What blindness means
At a glance
Legally blind, in the United States
20/200 or less in the better eye with correction, or a field no wider than 20 degrees
The Social Security definition, used for benefits and services.
Low vision
Sight that glasses, contacts, medicine or surgery can't fully fix
And that gets in the way of everyday activities. The National Eye Institute's definition.
A red-and-white striped cane
Means the person is deafblind
They may not hear a shouted warning or a car.
White Cane Safety Day
October 15
Set by a joint resolution of Congress in 1964; the National Federation of the Blind calls it White Cane Awareness Day.
Blindness is a range
Between full sight and no light at all sit most of the people the word "blind" describes. Where someone is on this line says nothing about what they can do.
Full sight
With or without glasses
Standard vision, or vision that glasses or contacts bring back to standard.
Low vision
Everyday tasks are harder
Sight that standard treatment can't fully fix. Reading, faces, stairs or night travel take tools and strategies.
Legally blind
A line drawn for services
The point at which US law opens benefits, rehabilitation and protections. Many people here read with magnification and travel on their own.
Light perception
Light and dark, not shapes
Enough to tell a lit window from a wall, which still helps with orientation.
No light perception
Total blindness
No visual input at all. The one most people picture, and only one point on the line.
Why the words matter
"Blind" on a form, "legally blind" at the doctor's office and "blind" in conversation describe different things. For inherited retinal disease, the useful questions are what kind of sight is affected and what that changes day to day, which is what the rest of this page is about.
Kinds of vision loss
Two people with the same label can see very differently, because retinal conditions take different parts of sight.
Central vision
Reading, faces and fine detail get hard while the edges stay. Comes from the macula.
Stargardt disease, Best disease and other macular dystrophies
Side vision
The outer field narrows, so things at the corners of the eyes disappear first; the center can stay sharp for a long time.
Retinitis pigmentosa, Usher syndrome
Night vision
Dim light that others manage becomes unusable; often the first change in rod conditions.
Retinitis pigmentosa
Color
Colors fade or vanish when the cones don't work.
Achromatopsia, cone dystrophy
Light sensitivity
Bright light is painful or washes everything out; some people see better in dim rooms.
Achromatopsia, cone dystrophies
The legal line
Legal definitions exist to decide who qualifies for services. They are thresholds, not descriptions of what a person sees.
Legal blindness
United States, Social Security definition
Sharpness
Central visual acuity of 20/200 or less in the better eye with a correcting lens. At 20 feet you see what a person with standard sight sees at 200.
Or field
A visual field whose widest diameter is no greater than 20 degrees, whatever the acuity. Side vision is gone even if the center is sharp.
What it opens
Disability benefits, vocational rehabilitation, state blind services and tax provisions. See our
state blind services directory
.
Low vision
National Eye Institute definition
What it is
A vision problem that makes it hard to do everyday activities and that can't be fixed with glasses, contact lenses, or standard treatments like medicine or surgery.
What helps
Vision rehabilitation: a specialist helps you learn to live with the vision you have, with lighting, magnification, training and technology.
Where to start
Ask your eye doctor for a low-vision evaluation, and see our
living with low vision
guide.
The white cane
A tool first, a signal second. It finds steps, curbs and obstacles before the feet do, and it tells everyone else to give the person room.
Three kinds of cane and the two markings worth knowing. Orange stands in for red. Drawing, not to scale.
Long cane
Reaches the ground a step or two ahead and is swept side to side to find curbs, steps and obstacles. The everyday travel tool, taught by orientation and mobility specialists.
Identification cane
Shorter and lighter; carried to tell others the person has low vision rather than to find obstacles.
Support cane
A walking cane in white, for people who need balance support and want their vision loss to be visible.
The markings
In the United States any white cane, with or without a red band near the tip, signals that the user is blind or has low vision. Red-and-white stripes along the length signal that the person is deafblind, with both sight and hearing affected.
If you meet someone with a cane
Simple courtesies that keep people safe and treat them as adults.
Driving, stop fully when a cane user or guide dog is at a crossing. State white cane laws require drivers to yield.
Ask before helping, and take no for an answer.
Say who you are and speak to the person, not to whoever is with them.
Give directions in words: "the door is ahead on your left", not "over there".
Never grab an arm, and never touch or move the cane or a guide dog.
If the cane is striped, the person may not hear you: a light touch on the arm, then words.
Six things people get wrong
The myth, struck out, and what is true.
Myth: Blind means total darkness. Reality: Many people who are blind see something: light, shapes, movement, color, or clear detail in one part of the field.
Myth: A white cane means the person sees nothing. Reality: Many cane users have usable vision and carry the cane for obstacles their sight misses, or to signal in unfamiliar or dim places.
Myth: Legally blind means no vision. Reality: It is a line drawn for services. Many people past it read with magnification, recognize faces up close and use a phone like anyone else.
Myth: You are either sighted or blind. Reality: Sight runs along a range, and inherited retinal disease moves people along it slowly, often over decades.
Myth: Everyone who is blind sees the same way. Reality: Some lose the center, some the edges, some the night, some color. The condition decides, and so does its stage.
Myth: People who are blind can't work, read or use technology. Reality: With training and tools, people with significant vision loss study, work, raise families and travel. Screen readers, magnification and voice assistants are built into the phones already in their pockets.
Sources
Social Security Administration, 20 CFR 404.1581, Meaning of blindness as defined in the law (statutory blindness: 20/200 or less in the better eye with a correcting lens; visual field no greater than 20 degrees).
National Eye Institute, Low Vision (definition; vision rehabilitation).
National Federation of the Blind, White Cane Awareness Day (joint resolution of Congress, 1964, designating October 15 as White Cane Safety Day).
American Council of the Blind, White Cane Laws for States (state statutes requiring drivers to yield to pedestrians with a white cane or guide dog).
Deafblind UK, Red and white canes (the striped cane as the sign of deafblindness).
National Eye Institute, Retinitis Pigmentosa; MedlinePlus Genetics, Achromatopsia and Stargardt macular degeneration (the kinds of vision loss and example conditions).