Visual Impairment Glossary

Visual 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. 

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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.