay Pictures

The Kay Picture Test is a visual acuity testing system for children and for adults with learning difficulties. It is also used with young children not yet familiar with formal letters. The picture optotypes are fully researched and proven to accurately measure near and distance visual acuity in the same way as Snellen's letters.



Laminating sheets are used to cover and seal paper or card. The sheets are sealed with heat using a laminating machine.

LEA Vision Test System

This is a series of paediatric vision tests designed specifically for children who do not know how to read the letters of the alphabet that are typically used in eye charts. There are several variations of the LEA test which can be used to assess the visual capabilities of near vision and distance vision, as well as several other aspects of vision such as contrast sensitivity, visual field, colour vision, visual adaptation, motion perception, and ocular function.

Light Perception

These terms describe the ability to perceive the difference between light and dark, or daylight and nighttime. A person can have severely reduced vision and still be able to determine the difference between light and dark, or the general source and direction of a light.

The stereotypical assumption – that people who are blind or have low vision live in a type of "blackness" that sighted people see when they close their eyes – is generally not accurate.

Although every person sees differently, including persons with low vision, an individual who has light perception/projection can perceive the presence or absence of light. Some people describe light perception as knowing when a room light is on or off, or being able to walk toward a lighted lamp on a table in an otherwise darkened room.


A flat, translucent panel, set within a box with a light inside. Light pads make it easier to view objects or pictures in detail. They can be used to focus attention and increase clarity of viewing.

Low Vision

Low vision is a reduced level of vision that cannot be fully corrected with conventional glasses. It is not the same as blindness. Unlike a person who is blind, a person with low vision has some useful sight. Low vision usually interferes with the ability to carry out everyday activities such as reading. A person with low vision may not recognize images at a distance or be able to differentiate colours of similar tones.
Low vision is a degree of vision loss, where individuals can be helped significantly by low vision aids and devices.

Low Vision Aids

Many types of assistive devices are available to help people with low vision. These items include magnification devices and large print reading materials. Other communication aids include computer software and various other technological devices.


Maclure Test

This is a reading test specifically designed for children. Each age has been given a grade, numbered 1 to 7. If a child's reading ability is not equal to the average age, it can be recorded by the grade number. Within each grade print sizes N5, N6, N8, N10, N12, N14, N18, N24, N36, & N48 have been used. This test is designed to differentiate between children's ability to see and their ability to read.

Macular Degeneration

Macular degeneration is the main cause of severe vision loss in people over age 60. It occurs when the small central part of the retina, the macula, deteriorates.

Minolta Paper

A specialist paper onto which images can be printed and made into tactile diagrams.


Orientation and Mobility teaches safe, efficient, and effective travel skills to people of all ages and is specific to blindness and low vision.


Moon is considered a suitable reading medium for people who have been print readers and have lost their sight later in life. Many older people are discouraged by the finger sensitivity and effort required to learn braille; Moon enables those people to regain their enjoyment in reading.
Moon allows children with a severe visual impairment and additional learning difficulties to access literacy.

MS Word

This is a graphical word processing program used for typing. It is made by the computer company Microsoft. Its purpose is to allow users to type and save documents.


A concept relating to or involving several physiological sense.



This is a congenital or acquired persistent, rapid and involuntary movement of the eyeball, usually from side to side.


Ocean Drum

A percussion instrument that can mimic the sound of wave movements.

On body signing

Use of a manual sign that a signer places directly on the receiver's body. Its purpose is to provide an effective method of communicating tactilely to a child who is unable to access the sign visually.


A free image and photo editing software programme. This programme can be used to produce visually textured images which can be turned into tactile diagrams.

Peripheral Vision

All that is visible to the eye outside the central area of focus; side vision.


Perkins School for the Blind, in Watertown, Massachusetts, is the oldest school for the blind in the United States. It has also been known as the Perkins Institution for the Blind.
Perkins manufactures its own Perkins brailler and braille teaching tool, the Perkins SMART Brailler®.

Perkins Brailler

A "braille typewriter" with 6 keys corresponding to the dots of the braille code, a space key, a backspace key, and a line space key. It is used for producing documents in braille.

Pre-braille Skills

These are skills designed to increase tactual awareness and perception in individuals who will learn to read and write braille in the future.


Rain Stick

A long, hollow tube partly filled with small pebbles or beans that has small pins or thorns arranged on its inside surface. When the stick is held vertically the pebbles fall to the other end of the tube, mimicking the sound of rain falling.

Refractive Error

A refractive error means that the shape of your eye does not bend light properly, this creates a blurred image. The main types of refractive errors are myopia (near sightedness), hyperopia (farsightedness), presbyopia (loss of near vision with age), and astigmatism.


This is a layer at the back of the eye that contains light sensitive cells. These cells transmit nerve impulses that pass via the optic nerve to the brain, where a visual image is made.


This is inflammation of the retina of the eye.

Retinitis Pigmentosa

This is a chronic hereditary eye disease characterized by black pigmentation and gradual degeneration of the retina.


Screen reader

A software application that allows people with visual impairments to access computer information. Screen readers work with the computer’s Operating System to provide information about icons, menus, dialogue boxes, files and folders. A screen reader can provide feedback to the user via speech or braille.


A type of video tutorial allowing viewers to listen to the explanation of a demonstration/ lecture.

Self Help Skills

Providing the means to help an individual without relying on the assistance of others.

Sighted Guide

Sighted guide technique refers to a method by which a visually impaired person and a sighted person can walk together safely and comfortably.

Snellen Chart

A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862.

Social Story

Social stories are short descriptions of a situation, event or activity. They include specific information about what to expect in that situation and why, helping someone to prepare for that event.

Step by Step Switch

A communication aid with a big button,facilitating the recording of a series of messages, which can then be operated by the pupil.

Allows the recording of a series of messages which the user can step through in sequence. 


A screen magnifier, natural sounding speech and full screen reader with refreshable Braille synchronised or used separately.

Swell Paper

A specialist paper onto which images can be printed and made into tactile diagrams using a heat fuser.



Tacti-Mark is a liquid plastic that sets hard. It can be used as a teaching aid for writing letters, numbers, drawing pictures or outlining maps. It is useful for marking controls on cookers, washing machines, thermostats etc.

Tactile Markers

Added to braille labelling, you can add tactile markers to identify objects or areas. These may be in the form of tactile stickers, liquid plastic which sets hard, or anything that feels different to touch.


Activities involving braille patterns or raised lines and shapes to build skills necessary for reading braille print. Tracking encourages systematic exploration and searching for information on a page. It develops fine finer tactile sensitivity and discrimination skills.


Changing normal print materials into accessible formats for example; large print, digital audio, electronic text, braille, and images (tactile and large print).



The UK Association for Accessible Formats.


Vision Loss

A general term, including both total loss (Blindness) and partial loss (Low Vision), characterized either on the basis of visual impairment or by a loss of functional vision.

Visual Acuity

Visual acuity is a measure of the clarity of your central vision and the ability to distinguish shapes and details of objects. Distant vision is tested with a chart with differently sized letters read from a distance of six metres away. This is called the Snellen's Test Types.
The standard of your visual acuity depends on optical and neural factors like the sharpness of the retinal focus within the eye, the health and functioning of the retina, and the ability of the brain to make sense of those images.

Visual Field

This is the range within which objects are visible to still eyes it is also called field of vision.

Visual Field Loss

Visual Field Loss happens when damage occurs to any part of the visual pathway.
Visual field loss may be present due to disease or disorders of the eye, optic nerve, or brain. There are four main types of visual field loss:
1. Altitudinal field defects, loss of vision above or below the horizontal
2. hemianopia, loss of vision at the side
3. loss of central vision
4. loss at one side of the visual field for both eyes

Visual Impairment

A person is said to be visually impaired when their eyesight cannot be corrected to a “normal level”. It may be said that visual impairment is the functional limitation of the eye or eyes or the vision system.
Visual impairment is often defined as a best corrected visual acuity of worse than 6/18. The term blindness is used for complete or nearly complete vision loss.
Visual Impairment describes the condition of vision loss characterized by a loss of visual functions (such as visual acuity, visual field, etc.) at the organ level.


Wikki Stix

Wikki Stix are made of a strand of acrylic yarn enhanced with a non-toxic wax. They can be used to help blind children find their place in a page of text.



A specialist paper onto which images can be printed and made into tactile diagrams.

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