Ever wonder why 20/20 is the standard for ''perfect'' vision and what it really stands for? The term 20/20 eyesight expresses a normal level of sharpness of vision also known as visual acuity assessed from 20 feet away from the object. That is to say that an individual with such visual acuity will be able to see an object clearly at a distance of 20 feet which is deemed normal to see clearly from that distance.
For those who don't have 20/20 visual acuity, their visual acuity score is designated according to where they begin to see clearly in relation to the norm. As an example, if your acuity is 20/100 that indicates that you have to be at a distance of 20 feet to see clearly what someone with normal vision would see at 100 feet away.
Someone whose vision is 20/200 or worse is considered blind, legally but can often see normally with the use of eyeglasses or contact lenses or by having LASIK if they qualify.
Most optometrists utilize a form of the Snellen eye chart, designed by Hermann Snellen, a Dutch eye doctor in the mid-1800's, to conduct an eye test. While today there are quite a few versions, the chart usually has 11 lines of uppercase letters which get smaller in size as one looks toward the bottom. The chart begins with the uppercase letter - ''E'' with letters being added gradually as you look down the chart. During the vision test, the eye doctor will look for the smallest line of letters you can see clearly. Every row is assigned a rating, with the 20/20 line usually being assigned the eighth row. In cases in which the patient can't read, such as small children or disabled persons, the ''Tumbling E'' chart is employed. Similar to the standard Snellen chart, this variation shows only the uppercase E in different spatial orientations. The patient uses their hand to mimic the direction the ''fingers'' of the E are pointing.. Both charts needs to be placed at a distance of 20 feet from the patient's eyes.
Even though 20/20 vision does indicate that the person's sight for distances is good, this test alone doesn't indicate that the individual has flawless eyesight. There are a number of other necessary elements that contribute to your overall vision such as side or peripheral sight, perception of depth, color vision, near vision and focusing and coordination between the eyes amongst others.
While an eye exam using an eye chart can conclude whether you require eyeglasses to see clearly at a distance it doesn't provide the optometrist a comprehensive picture of the total status of your eyes and vision. Make sure you still go in for a yearly comprehensive eye exam to screen for potential diseases. Contact us today to book a Fairfax, VA eye test.