Ever ask what 20/20 vision truly means? The term 20/20 eyesight expresses a normal level of sharpness of eyesight (visual acuity) determined from 20 feet away from the object. That is to say that someone with 20/20 eyesight will be able to clearly see an object from 20 feet away that the majority of people should be able to see from such a distance.
In cases of individuals that don't have 20/20 visual acuity, the number is assigned based on where they begin to see clearly in relation to what is normally expected. For instance, 20/100 acuity indicates that you must be at a distance of 20 feet to see what someone with normal eyesight would see at 100 feet away.
An individual whose eyesight is 20/200 or worse is considered legally blind however, they can often achieve much improved eyesight by wearing prescription glasses or contacts or by having LASIK if they are eligible.
An average vision test is done with the use of an eye chart such as the familiar Snellen eye chart developed by Hermann Snellen, a Dutch eye doctor in the 1860's. While there are now many variations, the chart typically shows 11 lines of uppercase letters which get progressively smaller as one looks toward the bottom. The chart begins with one capital letter – ''E'' with the addition of more letters as they get smaller. During the vision test, the eye doctor will examine which is the line with the smallest lettering you can see clearly. Every row is assigned a distance, with the 20/20 line usually being ascribed the eighth row. In instances where the patient can't read, such as small children or disabled persons, a varied version of the chart is used called the ''Tumbling E''. At the same scale as the traditional Snellen chart, the ''Tumbling E'' is composed of only the uppercase letter E in different spatial orientations. The eye doctor asks the patient to point to the right, left, top or bottom according to the direction the E is facing. In order for the results to be accurate the chart needs to be placed at a distance of 20 feet from the patient's eyes.
Although 20/20 vision does show that the person sees at the norm from a distance this test on its own does not mean that the individual has flawless vision. There are many other necessary elements that contribute to your overall vision such as peripheral vision, perception of depth, focus for near vision, color vision and eye coordination to name a few.
While a vision screening using a Snellen chart can conclude whether you need eyeglasses to improve distance vision it doesn't give the optometrist a full understanding of your overall eye health. You should still book an annual comprehensive eye exam which can diagnose potential diseases. Contact our office today to schedule an eye exam in Kennesaw, GA.