Explaining 20/20 Vision: What It Means and How It's Measured

20/20 vision is commonly referred to as “normal” or standard vision, a measure of visual acuity. When an individual has 20/20 vision, it means they can clearly see an object 20 feet away. This measurement comes from the Snellen Eye Chart, where each row of letters corresponds to a level of visual clarity. However, it’s important to note that 20/20 vision only refers to sharpness of sight at a distance and doesn’t account for other aspects like depth perception, color vision, or peripheral awareness. Thus, having 20/20 vision doesn't necessarily mean you have “perfect” vision.

What is Perfect Vision?

While 20/20 vision is often equated with perfect vision, the truth is, perfect vision is more comprehensive than just clarity at a distance. True visual perfection involves several other elements beyond acuity. These include good depth perception, color accuracy, peripheral vision, and the ability to focus both near and far. Someone with 20/20 vision may still need assistance for reading or have trouble with low-light conditions, which are not measured by standard visual acuity tests. Therefore, perfect vision includes a range of visual abilities that enable a person to see clearly in all situations, not just at 20 feet.

How Vision Is Tested

Testing vision involves various methods and tools, but one of the most common tests used to measure distance vision is the Snellen Eye Chart. The process typically includes:

Snellen Eye Chart Test: Letters of varying sizes are displayed 20 feet away, and the person reads the smallest line they can see clearly.
Refraction Test: Determines the correct prescription for glasses or contacts.
Visual Field Test: Measures peripheral vision.
Retinoscopy: Used for detecting refractive errors.
Slit-lamp Examination: Examines the front part of the eye (eyelids, cornea, iris, lens).
Color Blindness Test: Assesses the ability to see different colors.

What Vision is Better Than 20/20

Vision sharper than 20/20, such as 20/15 or even 20/10, means that a person can see details at 20 feet that someone with normal vision can only see at 15 or 10 feet, respectively. People with 20/15 vision or better can discern smaller letters or objects from further distances. While this sharper-than-average vision is desirable, it is not always necessary for day-to-day tasks. Many athletes, pilots, and others in fields requiring exceptional vision strive for or naturally possess better-than-20/20 vision.

Different Types of Visions

Type of Vision	Description	Difference from 20/20 Vision
Myopia (Nearsightedness)	Objects close are clear, but distant objects are blurry.	Distant vision is worse than 20/20.
Hyperopia (Farsightedness)	Distant objects are clear, but close objects are blurry.	Close-up vision is weaker.
Astigmatism	Distorted or blurred vision due to irregular curvature of the cornea.	Both near and far vision may be affected.
Presbyopia	Age-related difficulty in focusing on close objects.	Often affects near vision more significantly.
Normal Vision (Emmetropia)	Clear vision at all distances.	Matches or exceeds 20/20 vision

Corrective Measures for Non-20/20 Vision

Corrective Measure	Description
Glasses	Lenses are prescribed to correct refractive errors like myopia, hyperopia, and astigmatism.
Contact Lenses	Work similarly to glasses but sit directly on the eye’s surface.
LASIK (Laser Surgery)	Reshapes the cornea to correct refractive errors, often leading to 20/20 or better vision.
Photorefractive Keratectomy (PRK)	A laser procedure that reshapes the cornea to improve vision, similar to LASIK but with a longer recovery time.
Phakic Intraocular Lens Implants (IOLs)	Implanted lenses that can correct severe refractive errors without removing the natural lens

What Does 20/20 Vision Mean - Frequently Asked Questions

How do you convert an eye prescription to the 20/20 scale?

Eye prescriptions (e.g., -2.00 or +2.50) cannot be directly converted to the 20/20 scale, but they both measure different aspects of vision. A Snellen chart measures visual acuity (e.g., 20/20 or 20/40), while a prescription measures refractive error. To get a sense of how well you'll see with your prescription, it’s best to visit your eye care provider.

What is the best vision a person can possibly have?

The best recorded human vision is around 20/10, which is twice as sharp as 20/20. This means a person with 20/10 vision can see from 20 feet what someone with normal vision would see from only 10 feet away. Some birds, like eagles, are thought to have vision as sharp as 20/5.

What does experiencing 20/20 vision feel like?

Experiencing 20/20 vision means having clear, crisp vision at a distance of 20 feet. However, some people may still struggle with near tasks or have issues like color blindness, peripheral vision problems, or other visual limitations, even if they have 20/20 acuity.

Are there any daily activities that improve visual acuity?

While visual acuity generally doesn’t improve without corrective lenses or surgery, maintaining eye health through a balanced diet rich in vitamins (like Vitamin A), regular exercise, and minimizing eye strain can help preserve sharp vision. Specific exercises, such as focusing on objects at various distances, may help reduce eye fatigue, but these won’t correct refractive errors.

What vision is considered legally blind?

In the U.S., legal blindness is defined as having 20/200 vision or worse in the better eye with the best possible correction. This means that what a person with normal vision can see from 200 feet, someone with 20/200 vision would only be able to see from 20 feet.