The phrase “20/20 vision” is pretty common, but not everyone knows what exactly it means. Many people assume that your eyesight is perfect if you have 20/20 vision. The truth is, eyesight is complex, with many factors affecting how well you see. Your vision score is just one facet of your overall eyesight.
What is 20/20 Vision?
If someone has 20/20 vision, it means they have normal visual acuity. Visual acuity refers to how clear or sharp your vision is. Visual acuity is typically measured using a Snellen eye chart – the standard eye chart you see in every optometrist’s office, with the big letter E at the top.
20/20 vision means that you see something that is 20 feet away exactly as clearly and sharply as the average person should be able to see that object. The first 20 refers to how far away you are from the eye chart, and the second 20 refers to what the average person can see at that distance.
There are several things that can cause your visual acuity to be worse than 20/20. These include things like:
- Refractive errors, which affect the shape of your eye, such as astigmatism
- Farsightedness (hyperopia)
- Nearsightedness (presbyopia)
- Eye misalignment
- Eye conditions, such as glaucoma or cataracts
- Eye injuries, such as retinal detachment
About 35% of adults have 20/20 vision without any type of correction, like lenses or surgery. In many cases, the goal of corrective lenses is to get the wearer’s vision to 20/20. The number of adults with 20/20 eyesight increases to roughly 75% with the addition of corrective lenses.
Common Misconceptions About 20/20 Vision
There’s an assumption that 20/20 vision is “perfect” vision, but that’s simply not true. While 20/20 is ideal for visual acuity, vision itself is multifaceted. There are many other factors that can influence your vision, including:
- Astigmatism
- Color vision
- Depth perception
- Eye coordination
- Focusing ability
- Peripheral awareness/side vision
As a result, there are many reasons why someone with 20/20 vision may still need glasses. For example, someone could have 20/20 vision but trouble with depth perception, which would still require corrective lenses.
On top of that, 20/20 vision may be average, but your vision can actually be better than 20/20 vision. Some people have 20/15 vision, for example, meaning that they see an object that is 20 feet away as well as an average person would see that object if they were 15 feet away.
How Visual Acuity is Measured
Visual acuity is typically measured using a Snellen chart, or sometimes a variation of this chart. A standard Snellen chart has 11 rows of capital letters. The first line is often a large capital E. Each line of letters under the E gets smaller and smaller. Some tests use symbols or pictures to accommodate children or those who speak another language.
To test your visual acuity, you’ll stand 20 feet away from the chart and cover one eye. You then read out the smallest line of letters you can see. Then you’ll switch eyes and do it with the other, as your visual acuity may not be the same in both eyes.
There are other types of tests your provider may use in addition to or in lieu of a Snellen test. One of these is retinoscopy, an eye test that allows eye care specialists to measure refractive errors in the eyes. Another is autorefraction, which uses a machine to measure refractive errors. Both of these are ideal for patients who may have trouble communicating, like infants.
Vision Scores and Categories
A little over one-third of the population has 20/20 vision. Some people have vision that is better than 20/20, although it’s not particularly common. Those with visual acuity poorer than 20/20 can range from having mild vision loss to being totally blind.
The World Health Organization (WHO) categorizes visual impairment as follows:
- Mild vision impairment: 20/30 to 20/60
- Moderate visual impairment: 20/70 to 20/160
- Severe visual impairment: 20/200 or worse
- Profound visual impairment: 20/500 to 20/1,000
People with scores that are worse than 20/1,000 are considered to have near-total visual impairment. In the United States, someone whose vision cannot be corrected to better than 20/200 is considered legally blind.
Why Regular Eye Exams Are Essential
It’s easy for someone to find out they have 20/20 vision and assume they don’t need regular eye exams. However, eye exams are important for everyone, even those who have 20/20 vision.
Eye health can change silently, especially as you age. Having 20/20 eyesight doesn’t preclude you from age-related vision changes, such as presbyopia, a common, age-related vision condition in which your eyes gradually lose their ability to focus on nearby objects. Regular eye check-ups can also lead to early detection of eye problems, including glaucoma, cataracts, and diabetes-related issues.
Children should have their first eye exam between the ages of 6 to 12 months, with another exam between the ages of three and five. Kids and teens should have yearly eye exams.
Adults who are low risk should have an exam every two years or so, with annual exams after age 65. If you already have vision problems or are at risk for vision problems, you should have annual exams.
Things that may put you at risk for eye problems include:
- Having a family history of ocular disease
- Being diagnosed with conditions, such as diabetes or high blood pressure, that are linked to eye problems
- Taking prescriptions that can affect your eyes
- Working jobs that put strain on your eyes or can be hazardous to your eyes
- Having previous eye surgeries
- Being a part of certain racial or ethnic groups
If you’re not sure exactly how often you should be going in for eye exams, consult your eye care provider.
What Your Vision Really Says About Your Eye Health
Having 20/20 vision means that your visual acuity is normal, but it doesn’t mean it’s perfect. Vision is complex, and there are a number of things that can affect how well you see. Additionally, vision can change as you age, which is why it’s so important to have regular eye exams.
Barnet Dulaney Perkins has been providing high-quality eye care in Arizona for over 35 years. Contact us today to schedule an eye exam and learn how we can help you maintain your 20/20 vision.