What does 20/20 vision mean?
Most of us have heard the term “20/20 vision” used to describe perfect sight. But what exactly does it mean? Why is it 20/20 and not 40/40? And what does it mean if your eye doctor says you have another number, such as 20/15?
The explanation for this particular pair of numbers is actually quite simple. Keep reading to find out what the numbers on your vision prescription mean.
How is 20/20 vision measured?
“Visual acuity” is the term that describes your ability to see details and shapes. Normal visual acuity means that you can see objects clearly from a distance of 20 feet.
Most eye care professionals use a standard Snellen chart to measure your vision. This familiar chart has rows of letters that decrease in size from top to bottom.
Your eye care professional will ask you to cover one eye and read the letters aloud, starting with the bigger letters at the top. Then you will repeat the test with the other eye, then with both eyes together. The smallest row of letters that you can read clearly determines your visual acuity.
*Did you know? In other parts of the world, eyecare professionals measure vision in meters instead of feet. Therefore, the goal is 6/6 vision, not 20/20.
Is 20/20 vision really perfect vision?
Although 20/20 vision is good, it doesn’t define perfect vision. You may have 20/15 or even 20/10 vision, which is considerably sharper than average. It means that you can see something clearly at 20 feet away that others can only see clearly from 15 or 10 feet away.
What does a higher bottom number, such as 20/30, indicate?
It simply means that you see less clearly than people who have 20/20 vision. There are varying degrees of reduced visual acuity:
- 20/30 to 20/60: Mild vision loss
- 20/70 to 20/160: Moderate low vision
- 20/200 or worse: Severe low vision
- 20/500 to 20/1000: Profound low vision
The purpose of eyeglasses and contact lenses is to bring your vision up to 20/20 clarity. Only 35% of adults have 20/20 vision without glasses. With corrective lenses, about 75% of adults obtain 20/20 vision.
Do other factors contribute to visual acuity?
Yes. How well you can see is influenced by many factors, including your eye coordination (how well your eyes work together) and the eye’s ability to focus. Your visual perceptual skills and ability to see different colors also influence visual acuity.
Does a vision test determine how healthy my eyes are?
No. Even if you have 20/20 vision, you could still have unhealthy eyes. In addition, other health problems can often be detected early due to vascular changes in the eye. That’s why a comprehensive eye exam is essential even for those who don’t need contacts or glasses.
If you’re looking for a great Chattanooga ophthalmologist, Allied Eye is here to meet all of your vision-related healthcare needs. Call or text us at (423) 855-8522 and schedule your appointment today!
