Can anyone tell me exactly how far a healthy human eye can see?

Answer 1

Sight and perception are two different things.

you can see a star that is 1000 milliom light years away but a penny is hard to see after 50 feet. or so. PErception is key. That is why they use the 20-20 method. SOmeoene figured out waht "AVeerage was" adn compared what you can see to what he can see at 20 feet. If they are the same, than you have 20-20.

BP

Answer 2

Short answer: I doubt that anyone can absolutely answer that question.

Medium answer: You might get a better answer by asking something more specific, such as "How far away can a yellow tennis ball be and a healthy human eye still see it against a black background?"

Long answer: It depends on what you're trying to see and what's between the eye and the object, the properties of the object, the background behind it, etc. When you're looking at a star or a planet, you're seeing something that's pretty far away, right?

Answer 3

Depends on where the light of the star your looking at comes from. Think about it. If your seeing that star and it is a million light years away, that is how far. Normally you can only see to the horizon, but at night when you can see stars, the moon, etc. your question becomes a whole different issue.

Answer 4

Vision impairment means that a person's eyesight cannot be corrected to a "normal" level. It is a loss of vision that makes it hard or impossible to do daily tasks without specialized adaptations. Vision impairment may be caused by a loss of visual acuity, where the eye does not see objects as clearly as usual. It may also be caused by a loss of visual field, where the eye cannot see as wide an area as usual without moving the eyes or turning the head.

There are different ways of describing how severe a person's vision loss is. The World Health Organization defines "low vision" as visual acuity between 20/70 and 20/400, with the best possible correction, or a visual field of 20 degrees or less. "Blindness" is defined as a visual acuity worse than 20/400, with the best possible correction, or a visual field of 10 degrees or less. Someone with a visual acuity of 20/70 can see at 20 feet what someone with normal sight can see at 70 feet. Someone with a visual acuity of 20/400 can see at 20 feet what someone with normal sight can see at 400 feet. A normal visual field is about 160-170 degrees horizontally.

Vision impairment severity may be categorized differently for certain purposes. In the United States, for example, we use the term "legal blindness" to indicate that a person is eligible for certain education or federal programs. Legal blindness is defined as a visual acuity of 20/200 or worse, with the best possible correction, or a visual field of 20 degrees or less.

Visual acuity alone cannot tell you how much a person's life will be affected by their vision loss. It is important to also assess how well a person uses the vision they have. Two people may have the same visual acuity, but one may be able to use his or her vision better to do everyday tasks. Most people who are "blind" have at least some usable vision that can help them move around in their environment and do things in their daily lives. A person's functional vision can be evaluated by observing them in different settings to see how they use their vision. A functional vision evaluation can answer questions such as these:

Can the person scan a room to find someone or something?

What lighting is best for the person to do different tasks?

How does the person use his or her vision to move around in a room or outside?

Vision impairment changes how a child understands and functions in the world. Impaired vision can affect a child’s cognitive, emotional, neurological, and physical development by possibly limiting the range of experiences and the kinds of information a child is exposed to.

Nearly two-thirds of children with vision impairment also have one or more other developmental disabilities, such as mental retardation, cerebral palsy, hearing loss, or epilepsy. Children with more severe vision impairment are more likely to have additional disabilities than are children with milder vision impairment.

Answer 5

there is no distance limit (you can see light from stars that are billions of miles away).

Answer 6

I can see well for at least a mile....but is that normal?