Have you ever wondered why 20/20 is the standard for ''perfect'' vision and what it actually represents? 20/20 vision is a phrase used to describe 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 vision will be able to see an object clearly from 20 feet away that the majority of individuals are expected to be able to see from that distance.
For those who cannot see at 20/20, the number is designated based on the distance at which they are able to see clearly, in relation to the norm. As an example, 20/100 acuity means that at 20 feet you can only see what someone with normal vision can see from 100 feet away.
A person whose vision is 20/200 or below is considered legally blind but can often achieve much improved eyesight by using glasses or contact lenses or by having LASIK if they qualify.
An average eye exam is performed with the use of an eye chart usually the familiar Snellen eye chart developed by Dutch eye doctor, Herman Snellen in the mid-1800's. While today there are a number of variations, the chart usually has eleven lines with capital letters which get smaller in size as one looks downward. The chart begins with one capital letter - ''E'' with the addition of more letters as they get smaller. During the vision screening, the optometrist will look for the line with the smallest lettering you can read. Every row is given a rating, with the 20/20 line typically being assigned forth from the bottom. In cases in which the patient can't read, such as small children or disabled individuals, the ''Tumbling E'' chart is used. Similar to the regular Snellen chart, the ''Tumbling E'' shows only the uppercase E in different rotations. The optometrist asks the person being tested to indicate the direction the arms of the E are pointing: right, left top or bottom. In order for the results to be accurate the chart should be placed at a distance of 20 feet from the patient's eyes.
While 20/20 visual acuity does show that an individual is able to see as expected from a distance this test alone doesn't mean that the individual has perfect eyesight. Complete eyesight involves many other important skills such as peripheral vision, depth perception, focus for near vision, color vision and coordination between the eyes amongst others.
Although a vision screening using an eye chart can determine if you require a visual aid to see far away it will not give the optometrist a comprehensive understanding of your total eye and vision health. You should still schedule an annual comprehensive eye exam which can identify potential diseases. Call us now to schedule an eye exam in Glastonbury, CT.