20/20 vision is normal vision. Most people with nearsightedness, farsightedness, or astigmatism have worse than 20/20 vision without glasses or contacts, but can achieve 20/20 vision with them. LASIK or PRK can produce vision better than 20/20.
Many people have heard the phrase “20/20 vision” but are unsure what this actually means. Twenty-twenty vision is a term opthalmologists and optometrists use to refer to “normal” vision. It is the level of vision most people have with their glasses or contacts on. Of course, most people who need glasses or contacts have much worse vision than 20/20 without the use of these aides.
When we say “20/20” we are actually giving two numbers, both of them measued in feet. The top number is the number of feet that a person being tested stands from a test object of a certain size and certain contrast. This is always set at 20 feet. When you sit in an examination chair in your eye doctor’s office, you are looking at letters that are optically 20 feet away. The bottom number is where a normal person would stand to see exactly as well as you see from the exam chair. If the results of your vision show the bottom number is bigger than the top number (say 20/60), then the normal person can stand further back than you to see as well as you do because the normal person has better vision than you.
For example, 20/40 vision is considered the benchmark for passing a driver’s test in most states, even though this actually isn’t perfect vision. With 20/40 vision, a driver’s test applicant would see at 20 feet what a normal person could see at 40 feet. In other words, the normal person could stand twice as far away and still see as well as the driver. It may sound scary, but this means that a person can still pass a driver’s test with vision half that of a normal person!!
If someone has 20/100 vision, the normal person could stand 100 feet away and still see what the driver sees at 20 feet. Clearly, this level of vision would be too poor to pass a driver’s test.
If a driver has 20/20 vision, on the other hand, then the driver being tested sees at 20 feet what a normal person sees at 20 feet since the driver has normal vision.
I am often asked if LASIK or PRK can help make people see better than 20/20 after surgery. The answer is that LASIK or PRK definitely can help people see better than 20/20! This level of vision is often called “supervision.” In fact, 20/15 vision, which is vision better than 20/20 is a common result of Customized Wavefront LASIK or Customized Wavefront PRK. Some of my patients have even achieved 20/10 vision, which is vision twice as good as normal people have.
In the FDA clinical trials for the VISX Custom Vue method for performing Customized Wavefront LASIK, 70% of cases achieved 20/15 vision, vision superior to 20/20. With 20/15 vision, a normal person would have to get closer to the object to see as well as the patient — the patient could see at 20 feet what the normal person saw at 15 feet as the patient would have better than normal vision. Since the time of this FDA study, Customized Wavefront LASIK and Customized Wavefront PRK technology actually have gotten even better.
See Also
American Academy of Ophthalmology
Website for the largest professional organization of ophthalmologists in the United States
American Optometric Association
Discussion of 20/20 vision by the largest professional organization of optometrists in the United States.
Food and Drug Administration (FDA)
The governmental body which tests and approves medical devices used in LASIK, PRK
Abbott Medical Optics
Parent Company of the VISX Custom Vue System for Customized Wavefront LASIK
California Department of Motor Vehicles (DMV)
The state agency in charge of setting the visual standards for passing a drivers test in California