Ever ask what 20/20 vision truly means? The phrase 20/20 eyesight describes normal visual acuity or sharpness of vision. In other words someone with 20/20 visual acuity will be able to see an object clearly from 20 feet away which is considered the norm to see from that distance.
In cases of individuals that don't have 20/20 vision, the number is assigned based on the distance at which they are able to see sharply, in comparison to the norm. As an example, if your vision is 20/100 that means that you must 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.
An individual whose vision is 20/200 or worse is considered legally blind however, they can often see normally by wearing glasses or contact lenses or by undergoing LASIK if they qualify.
A typical vision screening is done by using a vision chart most commonly the familiar Snellen eye chart created by Dutch eye doctor, Herman Snellen in the 1860's. While there are now a number of variations, the chart generally has 11 lines with uppercase letters which get progressively smaller as they move toward the bottom. The chart begins with one capital letter - ''E'' with letters being added gradually as you look down the chart. During the vision test, the eye doctor will assess the smallest line of letters you can see clearly. Each line is assigned a rating, with the 20/20 row typically being assigned forth from the bottom. In cases in which the patient can't read, such as small children or handicapped persons, the ''Tumbling E'' chart is employed. Similar to the traditional Snellen chart, this version portrays only the uppercase E in different directions. The optometrist tells the patient to point to the right, left, top or bottom to show which direction the E is facing. Both charts must be placed 20 feet away from where the patient is viewing it.
While 20/20 vision does show that an individual's distance vision is average, this test alone does not indicate that a person has flawless vision. There are a number of other essential abilities needed that contribute to your overall vision such as side or peripheral sight, perception of depth, color vision, near vision and focusing and eye coordination amongst others.
Although an eye exam with an eye chart can conclude if you need glasses for better distance vision it will not provide the optometrist a comprehensive understanding of your overall eye and vision health. You should still go in for a yearly comprehensive eye exam which can diagnose vision-threatening conditions. Contact us today to book a Lake Grove, NY eye test.