Visual Acuity: What is 20/20 Vision?

Written by Dr. Melody Huang, O.D.

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What Does 20/20 Vision Mean?

20/20 is a term that describes having normal visual acuity or sharpness of vision. During an eye exam, your doctor will have you read letters on a chart to assess your visual acuity.

In other countries, optometrists use a visual acuity test distance of 6 meters. The equivalent to 20/20 is 6/6.

If you’re diagnosed with a refractive error, such as astigmatism, myopia (nearsightedness), or hyperopia (farsightedness), you won’t have 20/20 vision. You’ll need corrective lenses to fix the vision problem.

Interpreting the Numbers

The first 20 represents a standard testing distance of 20 feet. Typically, this number remains constant unless you use a different eye chart or test distance.

The second 20 refers to the quality of your visual acuity. The larger the second number, the poorer the visual acuity.

For example, if the smallest letter you can read corresponds to 20/40, someone with normal vision can see those letters at 40 feet. However, you can only see them at a distance of 20 feet.

Is 20/20 Vision Good?

20/20 vision means you have good visual acuity. However, this isn’t the only indicator of having healthy eyesight.

Other factors contribute to the overall vision quality, including:

Contrast sensitivity. The ability to distinguish between light and dark, such as locating a dark object against a similarly colored background.
Depth perception. This helps you judge objects in 3D and figure out how far away something is, such as when you’re driving. Good depth perception requires both eyes, so those with vision loss in one eye may have depth perception difficulties.
Peripheral vision. This is your indirect vision. It helps you see objects out of the corner of your eyes and gives a sense of the environment, such as walking into a crowded area.
Color vision. This helps you distinguish objects, such as seeing a red fruit against a green background, in locating food.
Eye movements and tracking abilities. These are essential in your daily life. From taking a walk to catching a ball to reading a book, accurate eye movements enable you to perform these activities efficiently.

How is Visual Acuity Measured?

Most ophthalmologists use the Snellen eye chart to measure visual acuity. When you view the eye chart, you may notice that different letter sizes correspond to varying levels of visual acuity.

A Snellen vision test starts with the biggest letter at the top, descending to the smallest letters at the bottom. Typically, the largest letter corresponds to a 20/200 letter size, while the smallest letters correspond to 20/10 letters.

Practical Methods for Conducting Visual Acuity Tests

Since you view the standard Snellen visual acuity chart at 20 feet, this type of chart is difficult to fit into a typical exam room. Many eye doctors use mirrors to simulate a 20-foot distance by reflecting the eye chart in the mirror.

This method is more practical than constructing a room 20 feet in length. Digital eye charts are a more modern solution to this problem.

The Process of Visual Acuity Examination

When you have an eye examination, your eye doctor begins by measuring your uncorrected visual acuity. This means you perform the test without glasses or contact lenses.

Then, they measure your visual acuity with your eyeglass prescription. This is your corrected visual acuity. It’s the test most people are familiar with when their doctor asks, “Which one is better, one or two?”

Approximately 35% of adults have natural 20/20 vision, while around 75% achieve 20/20 vision with corrective measures.² If you can’t read the largest Snellen letters on the chart, your optometrist will perform these additional visual acuity tests:

Count fingers (CF)
Hand motions (HM)
Light perception (LP)
No light perception (NLP)
Contrast sensitivity testing

How Can I Correct My Vision to 20/20 or Better?

If you're wondering how to achieve a 20/20 vision or even better, there are various vision correction options to explore. Your eye doctor can determine if eyeglasses or contact lenses can help you achieve at least 20/20 vision.

If conventional correction methods fall short or your vision quality with glasses or contacts isn’t optimal, other options are available, including:

1. Addressing Higher-Order Aberrations

In some cases, rigid gas-permeable contacts or digital high-definition glasses are necessary to alleviate higher-order aberrations.

These are irregularities typically in the cornea or the transparent front surface of the eye. They cause light-related distortions, such as:

Glare
Halos or starburst patterns around lights
Ghosting, shadowy, or blurry vision
Poor contrast sensitivity
Difficulty seeing in dim light

2. Exploring LASIK as a Solution

For those seeking a more comprehensive solution, wavefront-guided LASIK eye surgery is an option. This specialized LASIK procedure can reshape the cornea to correct higher-order aberrations effectively.

By customizing the treatment to your needs, wavefront-guided LASIK can provide superior vision quality for those dissatisfied with traditional glasses and contacts.

Many achieve vision better than 20/20 after undergoing LASIK surgery.¹ Consult an experienced eye surgeon to determine if you have higher-order aberrations and whether wavefront-guided LASIK suits you.

What Is Better Than 20/20 Vision?

Some people can see better than 20/20. However, 20/20 isn’t only the “perfect vision.”

If yours is 20/15, you can see one line of letters smaller than 20/20 on the eye chart. 20/10 vision is one line lower than 20/15, the smallest letter size most eye charts have.

Younger people are more likely to see better than 20/20 versus older ones. Your visual acuity tends to decline with regular age-related changes in your eyes.

Summary

Vision acuity tests like the Snellen chart are essential to routine eye exams. They help doctors determine your visual acuity and detect any potential vision problems.

While 20/20 vision is normal, many factors contribute to overall vision quality. These include contrast sensitivity, depth perception, peripheral vision, color vision, and eye movements.

Other options, such as wavefront-guided LASIK surgery, are available if you have difficulty achieving 20/20 vision with glasses or contacts. Consult your eye doctor to find the best solution and achieve optimal vision.

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