Ever ask why 20/20 is the benchmark for ''perfect'' eyesight and what it truly represents? The term 20/20 vision describes a normal level of clarity of vision (visual acuity) assessed at a distance of 20 feet. In other words someone with such eyesight can clearly see an object from 20 feet away that the majority of individuals are expected to be able to see from that distance.
For those who cannot see an object clearly at 20/20, the number is designated according to the distance at which they are able to see sharply, 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 what a person with normal visual acuity would be able to see at 100 feet away.
A person with 20/200 eyesight is considered legally blind but can often see normally with the use of prescription glasses or contact lenses or by having laser eye surgery if they qualify.
A typical vision exam is performed with the use of a vision chart usually the classic Snellen eye chart developed by Dutch eye doctor, Herman Snellen in the mid-1800's. While there are now quite a few versions, the chart typically has eleven lines of capital letters which get smaller in size as one looks toward the bottom. The chart begins with one uppercase letter – ''E'' and gradually adds more letters on the lines as they get smaller. During the vision test, the optometrist will determine which is the smallest line of letters you can read. Each row is assigned a distance, with the 20/20 row typically being ascribed the eighth row. In cases where the patient isn't able to read, such as small children or disabled persons, a variation of the chart is used called the ''Tumbling E''. Similar to the traditional Snellen chart, this variation is composed of only the capital E in different directions. The optometrist asks the patient to show the rotational direction the arms of the E are pointing: right, left top or bottom. In order for the results to be accurate the chart must be positioned at a distance of 20 feet from the patient's eyes.
Despite common conception, 20/20 visual acuity doesn't show someone has flawless eyesight but merely that their distance vision is normal. There are many other essential abilities needed that contribute to your overall vision such as peripheral sight, depth perception, focus for near vision, color vision and coordination between the eyes amongst others.
Although a vision screening with an eye chart can determine if you need glasses to see far away it doesn't give the optometrist a complete perception of your complete eye health. It's recommended that you still go in for an annual comprehensive eye exam which can identify any more serious diseases. Contact our office today to schedule an eye exam in Richmond, KY.