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# Glossary

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## F

Field of Vision
The entire area that can be seen when the eye is directed forward, including what is seen with peripheral vision.

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## P

Point of Regard
The area that the user is viewing.

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## R

Ratio Measurement of Vision
Visual acuity is typically expressed using a ratio. 20/70 vision means that the person can only make out details at 20 meters what someone with good vision would be able to discern at 70 meters. Note that 20/70 is a ratio, so the metric is also applicable to 20 feet and 70 feet.
Rivers of White
In typography, rivers, or rivers of white, are gaps in typesetting, which appear to run through a paragraph of text, due to a coincidental alignment of spaces.
Source: wikipedia.org picture

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## V

Visual Acuity
A person's ability to make out details with their eye.
Visual Acuity is typically expressed as a ration where 20/20 means normal good vision.
To say that a person has 20/40 vision means that they see something at 20 feet (or meters) the way someone with good or correct vision would see that something at 40 feet (or meters).
Note that while this ratio measurement for visual acuity is referring to modest distances (like feet or meters), it works well enough for close-up reading as well (like with a book or computer screen).
Vision Impairment
The Centers for Disease Control and Prevention (CDC) define "vision impairment" to mean that a person's eyesight cannot be corrected to a "normal level." Vision impairment may result in a loss of visual acuity, where an individual does not see objects as clearly as the average person, and/or in a loss of visual field, meaning that an individual cannot see as wide an area as the average person without moving the eyes or turning the head. There are varying degrees of vision impairments, and the terms used to describe them are not always consistent. The CDC and the World Health Organization define low vision as a visual acuity between 20/70 and 20/400 with the best possible correction, or a visual field of 20 degrees or less. Blindness is described as a visual acuity worse than 20/400 with the best possible correction, or a visual field of 10 degrees or less. In the United States, the term "legally blind," means a visual acuity of 20/200 or worse with the best possible correction, or a visual field of 20 degrees or less. Although there are varying degrees of vision impairments, the visual problems an individual faces cannot be described simply by the numbers; some people can see better than others with the same visual acuity.
U.S. Equal Employment Opportunity Commission
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