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20/20 vision measures the sharpness of your vision when standing 20 feet away from an object. A lot of people think 20/20 vision is “perfect” vision, but it’s actually average vision. If somebody has 20/20 vision, they can see the same amount of detail as the average person.
In Europe, normal vision is considered 6/6, since they use meters instead of feet.
The most common test for visual impairment, the one you’re probably most familiar with, is the Snellen chart.
The Snellen chart, originally developed by Dutch ophthalmologist Herman Snellen, has been the standard introductory test for most eye exams for the last century and a half. This eye chart measured people’s visual acuity back in 1862, and lives on to this day!
Your optometrist will project this chart on a screen 20 feet away and have you read letters from each line, left to right. Each line is accompanied by a corresponding vision score (to the right).
Variations of the Snellen chart, especially the LogMAR chart, are also commonly used by eyecare professionals. The LogMar chart was developed by the National Vision Research Institute of Australia in 1976, to enable a more accurate assessment of visual acuity
| 20/15 vision | Better than average vision— able to make out details that someone with average vision could only see at 15 feet. |
| 20/20 vision | Average vision. |
| 20/40 vision | The requirement to pass a Driver’s License test. |
| 20/80 vision | Will greatly struggle with depth perception. Eyewear or corrective lenses are likely needed at this level. |
| 20/200 vision | Legal blindness— your visual field will be highly obstructed. |
Only about 35% of adults have perfect 20/20 vision without glasses, contact lenses, or corrective surgery. A study published in The Journal of the American Medical Association found that approximately 14 million Americans aged 12 and older have "visual impairment” — and that impairment tends to get worse over time.
A Global Burden of Disease study (see chart) found that as we get into our 50s and 60s, our vision loss begins to accelerate at a rapid pace. Globally, in 2020, an estimated 43.3 million people were legally blind, while 295 million had moderate to severe vision impairment. By 2050, those numbers are expected to balloon to 61 million and 474 million, respectively. But why does our vision get worse over time?
Routine annual eye exams with a licensed optometrist are a critical piece of preventative health care. Your optometrist will be able to detect eye diseases before you notice any symptoms and adjust your prescription to help ensure the best vision quality.
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