What Is 20/20 Vision and Do I Need It?

Short answer: 20/20 vision means you can see at 20 feet what a person with normal vision sees at 20 feet. It is not perfect vision — it is average or normal vision. Most LASIK patients achieve 20/20 or better. Whether you need it depends on your lifestyle and activities, but for most vision correction surgery candidates, 20/20 or 20/16 is a realistic and desirable target.

The Eye Health and Vision Care hub covers visual acuity throughout its resources on prescriptions and exam outcomes. Here is the complete explanation.

How the Snellen Chart Works

The Snellen chart is the standard clinical tool for measuring visual acuity — the sharpness of your vision at a standardized distance. It was developed by Dutch ophthalmologist Herman Snellen in 1862 and remains the reference standard.

The fraction notation (20/20, 20/40, 20/200) means:

Numerator (top number): The distance in feet at which you are tested (20 feet, standardized)
Denominator (bottom number): The distance at which a person with normal vision would see the same letter

So:

20/20: You see at 20 feet what a normal eye sees at 20 feet. This is the reference standard for “normal” vision.
20/40: You need to be at 20 feet to see what a normal eye sees at 40 feet. Your vision is reduced.
20/200: You need to be at 20 feet to see what a normal eye sees at 200 feet. This is the legal definition of blindness (even with correction).
20/15 or 20/10: You can see at 20 feet what a normal eye would need to be at 15 or 10 feet to see. Better than average.

Is 20/20 the Best Possible Vision?

No. The Snellen chart only measures high-contrast distance acuity under standardized conditions. It does not capture:

Contrast sensitivity: The ability to distinguish objects against backgrounds of varying contrast (critical for driving at dusk, in fog, or in low-light conditions)
Night vision quality: Pupil size, optical aberrations, and tear film quality all affect real-world night vision
Depth perception: Depends on binocular vision function
Color discrimination
Peripheral vision

A patient can have 20/20 Snellen acuity and still have subjectively poor vision due to higher-order aberrations, poor contrast sensitivity, or glare. This is one reason that outcomes data for vision correction surgery now commonly includes not just Snellen acuity but also contrast sensitivity, patient satisfaction, and quality-of-life measures.

What Do LASIK Patients Typically Achieve?

In FDA clinical data for modern LASIK:

Approximately 92-98% of patients achieve 20/20 or better distance vision
A significant proportion achieve 20/16 or even 20/12 — better than the “normal” standard
Patients with higher pre-operative prescriptions may have somewhat lower rates of achieving 20/20, and higher rates of needing an enhancement

The goal of surgery is to match or exceed what you previously achieved with corrective lenses. If your best-corrected visual acuity (BCVA) before surgery was 20/25 due to amblyopia or other retinal limitations, surgery cannot improve on that biological ceiling — it can only match it.

What BCVA Means Before Surgery

Your best-corrected visual acuity — your vision with the best possible glasses correction — is the ceiling for what surgery can achieve. During a pre-surgical evaluation, the surgeon will measure your BCVA. If it is 20/15, you have the potential to see 20/15 after surgery. If it is 20/40 with the best correction, surgery cannot produce 20/20 — the limitation is biological, not optical.

This is why patients with amblyopia (where the brain suppresses one eye) should understand their BCVA expectation before surgery and set expectations accordingly. See understanding your eye prescription for how BCVA relates to your prescription numbers.

Do You Need 20/20?

For most daily activities, 20/40 uncorrected vision is the legal minimum for driving in most U.S. states without corrective lenses. Many surgeons aim for 20/20 or better as the primary outcome target because it provides comfortable function across all daily tasks without the variability of near-threshold acuity.

Pilots, certain military personnel, and other professionally licensed groups often have specific acuity requirements (20/20 or 20/16 uncorrected) that make achieving these targets clinically and professionally significant.