Facts about Low VisionVisual Acuity and Low VisionA Functional definition of low VisionLow Vision vs. Legal BlindnessUsing short Vision Optical and also Non-Optical DevicesVisual ImpairmentLight Perception and Light ProjectionTotal Blindness
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Facts about Low Vision
Most surveys and also studies show that the bulk of people in the United says with vision loss room adults who room not entirely blind; instead, they have what is referred to as short vision. Friend may have actually heard the state "partial sight" or "partial blindness" or also "poor vision" also used to define low vision. Those descriptions are no much longer in general use, however.
You are watching: What is meant by 20/70 vision
Here is one definition of low vision, related to visual acuity:Low vision is a condition caused through eye disease, in which visual acuity is 20/70 or poorer in the better-seeing eye and cannot be corrected or improved with regular eyeglasses. (Scheiman, Scheiman, and Whittaker)
Visual Acuity and also Low Vision
Visual acuity is a number that suggests the sharpness or clarity the vision. A intuitive acuity measurement of 20/70 way that a person with 20/70 vision who is 20 feet from an eye chart sees what a human being with unimpaired (or 20/20) vision deserve to see from 70 feet away.
20/70 can finest be interpreted by examining a conventional eye testing chart that you may have actually used in your very own doctor"s office during an eye examination.
In the united States, the Snellen Eye chart (pictured in ~ left) is a test that ophthalmologists and optometrists usage to measure a person"s distance visual acuity. It consists of rows that letters, numbers, or symbols printed in standardization graded sizes.
Your eye medical professional will ask you to check out or determine each line or row at a fixed distance (usually 20 feet), return a 10-foot experimentation distance is also used.
If you can read heat 8 (D E F ns O T E C) from 20 feet away while attract your constant glasses or call lenses, the medical professional records her vision (or intuitive acuity) together 20/20 with finest correction.
If the smallest publish you deserve to read is heat 3 (T O Z) from 20 feet far while wearing your continuous glasses or contact lenses, the doctor records your vision (or visual acuity) as 20/70 with ideal correction.
Please note: An yes, really Snellen Eye graph is much bigger than the one depicted here; therefore, it"s not recommended that you use this graph to test your very own (or a friend"s or family members member"s) intuitive acuity.
A Functional an interpretation of low Vision
Not every eye treatment professionals agree v an exclusively numerical (or visual acuity) description of low vision. Here"s one more — more functional — an interpretation of short vision:In various other words, low vision is "not enough vision to do everything it is you must do," which can vary from person to person.Most eye care professionals like to use the term "low vision" to explain permanently reduced vision the cannot be corrected with continual glasses, call lenses, medicine, or surgery.
Low Vision vs. Legit Blindness
"Legal blindness" is a definition used through the joined States federal government to identify eligibility because that vocational training, rehabilitation, schooling, special needs benefits, short vision devices, and also tax exemption programs. It"s not a functional low vision definition and also doesn"t phone call us very much at all around what a human being can and also cannot see.
Part 1 that the U.S. An interpretation of legal blindness states this about visual acuity:A intuitive acuity of 20/200 or less in the better-seeing eye with finest conventional correction (meaning with continual glasses or call lenses).
This is a 20/200 intuitive acuity measurement, associated with the Snellen Eye graph (pictured above):If you can only review line 1 (the big "E") native 20 feet far while put on your consistent glasses or contact lenses, the physician records her vision (or visual acuity) together 20/200 with best correction.
Part 2 the the U.S. An interpretation of legit blindness states this around visual field:OR a visual ar (the total area one individual deserve to see without moving the eye from side to side) the 20 degrees or less (also called tunnel vision) in the better-seeing eye.
This is a depiction of a constricted intuitive field:
For more information on the meanings of legitimate blindness, you have the right to read disability Evaluation Under society Security, a publication from the Social security Administration.
Using short Vision Optical and also Non-Optical Devices
Low vision optical, non-optical, and also electronic magnifying gadgets can make it feasible for friend to carry out a range of everyday tasks, including
To learn an ext about the many different species of reading alternatives that space available, view Reading, Writing, and also Vision loss on the VisionAware website.
Next Steps: What have the right to I Still perform If ns Am legit Blind?
Much choose low vision, over there are countless different interpretations of intuitive impairment. "Visual impairment" is a basic term that explains a wide range of visual function, from low vision through complete blindness.
Here is an instance of the sport in the ax "visual impairment" or "visually impaired" indigenous the human being Health company Levels of intuitive Impairment:
Moderate visual Impairment:Snellen intuitive acuity = 20/70 to 20/160
Severe intuitive Impairment:Snellen visual acuity = 20/200 to 20/400OR visual field of 20 levels or less
Profound intuitive Impairment:Snellen intuitive acuity = 20/500 to 20/1000OR visual ar of 10 levels or less
Like the hatchet "legal blindness," "visual impairment" is no a functional definition that tells us very much around what a human being can and cannot see. It is a category system, quite than a definition.
Light Perception and Light Projection
These terms describe the capacity to awareness the difference in between light and also dark, or daylight and also nighttime. A person can have severely decreased vision and still have the ability to determine the difference between light and dark, or the general source and direction that a light.The stereotypical assumption – that world who are blind or have low vision live in a form of "blackness" that sighted world see as soon as they close their eyes – is normally not accurate.Although every human being sees differently, including persons with low vision, an separation, personal, instance who has actually light perception/projection have the right to perceive the presence or absence of light. Some people describe light perception as knowing when a room irradiate is ~ above or off, or gift able come walk towards a lighted lamp on a table in one otherwise darkened room.
Total blindness is the complete lack of irradiate perception and form perception, and also is videotaped as "NLP," an abbreviation for "no irradiate perception."
Few civilization today are totally without sight. In fact, 85% that all people with eye disorders have some staying sight; roughly 15% are entirely blind.
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