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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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.