The range of vision for a person is infinite. You can see for miles and miles. On a clear day, you can see for up to 3 miles before the horizon due to the curvature of the earth. Yet you can see skyscrapers in a further distance than 3 miles due to no horizon obstruction.
Ever stare out at the ocean? The farthest point you can see is about 3 miles out. 6 miles: The average 747 passenger plane flies at about 6.6 miles up in the air. 50 miles: On clear days, city buildings can be seen from 50 miles away (if you're standing on the ground).
The human eye can see far beyond Earth's horizon. Earth's surface curves out of sight at a distance of 3.1 miles (5 kilometers).
A 6ft man standing and looking out to the horizon can see approximately 5km away, as the Earth's surface curves out of sight. But our ability to see extends well beyond the horizon. It also depends on the amount of dust and pollution in the air, which usually limits normal vision to less than 12 miles.
Various sources on the Internet suggest that a candle is visible to the unaided eye at distances varying from 3.6 to 30 miles.
For example, if your vision is 20/20, it means that from 20 feet away, you can see the smallest letters that should be seen at 20 feet. If your vision is 20/60, this means that from 20 feet away you can only see letters that would normally be visible at 60 feet.
The least distance of vision of a long-sighted person is 60 cm. By using a spectacle lens, this distance is reduced to 12 cm.
If you're legally blind, your vision is 20/200 or less in your better eye or your field of vision is less than 20 degrees. That means if an object is 200 feet away, you have to stand 20 feet from it in order to see it clearly. But a person with normal vision can stand 200 feet away and see that object perfectly.
Nearsightedness, or myopia, as it is medically termed, is a vision condition in which people can see close objects clearly, but objects farther away appear blurred. Myopia occurs if the eyeball is too long or the cornea (the clear front cover of the eye) is too curved.
The lens of your eye also hardens with age, which can lead to age-related farsightedness, called presbyopia. As the lens becomes more rigid, focusing on the retina directly is more difficult. This leads to blurred vision and trouble seeing things clearly close up.
It seems that the best eyesight ever reported in a human was in an Aborigine man with 20/5 vision! To give you an idea of how clear and far he could see, his vision measurement compares to the natural sight of eagles. From 20 feet, he could perceive the fine details that most people can only see from 5 feet away!
What is “Perfect” Vision? While 20/20 vision is considered to be perfect, it's not actually what we think of as perfect. Many people, mostly children, have better than 20/20 vision. Healthy eyes can easily go down to the 20/15 level with some accuracy.
Having 20/40 vision means that when you're standing 20 feet away from an object, you can see it just as clearly as a person with normal (20/20) vision can see an object that's 40 feet away.
Several sources say you can see a typical candle flame from 15 to 30 miles away, if you can see that far to begin with and it is completely dark.
While you might want to burn your candle all the way down to the very last speck of soy wax, you should only safely melt the wax to the last ½ inch.
As a group, the Aborigines have significantly better visual acuity than the Europeans. This was true for both monocular and binocular vision. Some Aborigines have acuities below the previous postulated threshold levels. Aborigines as a group also have the previous postulated threshold levels.
Mantis shrimps probably have the most sophisticated vision in the animal kingdom. Their compound eyes move independently and they have 12 to 16 visual pigments compared to our three. They are the only animals known to be able to see circular polarised light.
20/200 or worse, this is considered severe visual impairment, or severe low vision. 20/500 to 20/1000, this is considered profound visual impairment or profound low vision. Less than 20/1000, this is considered near-total visual impairment or near-total low vision.
Unfortunately, eyesight cannot be improved naturally and there is no way to change a refractive error, such as myopia, hyperopia, astigmatism, or presbyopia. These types of visual conditions can be treated with glasses, contact lenses, or refractive surgery. However, there can be other reasons for diminished eyesight.
Why is that? Answer: Some call this "second sight" which has a simple physiological explanation. As the lens of the eye hardens as we age (the predecessor of frank cataracts) it changes the way light is "bent" as it enters the eye much the way different prescriptions in a pair of glasses do.
Beginning in the early to mid-40s, many adults may start to have problems seeing clearly at close distances, especially when reading and working on the computer. This is among the most common problems adults develop between ages 41 to 60.