Generally, if people have 20/20 vision, they don’t necessarily have perfect vision. Having 20/20 vision simply means that you can see clearly at a distance of 20 feet what should normally be seen at that distance. You may still need glasses or contact lenses if you want to improve your near and intermediate vision, which is the ability to see clearly and sharply for things that are within arm's reach (16-30 inches away).

Having 20/20 vision means you can read the vision chart of a certain size from a certain distance - but that's not all it means

A good place to start understanding 20/20 vision is with an eye chart, which is a printed document consisting of rows of letters or numbers. The lines on the chart get smaller as you move down the page and are read from left to right. People speak of having 20/20 vision when their visual acuity is in the normal range. But here's the thing: having 20/20 vision only tells you about one aspect of your eyesight: how well you can see distant objects with no problems.

To have normal vision, it's not enough to just be able to read random numbers and letters on a wall chart. Even people with great eyesight don't see at full clarity 100% of the time—and if they're straining their eyes during any point in the day, they could be putting themselves through needless discomfort that may cause headaches and increase stress levels over long periods of time

A person with 20/20 vision should be able to see what an average person can see on an eye chart when they stand 20 feet away

To understand exactly what it means to have 20/20 vision, you have to know how visual acuity is measured. Visual acuity is the ability to see details at a distance. During an eye exam, your optometrist will ask you to read an eye chart that shows letters of various sizes. The size of the letters on the chart corresponds with the person's visual acuity; for example, a person with 20/20 vision can see at 20 feet what an average person can see at 20 feet. Someone with 20/100 vision can only see at 20 feet whereas someone with normal vision can see at 100 feet. People who are extremely far-sighted may even have results that are better than 20/20 — like being able to see objects clearly from 400 or 500 feet away!

An eye exam can determine whether your vision is 20/20.

An eye exam can be a good way to find out whether your vision is 20/20 and to diagnose other vision problems. During an eye exam, you’ll be asked to answer questions about your vision history and perform several tasks. For example, you may be asked to read letters of varying font sizes on a chart or identify colors of varying shades — all while sitting behind a machine called a phoropter. A phoropter looks like a pair of old-school headphones with an eyepiece attached. The tests you’ll perform using the phoropter are designed to assess the health and quality of your vision. Your doctor will use this information along with other assessments, such as tonometry and visual field testing, to make diagnoses. Findings from one or more of these tests can help them determine whether you have:

• astigmatism (irregularly shaped corneas)
• myopia (nearsightedness)
• hyperopia (farsightedness)
• presbyopia (age-related loss of elasticity in the lens)

You may need glasses even if your vision is 20/20 because glasses can correct other problems like color blindness and light sensitivity

Many people believe that if their vision is 20/20, then they don't need glasses. But this isn't true! 20/20 vision only means you have normal (or corrected-to-normal) visual acuity. There are other eye conditions that can be helped by wearing glasses, even if your vision is already 20/20.

For example:

Color blindness: If you're not able to accurately see certain colors, wearing glasses with tinted lenses can help you see those colors more accurately.

Light sensitivity: Some people have trouble looking at bright lights or certain color combinations of light. Glasses with special tinting can help them by filtering out the parts of the spectrum that cause problems for their eyes.