Ever question what 20/20 vision really represents? 20/20 vision is a phrase to express a normal level of sharpness of eyesight also known as visual acuity determined from a 20 feet distance. That is to say that an individual with 20/20 eyesight can see an object clearly at a distance of 20 feet that the majority of people are expected to be able to see from such a distance.
In cases of individuals that cannot see an object clearly at 20 feet away, the number is designated based on where they begin to see clearly in comparison to the norm. For instance, if your acuity is 20/100 that means that you must be as close as 20 feet to see what a person with normal visual acuity can see at a distance of 100 feet.
One can also have vision that is better than the norm. For instance someone with 20/10 eyesight can see clearly at 20 feet an object that most can see only at 10 feet. Members of the animal kingdom particularly birds of prey have been known to have incredibly acute vision compared to man. For example, hawks have been known to have 20/2 eyesight, enabling them to spot prey from high in the air.
Most eye care professionals use a form of the Snellen eye chart, developed by Dutch eye doctor, Herman Snellen in the mid-1800's, to conduct an eye screening. While today there are many versions, the chart generally shows eleven rows with uppercase letters which get smaller in size as one looks toward the bottom. The top of the chart usually shows the capital letter – ''E'' and subsequently includes more letters on the lines as they get smaller. During the eye exam, the eye doctor will look for the line with the smallest lettering you can make out. Your score is determined since each row is given a distance, with the 20/20 line usually being assigned forth from the bottom. In instances in which the patient can't read, such as young children or handicapped individuals, the ''Tumbling E'' chart is employed. Similar to the regular Snellen chart, this version is composed of only the uppercase letter E in different directions. The optometrist asks the patient to indicate which direction the arms of the E are pointing.. Either chart must be placed at a distance of 20 feet from where the patient is viewing it.
While 20/20 eyesight does show that the person's distance vision is normal, this test alone does not mean that someone has flawless vision. ''Perfect'' vision includes a number of other necessary skills such as side or peripheral vision, perception of depth, focus for near vision, color vision and eye coordination amongst others.
While an eye exam using an eye chart will often conclude if you require a visual aid to see clearly at a distance it doesn't provide the optometrist a full picture of your overall eye health. You should still schedule an annual comprehensive eye exam which can identify any more serious conditions. Call us now to schedule a Long Beach, CA eye test.