We have all heard someone say it before – “I’m legally blind without my glasses.”
Fortunately, this is untrue for the majority of people who make this statement. If vision improves below the legal blindness threshold while wearing glasses or contacts, then you’re technically not legally blind even without glasses.
Defining Legal Blindness
In the United States, the definition of legal blindness involves two criteria, however, only one needs to be met for an individual to be considered legally blind.
1. Visual acuity is 20/200 or worse in the better seeing eye with the best correction (i.e. glasses or contact lenses). This means a person with normal vision can read letters on the eye chart 200 feet away, whereas a person with legal blindness must be only 20 feet away from the chart to read the same thing.
2. The visual field is a total of 20 degrees or less. This is a measurement of peripheral vision or degrees of visibility to the side while looking straight ahead. A person can have 20/20 vision centrally and still be considered legally blind if the visual field is severely decreased. Peripheral vision helps with mobility and avoiding oncoming danger (traffic, flying objects, etc.).
Causes of Visual Impairment
According to the CDC, the leading causes of blindness include age-related macular degeneration, diabetic retinopathy, and glaucoma. Conditions that constrict peripheral vision or cause a tunnel vision effect include glaucoma and retinitis pigmentosa. Some causes of blindness can be sudden, while others are gradual and can take years to reach its worst point. Accidental eye injuries can be visually devastating depending on the severity of the injury. For this reason, it is important to use protective eyewear while playing certain sports and doing yard work.
Did You Know?
Individuals with profound vision loss, or blindness, are typically still able to perceive the presence of light versus dark environments. Most people do not experience total blindness where everything is completely dark. This is usually comforting to people with worsening vision conditions that may results in severe vision loss. When a person has total blindness and is unable to identify the presence of light, vision is recorded as “no light perception” or NLP.
Living with Vision Loss
Legal blindness is not a measure of functional vision. A person with severe visual impairment may still be able to do most of the same things that a person with good vision enjoys doing. Through the use of visual aids and vision rehabilitation, most people are able to live a fairly “normal” life. Low vision specialists are able to provide further resources and support for those with vision loss.