Have you ever wondered what 20/20 eyesight actually means? 20/20 vision is a term used to express a normal level of sharpness of eyesight also known as visual acuity determined from 20 feet away from the object. In other words someone with 20/20 vision will be able to clearly see an object at a distance of 20 feet which is regarded as normal to see from that distance.
In cases of individuals that cannot see at 20 feet away, their visual acuity score is determined according to the first point at which they are able to see clearly, in comparison to what is normally expected. For instance, 20/100 vision means that you have to be as close as 20 feet to see clearly what a person with normal eyesight would be able to see at a distance of 100 feet.
It's also possible to have better than 20/20 vision. For example a person that has 20/10 vision can see sharply at 20 feet what most can only see at 10 feet distance. A number of animals have been known to have incredibly acute eyesight compared to what humans are capable of. A hawk for instance can have 20/2 vision, designed for spotting prey from great heights.
An average eye test is performed by using an eye chart such as the familiar Snellen eye chart invented by Hermann Snellen, a Dutch eye doctor in the mid-1800's. While there are many versions, the chart generally has eleven lines of capital letters which get smaller in size as they move toward the bottom. The chart begins with one capital letter – ''E'' and subsequently adds more letters on the lines as they get smaller. During the vision screening, the eye doctor will assess the line with the smallest lettering you can make out. Your score is determined since each row is assigned a rating, with the 20/20 row typically being assigned the eighth row. For young children, illiterate or disabled persons who are not able to read or vocalize letters, a different version of the chart is used called the ''Tumbling E''. Similar to the standard Snellen chart, this variation is composed of only the uppercase letter E in different rotations. The patient uses their hand to indicate which direction the arms of the E are facing.. Either chart should be positioned at a distance of 20 feet from where the patient is viewing it.
Even though 20/20 vision does indicate that an individual sees as expected from a distance this test alone does not suggest that someone has perfect eyesight. Complete eyesight involves a number of other important abilities such as side or peripheral vision, depth perception, focus for near vision, color vision and coordination between the eyes amongst others.
It's important to remember that even though an eye exam with a Snellen chart can conclude if you need glasses to see far away it doesn't provide the optometrist a full understanding of the complete health of your eyes and vision. You should still go in for a yearly comprehensive eye exam to screen for potential conditions. Contact our office today to book an eye exam in Myrtle Beach, SC.