The U.S. National Library of Medicine reports that “blindness is a lack of vision. It may also refer to a loss of vision that cannot be corrected with glasses or contact lenses.” Though the concept of blindness commonly brings to mind a total loss of sight – a darkness that’s impenetrable, which is referred to as complete blindness – in reality, there are varying levels and degrees of blindness. Partial blindness is the term used to describe a limitation to vision.
Many people who are defined as legally blind are still able to see shapes, color and movement, but there can be some variation in what it means to be blind, legally or otherwise, and there are varying degrees of visual impairment:
Moderate visual impairment is defined as visual acuity (what you see straight ahead) of 20/70 to 20/160.
Severe impairment is 20/200 to 20/400 or 20 degrees or less of functional visual field. People whose vision acuity falls here are legally blind.
Profound impairment is 20/500 to 20/1000 or 10 degrees or less of functional visual field. This is also a level of legal blindness.
Another term related to vision loss is low vision, which means that vision loss is great enough that it makes performing everyday tasks difficult or impossible.
In all of these instances, there are certain eye diseases and conditions that make it more likely that you will struggle to see.
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