Few people are totally without sight. Most people who are classified as "blind" actually have remaining sight. Thanks to developments in low vision rehabilitation, they can make good use of what sight they have and improve their quality of life.
Anyone with noncorrectable reduced vision is visually impaired. The World Health Organization uses the following classifications of visual impairment.
When the vision in the better eye with best possible glasses correction is:
- 20/30 to 20/60, this is considered mild vision loss, or near-normal vision.
- 20/70 to 20/160, this is considered moderate visual impairment, or moderate low vision.
- 20/200 to 20/400, this is considered severe visual impairment, or severe low vision.
- 20/500 to 20/1,000, this is considered profound visual impairment, or profound low vision.
- less than 20/1,000, this is considered near-total visual impairment, or near-total blindness.
- no light perception, this is considered total visual impairment, or total blindness.
There are also levels of visual impairment based on visual field loss (loss of peripheral vision).
In the United States, any person with vision that cannot be corrected to better than 20/200 in the best eye, or who has 20 degrees or less of visual field remaining, is considered legally blind.
Visual impairments take many forms and exist in varying degrees. Visual acuity alone is not a good predictor of a person's vision problems. Someone with relatively good acuity (20/40) can have difficulty functioning, while someone with worse acuity (20/200) might not have any real problems performing daily activities.
Related Low Vision Links:
What Causes Low Vision?
Common Types of Low Vision
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Low Vision Devices
Low Vision Rehabilitation