Have you ever wondered what 20/20 vision truly represents? 20/20 vision is a term used to describe normal visual acuity or clarity of vision. That is to say that an individual with such visual acuity will be able to clearly see an object at a distance of 20 feet that most people are expected to be able to see from such a distance.
For those who cannot see an object clearly at 20/20, the number is determined according to the first point at which they are able to see sharply, in relation to what is normally expected. For example, if your vision is 20/100 that indicates that you have to be at a distance of 20 feet to see clearly what someone with normal vision can see at 100 feet away.
An individual who is assessed with 20/200 visual acuity is considered legally blind but can often achieve much improved eyesight by wearing glasses or contacts or by undergoing LASIK if they qualify.
Most eye care professionals employ a form of the Snellen eye chart, which was designed by Dutch eye doctor, Herman Snellen in the mid-1800's, to conduct a vision exam. While today there are many variations, the chart usually has 11 rows with uppercase letters which get progressively smaller as one looks toward the bottom. The chart begins with one capital letter – ''E'' with letters being added gradually as you move down the chart. During the vision screening, the eye doctor will examine which is the line with the smallest lettering you can see clearly. Every line is given a distance, with the 20/20 line typically being assigned the eighth row. In cases where the patient isn't able to read, such as small children or disabled persons, an alternate version of the chart is used called the ''Tumbling E''. At the same scale as the traditional Snellen chart, this variation shows only the capital letter E in different rotations. The eye doctor tells the patient to point to the right, left, top or bottom to show which direction the E is facing. In order for the results to be accurate the chart should be positioned at a distance of 20 feet from the patient's eyes.
Despite what many think, 20/20 eyesight doesn't show someone sees perfectly but only that they see adequately from a distance. Complete vision involves many other important abilities such as peripheral vision, perception of depth, color vision, near vision and focusing and eye coordination to name a few.
While an eye exam using a Snellen chart will often establish whether you need eyeglasses to improve distance vision it will not give the eye doctor a comprehensive picture of the complete status of your eyes and vision. It's recommended that you still go in for a yearly comprehensive eye exam to screen for vision-threatening diseases. Call us now to book an eye exam in Escondido, CA.