Ever wonder what 20/20 eyesight really means? 20/20 vision is a phrase to describe a normal level of clarity of eyesight or visual acuity measured from 20 feet away from the object. That is to say that an individual with such vision can clearly see an object from 20 feet away that most people should be able to see from that distance.
For those who cannot see an object clearly at 20 feet away, the number is determined based on the distance at which they are able to see sharply, in comparison to the norm. For example, 20/100 vision indicates that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet away.
Someone with 20/200 visual acuity is considered legally blind however, they can often achieve much improved eyesight by using glasses or contacts or by undergoing LASIK if they are eligible.
A typical vision screening is done with the use of an eye chart usually the classic Snellen eye chart designed by Hermann Snellen, a Dutch eye doctor in the mid-1800's. While there are now many variations, the chart generally shows 11 lines of uppercase letters which get smaller in size as they move toward the bottom. The top of the chart usually shows the capital letter – ''E'' with letters being added gradually as you look down the chart. During the vision test, the optometrist will examine which is the line with the smallest lettering you can make out. Your score is determined since each row is given a rating, with the 20/20 row typically being assigned the eighth row. For young children, illiterate or disabled persons who are not able to read or vocalize letters, the ''Tumbling E'' chart is used. Similar to the traditional Snellen chart, this version portrays only the uppercase E in different directions. The eye doctor asks the patient to mimic which direction the ''fingers'' of the E are facing: right, left up or down. Both charts must be placed 20 feet away from the patient's eyes.
Even though 20/20 vision does indicate that the person's distance sight is average, this test alone does not indicate that the individual has flawless vision. Complete eyesight includes a number of other important skills such as peripheral vision, perception of depth, focus for near vision, color vision and coordination between the eyes to name a few.
While a vision screening with an eye chart will determine if you require a visual aid to see far away it doesn't give the optometrist a full perception of your total eye health. You should still book an annual comprehensive eye exam to screen for vision-threatening conditions. Call our office today to book a North Vancouver, BC eye test.