Some people talk about having 20/20 vision as if it means their eyesight is perfect. However, this merely indicates sharp visual acuity. To have good overall eyesight, you also need proper eye coordination, peripheral awareness, depth perception, focusing ability, and color vision.
How Do You Measure Visual Acuity?
Have you ever been asked to stand 20 feet from an eye chart, cover one eye, and read the smallest line of letters you can? This is a visual acuity test, one small part of a complete eye exam. The charts we use today were developed by Dutch ophthalmologist Herman Snellen in 1862. That’s why eye charts are also called Snellen charts, and 20/20 is considered a Snellen fraction.
What Does 20/20 Vision Mean?
Having 20/20 vision doesn’t necessarily mean you have perfect vision. Instead, it means you can read a particular row of letters on a Snellen chart from 20 feet away. Even with good clarity of vision, it’s still possible to have other eyesight problems.
Is 20/20 Vision the Best Vision You Can Have?
The goal for many is to achieve 20/20 vision, but some people have even better visual acuity. For instance, 20/15 vision means you can focus on letters from 20 feet away when someone with normal visual acuity would need to move within 15 feet to read them. 20/10 vision is even sharper!
Of course, Snellen fractions can also go in the other direction. If the second number is higher than 20, you have poor visual acuity. For example, 20/50 vision means you have to get within 20 feet to see what someone with 20/20 vision can see from 50 feet away. 20/200 vision is considered legally blind. It means everything on a Snellen chart is blurry from 20 feet away except for the big “E” at the top.
Why Do Some People Have Poor Vision?
Refractive errors affect visual acuity by preventing the eye from focusing at different distances. There are four main types:
- Nearsightedness (myopia) makes distant objects appear blurry. Eye charts measure this effectively.
- Farsightedness (hyperopia) makes near objects appear blurry. Even with 20/20 vision, you could still be farsighted and require reading glasses.
- Presbyopia makes it harder to see near objects as you get older.
- Astigmatism distorts objects, both near and at a distance.
Do I Need an Eye Exam?
If any part of your vision is blurry, visit an optometrist to receive a prescription for corrective glasses or contact lenses. Even if you have always had 20/20 vision, regular eye exams are still important to assess your eye health, monitor changes in your vision, and catch diseases like cataracts and glaucoma early when they’re easiest to treat.
Turn to Northwest Eye Center for the best eye care in Wheat Ridge, CO. Our certified eye doctors can provide everything from routine eye exams to LASIK eye surgery. We pride ourselves on offering the best customer service, quality care, and personalized attention. For help restoring or maintaining your eyesight, please contact us today!