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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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.

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