Most government agencies and health care institutions agree that legal blindness is defined as visual acuity (central vision) of 20/200 or worse in the best sighted eye or a field of vision (peripheral vision) limited to only 20 degrees. Visual acuity of 20/200 means that what the legally blind person can see at 20 feet, the average person can see clearly at 200 feet. When it comes to the field of vision, the average person can see 140 degrees without turning their head. If you are completely blind, you cannot see any light or shape. Among people with eye diseases, only about 15% can see nothing at all. If you are legally blind, you can still see, but not so clearly. Striem-Amit E, Gen M, Amedi A. „Visual acuity of congenital blind persons by visual sensory substitution for auditory. PLoS One. 2012;7(3):e33136.
doi:10.1371/journal.pone.0033136 Being legally blind affects your eyesight, but that doesn`t have to stop you from living a fulfilling life. What are the main causes of blindness? According to the National Eye Institute, there are four main causes of blindness in the United States. Basically, if it`s at least 20/70, can`t be corrected — even with touches, glasses, or surgery — and interferes with your daily activities, it can legally be considered a „visual impairment.“ There are many conditions that can cause legal blindness, but the most common are age-related eye diseases. Age-related eye diseases that are the main causes of low vision and blindness include: Blind Main Blind To be legally blind, you must have a visual acuity of 20/200. This means that even with glasses or contact lenses, you can only read the first letter at the top of the Snellen diagram, if at all. You can also be legally blind if you can see, but only in a very small window in your eye. Essentially, even if you can see, if you can`t see enough to function regularly, you can probably be considered legally blind. If you`re not completely blind yet, but your vision isn`t what it used to be, you probably fall into the category of visually impaired adults. Visual impairment is sometimes referred to as „partial blindness“, but because the term is not necessarily accurate, „visual impairment“ is preferred. To be legally blind, you must meet one of two criteria: visual acuity (visual acuity) and field of vision (the full range of what you can see without moving your eyes).
Like visual impairment, there are many different definitions of visual impairment. „Visual impairment“ is a broad term that describes a wide range of visual functions, from visual impairment to complete blindness. For more information on definitions of statutory blindness, see Assessment of Disability in Social Security, a publication of the Social Security Administration. In the United States, the Snellen Eye Chart (pictured left) is a test that ophthalmologists and optometrists use to measure a person`s visual acuity. It contains rows of letters, numbers or symbols printed in standardized graduated sizes. About 80% of blind people have residual vision. It can be difficult to understand how a person with a particular eye condition can see some things while not seeing others. While some people lose a lot of vision in a short time, others slowly lose vision. Many diseases that cause blindness begin to affect a certain part of vision and then progress to remove more vision. For example, macular degeneration initially affects a person`s central vision (the vision that makes us see straight ahead). Visual examples of what individuals might see if they have diseases such as macular degeneration, glaucoma, cataracts, diabetic retinopathy, and retinitis pigmentosa can be found on the National Eye Institute`s website at www.nei.nih.gov. Normal visibility is 20/20.
This means that you can clearly see an object from 20 feet away. If you are legally blind, your vision is 20/200 or less in your best eye or your field of vision is less than 20 degrees. That is, if an object is 200 feet away, you must stand 20 feet away from it to see it clearly. But a person with normal vision can stand at 200 feet and see this object perfectly. You may be surprised to learn that it is Uncle Sam, not the doctor, who determines whether you are legally blind. It varies from person to person. You may be able to see objects from a distance, but not from the sides of your eyes (peripheral vision). Or you may have good peripheral vision but difficulty seeing objects in the distance.
Few people today are completely blind. In fact, 85% of all people with eye diseases have some kind of vision; About 15% are completely blind. First, what does it mean to be „legally blind“? In most states, if you have less than 20/200 visual acuity that cannot be corrected with glasses/contact lenses, you are legally considered „severely visually impaired“ (which was called „legally blind“). But the trick here is not what you see „naturally“ (with the naked eye), but how well you see with your glasses or contact lenses. Despite such a high correction of myopic lens, if one or both of your eyes can see 20/40 or better, you are not „legally blind“. However, it`s easy to see how someone might feel this way when you`ve lost glasses somewhere! The Iowa Department for the Blind also serves people who are functionally blind. A person is functionally blind when they have to use so many alternative techniques to perform tasks that are normally performed with vision that their daily lifestyle is significantly altered. These alternative techniques could include reading a newspaper while listening to the phone or using Braille to read a book. Someone who is legally blind has corrected vision of 20/200 in their best eyesight. You may feel legally blind if you can`t see beyond one foot in front of you without wearing glasses, but as long as your vision can be corrected 20/20 with a visual aid like glasses, you`re not considered legally blind. A common test for visual acuity is Snellen`s eye chart.
Someone who is legally blind could simply read the top row of the chart, a capital E, while wearing corrective lenses. The line under the capital E is the line for 20/100. There are also tests that can measure between 20/200 and 20/100. Someone who can`t see the line for 20/100 but sees somewhere between 20/100 and 20/200 would still meet the government`s standard of legal blindness, which is why they are listed as „20/200 or less.“ A person with a visual impairment has difficulty performing ordinary tasks with vision – even with the best glasses or contact lenses. Did you know: The largest letter on the diagram (an E on most Snellen diagrams) is a 20/200 vision. If someone cannot distinguish this letter with his prescribed glasses, he is considered blind within the meaning of the law. Part 1 of the U.S. definition of legal blindness states this about visual acuity: The terms may also be used by health insurers to determine benefits and as part of the vision screening tests required by state motor vehicle departments (DMVs) when determining driver`s license eligibility. For safety reasons, people who are legally blind or visually impaired are generally not entitled to a driver`s licence.
Most surveys and studies show that the majority of people living in the United States with vision loss are adults who are not completely blind; Instead, they have what`s called poor eyesight. You may have heard the terms „partial vision“ or „partial blindness“ or even „poor eyesight,“ which are also used to describe low vision. However, these descriptions are no longer commonly used.