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20-40 Vision: What Does It Mean?

People with 20/40 vision can’t see perfectly without glasses or contacts. But they may be able to do most things, including drive, without corrective lenses. 

If you have 20/40 vision, you’re not alone. Only about 35% of adults have normal, 20/20 vision without glasses, contacts, or eye surgery. But if you want to see things sharper, your doctor can measure your vision and offer appropriate help. 

What Does 20/40 Vision Mean?

People with 20/40 vision must get within 20 feet to identify a letter that could be identified at 40 feet in a normal eye. 

The number 20/40 is a measurement of your visual acuity — how well you can identify numbers and letters on a standard vision chart (typically called a Snellen chart). The results can help guide your doctor’s choice of visual correction, as needed.

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How Does Your Doctor Determine If You Have 20/40 Vision?

Visual acuity testing is relatively simple and totally painless. 

Covering up one eye at a time, you’ll call out the letters you can see on a line of the Snellen eye chart

Then, your doctor or health care provider will place a correction lens in front of your eyes and ask you to call out data from the chart again. 

You’ll go through these steps with one eye and then the other. When you’ve finished the test, your doctor will have the information to create an effective prescription.

Is 20/40 Eyesight Nearsightedness or Farsightedness?

People with 20/40 eyesight must get closer to objects to see them clearly when compared to those with normal vision. They have nearsightedness, or myopia. 

About 30% of the world’s population has myopia. While the exact cause hasn’t been identified, experts think genetics and habits (such as staring at computers for long periods) are to blame. 

Is 20/40 Vision Bad?

People with 20/40 vision can’t see things as clearly as those with normal eyesight. The condition isn’t necessarily “bad,” as it isn’t life-threatening or contagious. It’s just the way your eyes work right now. 

Routine solutions, including glasses and contacts, can help to correct 20/40 vision. And sometimes, people with this visual acuity opt out of any lenses unless they’re doing something intricate that requires very precise vision. 

What Else Determines How Good Someone’s Vision Is?

A 20/40 visual acuity measurement covers how well you can see things in the distance. But many other factors play a role in how well you can see.

Those factors include the following:

  • Peripheral vision 
  • Eye coordination
  • Depth perception
  • Focusing ability 
  • Color vision 

These issues are often uncovered during a comprehensive eye exam performed by a doctor. The additional data can help your doctor determine what type of help will be most effective in improving your vision. 

Tools to Sharpen Your Vision 

If you want to see clearly, several options are available. Your doctor can help you determine which is right for you and your lifestyle. 


Glasses are a quick and impermanent way to change your vision. Slip them on when you want to see clearly, and take them off when you want to. If your vision changes, get new pairs without a lot of hassle. 

Glasses can be cumbersome, especially for people who play contact sports or swim. But they don’t require surgery or ongoing maintenance, so they could be attractive for many people. 

Contact Lenses 

Contacts sit on the surface of your eye, so they’re a private way to fix your vision. No one will know you’re wearing them, and they won’t interfere with sports and other activities. 

Contacts must be cleaned properly, or they can lead to corneal ulcers. In rare cases, these eye sores can lead to blindness. 

Make sure you know how to clean your lenses before you wear them. 


LASIK and other surgeries may be options to correct your vision more permanently. 

LASIK reshapes the cornea so light refracts as it should, and images appear sharper. Many people enjoy the freedom they gain after LASIK since they no longer rely on glasses or contacts.

Lifestyle Changes to Protect Your Vision 

Simple steps you take every day could help your vision stay sharp. Try incorporating these into your daily life:

Stop Smoking

Smoking is a leading cause of age-related macular degeneration (ARMD). An Australian study estimated that one in five cases of ARMD could be linked to smoking. 

Smoking also causes cellular change, vascular constriction, and oxidative stress.

Wear UV Protection

Put on your sunglasses. Protecting your eyes from UV light can protect your vision and reduce your risk of developing cataracts.

Get Regular Eye Exams

Visiting with your doctor regularly could mean catching illnesses when they’re easier to treat. Never skip your appointments, and be honest with your doctor about how well you can see. 

Rest Your Eyes

Some people struggle to see clearly when they strain their eyes by reading, knitting, or performing some other form of close work. Look up periodically, and remember to blink. These breaks could help your eyes focus better. 

FAQs About 20/40 Vision

Does someone with 20/40 vision always need glasses?

No. Some people with 20/40 vision don’t wear glasses all the time. But according to the Centre for Vision in the Developing World, a 20/40 score can make some things difficult, such as reading menus on a blackboard, deciphering flight details at the airport, or watching movies with subtitles. It may be challenging to read the fine print of a recipe or instruction manual. 
If this is true for you, you may want to invest in some corrective lenses. Your corrective eyewear would give you 20/20 vision.

Can a person with 20/40 vision drive without vision correction?

In most states, you don’t need to wear vision correction if your acuity is 20/40 or better. But correction could help you read signs, make quick decisions, and become an all-around better driver.


  1. What Does 20/20 Vision Mean? (January 2022). American Academy of Ophthalmology.

  2. Myopia (Nearsightedness). American Optometric Association.

  3. All About the Eye Chart. (March 2022). American Academy of Ophthalmology.

  4. Visual Acuity. American Optometric Association.

  5. Focusing on Contact Lens Safety. (October 2019). U.S. Food and Drug Administration.

  6. Eye Diseases. Tobacco in Australia. (May 2020). Cancer Council Victoria.

  7. Delivering Glasses to 2 Billion People Who Lack Access to Conventional Eye Care Services. (August 2016). Centre for Vision in the Developing World.

Last Updated September 29, 2023

Note: This page should not serve as a substitute for professional medical advice from a doctor or specialist. Please review our about page for more information.

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