Have you ever wondered why 20/20 is the benchmark for ''perfect'' eyesight and what it truly represents? 20/20 vision is a term to express a normal level of clarity of vision (visual acuity) assessed from 20 feet away from the object. That is to say that someone with such visual acuity can see an object clearly from 20 feet away which is regarded as the norm to see from that distance.
For those who don't have 20/20 vision, the number is assigned according to where they begin to see clearly in relation to what is normally expected. For example, if your vision is 20/100 that indicates that at 20 feet you can only see an object that a person with normal vision can see at 100 feet .
An individual can also have better than 20/20 vision. For instance someone with 20/10 eyesight can see sharply at 20 feet an object that most can only see at 10 feet distance. Certain animals have more acute eyesight in comparison to man. For example, hawks have been known to have 20/2 eyesight, designed for spotting prey from high in the air.
Most eye care professionals employ some version of the Snellen eye chart, which was designed by Hermann Snellen, a Dutch eye doctor in the 1860's, to conduct a vision screening. While today there are a number of versions, the chart generally has 11 lines with uppercase letters which get progressively smaller as they move downward. The chart begins with one uppercase letter – ''E'' and gradually adds more letters as they get smaller. During the eye exam, the eye doctor will determine which is the smallest line of letters you can make out. Your score is determined since each line is given a rating, with the 20/20 line usually being ascribed forth from the bottom. In cases where the patient isn't able to read, such as small children or disabled individuals, the ''Tumbling E'' chart is used. At the same scale as the standard Snellen chart, the ''Tumbling E'' is composed of only the capital letter E in different rotations. The eye doctor asks the person being tested to show the rotational direction the ''fingers'' of the E are pointing.. Both charts must be placed at a distance of 20 feet from the patient's eyes.
Although 20/20 eyesight does show that an individual's sight for distances is normal, this measure alone does not show that a person has flawless eyesight. Complete vision includes a number of other important abilities such as side or peripheral vision, perception of depth, color vision, near vision and focusing and coordination between the eyes to name a few.
Although an eye exam using an eye chart will establish if you need glasses to improve distance vision it will not give the optometrist a comprehensive understanding of the overall health of your eyes and vision. Make sure you still go in for a yearly comprehensive eye exam which can identify any more serious diseases. Contact us today to schedule a Bronx, NY eye test.