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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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.