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Is 20/20 Vision “Perfect” Vision?

If you have an eye exam and are told you have 20/20 vision, does this mean you have per­fect eye­sight? Is it pos­si­ble to achieve even bet­ter than 20/20 vision? And what is “per­fect vision” any­way?

To answer these ques­tions, let’s take a clos­er look at vision-relat­ed ter­mi­nol­o­gy to ful­ly under­stand how eye doc­tors mea­sure the qual­i­ty of your vision.

Visual Acuity, Eyesight and Vision: What’s the Difference?

Visu­al acu­ity. This, lit­er­al­ly, is the sharp­ness of your vision. Visu­al acu­ity is mea­sured by your abil­i­ty to iden­ti­fy let­ters or num­bers on a stan­dard­ized eye chart from a spe­cif­ic view­ing dis­tance.

Visu­al acu­ity is a sta­t­ic mea­sure­ment, mean­ing you are sit­ting still dur­ing the test­ing and the let­ters or num­bers you are view­ing also are sta­tion­ary.

Visu­al acu­ity also is test­ed under high con­trast con­di­tions — typ­i­cal­ly, the let­ters or num­bers on the eye chart are black, and the back­ground of the chart is white.

Although visu­al acu­ity test­ing is very use­ful to deter­mine the rel­a­tive clar­i­ty of your eye­sight in stan­dard­ized con­di­tions, it isn’t pre­dic­tive of the qual­i­ty of your vision in all sit­u­a­tions. For exam­ple, it can’t pre­dict how well you would see:

  • Objects that are sim­i­lar in bright­ness to their back­ground
  • Col­ored objects
  • Mov­ing objects

Three major phys­i­cal and neu­ro­log­i­cal fac­tors deter­mine visu­al acu­ity:

  • How accu­rate­ly the cornea and lens of the eye focus light onto the reti­na
  • The sen­si­tiv­i­ty of the nerves in the reti­na and vision cen­ters in the brain
  • The abil­i­ty of the brain to inter­pret infor­ma­tion received from the eyes

Only light that is focused on a very small and high­ly sen­si­tive por­tion of the cen­tral reti­na (called the mac­u­la) influ­ences visu­al acu­ity mea­sure­ments obtained dur­ing an eye exam.

Eye­sight. The exact def­i­n­i­tion of “eye­sight” is dif­fi­cult to pin down. Depend­ing on which dic­tio­nary or oth­er resource you check, it can mean “abil­i­ty to see,” “the sense of see­ing,” “vision,” “range of sight” or “view.” Often, the terms “eye­sight” and “visu­al acu­ity” are used inter­change­ably.

Vision. This is a broad­er term than visu­al acu­ity or eye­sight. In addi­tion to sharp­ness of sight or sim­ply a descrip­tion of the abil­i­ty to see, the term “vision” usu­al­ly includes a wider range of visu­al abil­i­ties and skills. These include con­trast sen­si­tiv­i­ty, the abil­i­ty to track mov­ing objects with smooth and accu­rate eye move­ments, col­or vision, depth per­cep­tion, focus­ing speed and accu­ra­cy, and more.

If this more inclu­sive (and accu­rate) def­i­n­i­tion of “vision” is used, what most peo­ple call “20/20 vision” should real­ly be called “20/20 visu­al acu­ity.” Real­is­ti­cal­ly, that prob­a­bly won’t hap­pen. For bet­ter or worse, the term “20/20 vision” is like­ly here to stay.

What Is 20/20 Vision?

The term “20/20” and sim­i­lar frac­tions (such as 20/40, 20/60, etc.) are visu­al acu­ity mea­sure­ments. They also are called Snellen frac­tions, named after Her­man Snellen, the Dutch oph­thal­mol­o­gist who devel­oped this mea­sure­ment sys­tem in 1862.

In the Snellen visu­al acu­ity sys­tem, the top num­ber of the Snellen frac­tion is the view­ing dis­tance between the patient and the eye chart. In the Unit­ed States, this dis­tance typ­i­cal­ly is 20 feet; in oth­er coun­tries, it is 6 meters.

At this test­ing dis­tance, the size of the let­ters on one of the small­er lines near the bot­tom of the eye chart has been stan­dard­ized to cor­re­spond to “nor­mal” visu­al acu­ity — this is the “20/20” line. If you can iden­ti­fy the let­ters on this line but none small­er, you have nor­mal (20/20) visu­al acu­ity.

The increas­ing­ly larg­er let­ter sizes on the lines on the Snellen chart above the 20/20 line cor­re­spond to worse visu­al acu­ity mea­sure­ments (20/40, 20/60, etc.); the lines with small­er let­ters below the 20/20 line on the chart cor­re­spond to visu­al acu­ity mea­sure­ments that are even bet­ter than 20/20 vision (e.g., 20/15, 20/12, 20/10).

The sin­gle big “E” at the top of most Snellen eye charts cor­re­sponds to 20/200 visu­al acu­ity. If this is the small­est let­ter size you can dis­cern with your best cor­rec­tive lens­es in front of your eyes, you are legal­ly blind.

On most Snellen charts, the small­est let­ters cor­re­spond to 20/10 visu­al acu­ity. If you have 20/10 visu­al acu­ity, your eye­sight is twice as sharp as that of a per­son with nor­mal (20/20) vision.

Is It Possible to See Better Than 20/20?

Yes, it’s indeed pos­si­ble to have sharp­er than 20/20 vision. In fact, most peo­ple with young, healthy eyes are capa­ble of iden­ti­fy­ing at least some of the let­ters on the 20/15 line or even small­er let­ters on the Snellen chart.

This may be due in part to bet­ter print­ing meth­ods avail­able today vs. those in the 19th cen­tu­ry when Snellen was deter­min­ing the small­est let­ters a per­son with nor­mal vision should be able to dis­cern. So a case could be made that “nor­mal” visu­al acu­ity today is an abil­i­ty to iden­ti­fy let­ters that are a bit small­er than those on the 20/20 line of a tra­di­tion­al Snellen eye chart.

On the oth­er hand, peo­ple are liv­ing longer today than they did in Snellen’s era. Nor­mal aging changes in the eye, such as ear­ly cataracts, could jus­ti­fy con­sid­er­ing some­what larg­er let­ters than those on the 20/20 line as being indica­tive of “nor­mal” vision among adults in their 60s or old­er.

Regard­less of these con­sid­er­a­tions, let’s say your eye doc­tor says you have 20/20 vision (or, more accu­rate­ly, 20/20 visu­al acu­ity), and you want sharp­er eye­sight. What can you do?

If your 20/20 vision doesn’t seem sharp enough, it could be that your eyes have high­er-order aber­ra­tions (HOAs) that can­not be cor­rect­ed with reg­u­lar eye­glass­es or soft con­tact lens­es. Your eye doc­tor can check for these aber­ra­tions with wave­front tech­nol­o­gy that is avail­able in some eye care prac­tices.

If HOAs are caused by small irreg­u­lar­i­ties in the shape of the front sur­face of your eyes, being fit­ted with gas per­me­able con­tact lens­es (GP lens­es) often can improve your visu­al acu­ity bet­ter than eye­glass­es or soft con­tact lens­es. This is because GP lens­es are rigid and essen­tial­ly replace the eye’s irreg­u­lar front sur­face with a per­fect­ly smooth, curved sur­face to focus light more accu­rate­ly.

Anoth­er option might be cus­tom wave­front LASIK. This per­son­al­ized laser vision cor­rec­tion surgery can pro­vide vision that is com­pa­ra­ble to wear­ing rigid gas per­me­able con­tact lens­es (which often is sharp­er than the visu­al acu­ity pro­vid­ed by glass­es or soft con­tact lens­es), with­out the has­sle of the dai­ly con­tact lens care.

If you pre­fer to wear eye­glass­es to cor­rect your refrac­tive errors, glass­es with spe­cial high-def­i­n­i­tion lens­es might give you sharp­er vision than reg­u­lar eye­glass lens­es.

What Is “Perfect” Vision?

It’s near­ly impos­si­ble to quan­ti­fy what “per­fect” vision is. Besides, a more inter­est­ing ques­tion would be, “Per­fect for what?”

For exam­ple, if you are dri­ving on a sun­ny day, excel­lent Snellen visu­al acu­ity might be the main fac­tor in your sat­is­fac­tion with your vision. But your girl­friend, who has worse visu­al acu­ity than yours, might be hap­pi­er with her vision in the same cir­cum­stances because she is wear­ing polar­ized sun­glass­es with anti-reflec­tive coat­ing that enhance con­trast and block glare.

Or an ath­lete who has bet­ter than 20/20 vision might strug­gle with his per­for­mance because he doesn’t have cer­tain dynam­ic visu­al skills that allow him to react to mov­ing objects as quick­ly as a team­mate whose sta­t­ic visu­al acu­ity isn’t as sharp as his.

Where to Get Expert Advice

The first step to max­i­miz­ing the clar­i­ty and com­fort of your eye­sight in all sit­u­a­tions is to see a qual­i­fied optometrist or oph­thal­mol­o­gist for a com­pre­hen­sive eye exam and vision eval­u­a­tion.

If you are inter­est­ed in find­ing out if laser vision cor­rec­tion could sharp­en your vision bet­ter than glass­es or con­tacts, ask to be referred to an expe­ri­enced LASIK sur­geon for a con­sul­ta­tion.

If you want to max­i­mize your dynam­ic vision skills for sports and oth­er activ­i­ties, seek an eye doc­tor who is a sports vision spe­cial­ist and ask about sports vision train­ing.

Final­ly, if your child has 20/20 vision but is strug­gling with eye strain and oth­er vision prob­lems in school, seek the advice of an eye care provider who spe­cial­izes in children’s vision to have your child eval­u­at­ed for pos­si­ble learn­ing-relat­ed vision prob­lems.



September 5th, 2017|Comments Off on Is 20/20 Vision “Perfect” Vision?

About the Author:

Born in Connecticut and raised in Upstate New York , Dr. Stetson graduated Cum Laude from Colgate University in New York, and then earned an MD degree with honors at the University of Vermont College of Medicine. He distinguished himself again in residency at the Albany Medical Center, where he obtained the highest percentile in the Ophthalmology Knowledge Assessment Examinations. Dr. Stetson has performed more than 50,000 refractive surgeries and has been on staff at Diamond Vision since 2004, before becoming Medical Director in 2006.


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