What is the first thing you think of when you hear the phrase 20/20 vision? For many people, the words “best” or “perfect” come to mind. However, there is a common misconception about what 20/20 vision actually means and how it relates to what you see. This blog will expand on visual acuity and how refractive error treatments, such as LASIK surgery, can improve your vision.
What Does 20/20 Vision Mean?
Visual acuity describes how clearly you see objects at a given distance. Two numbers make up your visual acuity.
During an eye exam, your eye doctor will ask you to read letters from a chart. Typically, you will be positioned 20 feet away from the chart. This accounts for the top number of your visual acuity. If you are wondering why 20 feet is the standard distance, this is the distance at which your eye can relax and does not have to change focus to produce an image on the retina (the thin layer of tissue at the back of the eye).
The bottom number accounts for the distance in which someone with normal eyesight can read the same line. Therefore, 20/20 vision means you and a person with normal eyesight can both see objects clearly from 20 feet away. Simply put, 20/20 vision indicates you have normal, average vision.
People who have below average vision will have a higher bottom number. For example, 20/100 vision means you can see objects at 20 feet away that most people can see at 100 feet away. In other words, those objects would appear blurry to you at 100 feet and you would need to be 80 feet closer to see them clearly.
What Is Better than 20/20 Vision?
Many people view 20/20 vision as the ideal or the perfect vision, however, there are people who can see better than 20/20. Clearly reading the smallest line on an eye chart would indicate you have 20/10 vision, meaning your vision is sharper than average and you see objects from20 feet away that most people would need to be 10 feet closer to see.
It is important not to get too caught up in having “perfect” vision. According to the American Academy of Ophthalmology, only about 35% of adults have 20/20 vision without corrective lenses such as glasses or contacts. Even with correction for refractive error, only about 75% of adults experience 20/20 vision.
How to Check Visual Acuity
An eye chart test is the most common way to test visual acuity. While this test may be performed in a primary care physician’s office or at school or work, it is best to have your vision checked as part of a comprehensive eye exam by a licensed optometrist or ophthalmologist.
Eye Test Chart
The Snellen eye chart is the most common eye chart used to test for visual acuity. The chart was created by Dutch ophthalmologist Hermann Snellen in 1862. More than 170 years later, it is still used by nearly every optometrist and ophthalmologist.
The chart consists of 11 lines that feature bold, black letters – C, D, E, F, L, O, P, T, and Z. The first line is one letter – usually E – and the bottom line is nine letters. From top to bottom, each row has an increase in letters but these letters decrease in size.
Whichever letter (or letters) you can read from 20 feet away determines your visual acuity. For example, if you cover one eye and you can only see the top line with a single “E” then you would have 20/200 vision. This would signal to your eye doctor that you have a significant refractive error.
Refractive Error Treatment
People with refractive errors have non-surgical and surgical options to correct their vision.
Non-surgical treatments
Glasses: Many people opt for glasses to correct their vision. Prescription eyeglasses bend light so it can focus on the retina to produce a clearer image. Depending on the results of your visual acuity test, you may either need reading glasses, single vision lenses, or multifocal lenses.
Contacts: These thin lenses sit on the top of the cornea to improve vision clarity. Contacts come in a variety of types – they can either be soft or hard; for daily use or extended wear (worn overnight); or for single use or reusable wear. As contact lenses have advanced, they can now treat nearsightedness, farsightedness, astigmatism, and presbyopia. About 45 million Americans wear contacts, according to the National Eye Institute.
Surgical treatments
LASIK: This is a type of refractive surgery that can correct nearsightedness, farsightedness, and astigmatism. In a normal eye, the cornea (the clear, outer layer of the eye) bends light and positions it to land on the retina. From there, the retina sends images to your brain to signal what you see. In people with refractive errors, distortions to the retina cause vision problems. LASIK surgery involves using a laser to reshape the cornea to allow light to pass through for clearer vision.
Does LASIK Give you 20/20 Vision?
More than 99% of people who receive LASIK achieve better than 20/40 vision and more than 90% achieve 20/20 or better, according to the American Refractive Surgery Council. Your vision will improve to 20/20 – or close to it – a few days after your LASIK procedure. While the changes are immediate, you may eventually need glasses for driving at night or reading as you age. This is due to your eye’s inability to focus on objects the older you get.
There are several factors that can influence your chance of achieving 20/20 vision following LASIK, including the following:
Your existing prescription: People with a severe refractive error for nearsightedness are less likely to achieve 20/20 vision following LASIK.
Your eye anatomy: People with a stretched or thin cornea may not be able to achieve 20/20 vision. Preexisting conditions such as dry eye syndrome or enlarged pupils may also affect the outcome.
Preexisting eye conditions: People with glaucoma, cataracts, or other eye diseases generally aren’t good candidates for LASIK.
Your surgeon: Choosing a reputable and experienced surgeon to perform the surgery, such as the ones at the Dean McGee Eye Institute, can positively affect the visual acuity you experience following LASIK.
