Most people are familiar with the concept of 20/20 vision, or at least the phrase. Not as many know what it actually means to be seeing 20/20. When asked what 20/20 vision is, most people would answer, “Perfect vision,” or something similar. Though not totally incorrect, that isn’t true. In fact, it is nearly impossible to measure perfect vision because there is no such thing. Our vision and quality of sight changes based on the environment we are in, the amount of light, the distance to what we are looking at, glare, contrast, and countless other factors. Let’s break down what 20/20 vision actually is and how it relates to your sight.
Visual Acuity vs. Eyesight vs. Vision
When it comes to your “seeing,” there are three terms at play: visual acuity, eyesight, and vision. The first of these, visual acuity, is what is being measured by a measurement such as 20/20. Visual acuity refers to the sharpness or clarity with which you can see. It is a static measurement, or done when the person is standing still, and generally uses a chart with different sized letters or numbers (more on that later). Still, this type of test doesn’t measure how well you can see colors, moving objects, or objects with low contrast. From a physical standpoint, visual acuity is determined by how effectively your lens reflects light onto the retina, how sensitive the retinal nerves are, and how good your brain is at interpreting those signals.
Eyesight is a slightly broader term with a foggier definition. Sometimes, it is used interchangeably with the term visual acuity when referring to the ability to see. However, it can also refer to your range of sight, such as nearsightedness or farsightedness.
Vision is the broadest of the three terms. It includes visual acuity as well as a wide range of visual skills. For example, vision measures your ability to detect contrast, colors, depth perception, and moving object detection. So, when people refer to 20/20 vision, they are actually referring to 20/20 visual acuity. Though the phrase is technically incorrect, it probably isn’t going to change. Just keep in mind that being “20/20” is a measurement of just a small portion of your overall vision.
How Is Visual Acuity Measured?
Earlier, we mentioned that visual acuity is measured with a chart featuring differently sized letters or numbers. Most commonly, a Snellen Eye Chart is used. This chart is named after ophthalmologist Herman Snellen, the man who developed the measuring system in 1862. Over a hundred and fifty years later, this test is still one of the most commonly used techniques to measure a person’s visual acuity.
Measurements of visual acuity are documented as fractions like 20/20, 20/40, 20/60, and so on. The top number of the fraction refers to the distance between the person and the eye chart. You’ll notice that this number is nearly always 20. That’s because the patient stands 20 feet away from the chart in most American eye institutions. In some overseas clinics, the patient stands 6 meters away. On a standard Snellen chart, one of the smaller lines at the bottom, typically fourth from the bottom, is equal to 20/20 vision. As the lines of letters get bigger, so does the bottom number of the Snellen fraction. A person’s visual acuity is documented as the smallest row of letters they can read correctly.
What Does 20/30 Vision Mean?
If you’re interested in technicalities, you’ll find it intriguing that the bottom number isn’t just a random addition to the fraction. It refers to the distance a person with “normal” vision can see. For example, if you have 20/30 vision, you can see at 20 feet what a person with normal vision sees from 30 feet away. If you have 20/100 vision, you see at 20 feet what someone with normal vision sees at 100 feet.
What Does 20/10 Vision Mean?
If your visual acuity is poor, you won’t be able to read the smaller lines. But what if you can read the bottom line with crystal clarity? This means you have excellent visual acuity, often classified as 20/10 vision. In other words, you can see at 20 feet away what a person with “normal” vision can only see at 10 feet away.
Is 20/20 Vision The Same As Perfect Vision?
Nope. Ae we mentioned, there is no such thing as truly “perfect vision”. How well you can see depends on what you are looking at, the amount of light, motion, contrast, distance, and much more. If you have 20/20 vision, you have a good start. This means you can see things with a lot of contrast clearly when standing still. Even with 20/20 visual acuity you might struggle with seeing colors or reading things that are in motion, such as road signs. In short, 20/20 vision does not mean you have perfect vision in all situations, just one specific one.
Does Having 20/20 Vision Mean I Can Skip Going To The Eye Doctor?
Definitely not. Just because you have 20/20 vision does not mean you are free of all eye-related problems. This means you definitely don’t want to skip your visit to the eye doctor. Even with 20/20 visual acuity you could struggle with eye strain, trouble differentiating between colors, or problems with your peripheral vision. Even if you truly aren’t experiencing visual problems, it’s a good idea to have the eye doctor confirm this in case you experience a sudden change down the road.
Regular check-ups with your eye doctor also help ensure that you are free of eye-related diseases like glaucoma, cataracts, and dry eye. You can develop these dangerous and vision-threatening conditions whether or not you have good visual acuity. Your eye doctor will perform a vision screening and eye exam with each visit to detect these problems early if they arise. This allows for prompt treatment and better outcomes than if you were to skip an eye appointment and miss a diagnosis. Make sure you do what’s best for your eyes and visit your eye doctor routinely whether your not you’re seeing 20/20.