If you have been to an eye clinic and told that your vision is 20/20, does it mean that your eyesight is perfect? Or have you ever discussed with your ophthalmologist if you can achieve better eyesight than 20/20 vision?
To acquire a better understanding of vision-related terminologies, let us have a closer look at how an ophthalmologist measures your visual acuity.
What is Visual Acuity?
The term visual acuity refers to your vision quality or vision sharpness. Your eye doctor or ophthalmologist measures it by assessing your ability to recognize numbers or letters on a standardized chart. The most important part of the process is the ‘viewing distance’ that determines the quality of your vision. Here comes the terms 20/20 or 20/40 into the picture.
During visual acuity test, you have to sit still at a specific distance (20 feet) to identify stationary numbers or letters. That is called static measurement. Typically, an eye doctor conducts the test in contrast conditions in which numbers and letters on the viewing chart are in black font with a white background.
The visual acuity test determines your ability to see, but it does not predict your vision quality in different situations. For instance, it cannot predict how clear you can see, such as,
- Moving objects
- Objects with similar brightness in the background
- Colored objects
Vision Acuity Testing
Since you know what term visual acuity refers to, let us see how it is measured.
The terms ‘20/20 or 20/40’ are acuity measurements. The fractions are significant in terms of determining the sharpness of your eyesight. Developed by Dutch ophthalmologist Herman Shellen in 1862, these acuity measurements are called Shellen fractions.
The acuity system has a specific testing distance of 20 feet. At this distance, the number and letters size on the bottom line of eye chart are standard up to 20/20 line, which is a normal acuity measurement. If a patient identifies the numbers and letters from this distance, he/she has a normal visual acuity of 20/20.
On the other hand, if the patient faces difficulty in identifying the letters on the lines of Shellen chart, the ophthalmologist increases the letter size from the 20/20 line to 20/40, 20/60, and so on. It corresponds to poor eyesight or visual acuity. However, if the patient can identify the smaller letters and numbers below 20/20 line on Shellen chart, they have better visual acuity.
There is no denying that you can have sharper and better visual acuity than 20/20. Young people with healthy eyes can identify letters below 20/15 on the eye chart. You can consult your eye doctor if your normal 20/20 vision is not sharp enough for you.
Overall, if you have 20/20 visual acuity, it means you have perfect eyesight. Consulting your eye doctor is the right way to take professional guidance to improve your visual acuity.