Have you ever had an eye exam? If yes, you are likely familiar with the eye exam chart that your eye doctor asks you to read. In 1862, Dr. Herman Snellen designed the first eye exam chart to measure monocular and binocular vision. 
 

Monocular vision is when you see only through one eye, while binocular vision is when you see through both eyes. The Snellen chart is most probably what you will see at your eye doctor's office. But many eye exam charts are available, such as the tumbling E and Jaeger eye charts. 
 

Here is a brief look at them.
 

Snellen Eye Chart

A Snellen eye chart has 11 rows of big letters, with the first row starting with the capital letter E. The other rows have smaller letters. You read the letters from start to end and left to right while covering one eye and then the other.
 

Tumbling E Eye Chart

All the letters on a tumbling E eye chart are capital letters E rotated at 90-degree angles. Eye doctors use this chart for patients who cannot read. The eye doctor will ask you to lift three fingers and point in the direction of the letters.
 

Jaeger Eye Chart

The Jaeger eye chart tests near vision using a hand-held card with printed paragraphs of various text sizes. The text size increases from a height of 0.37 meters to 2.25 meters. You are to hold the card at a measured distance and read the paragraph you can see clearly from that distance. The Jaeger eye chart will determine if you are nearsighted and the degree of it.
 

So, how does using eye exam charts work?

Measuring Visual Acuity

An eye chart can measure how clear and sharp your vision is. Your ability to read letters on the chart will tell your eye doctor whether you need vision correction. It determines whether you need eyeglasses or contact lenses to help you see better or if you need to change your lens prescription.
 

The type of eye chart your eye doctor uses will rely on your individual needs and abilities. For instance, optometrists will use eye charts with patterns or pictures for younger patients. This is especially so if they have not learned how to read or identify numbers and letters.
 

Detecting Nearsightedness or Farsightedness

Eye charts can measure how well you see distances. Your eye doctor will have you look at an eye chart and read small lines of text from 20 feet away. If you read clearly at 20 feet (or six meters), you have 20/20 vision like most people.
 

Restrictions of Eye Exam Charts

Eye exam charts are accurate in monitoring visual acuity and testing vision impairment. But the charts do have some restrictions. They cannot detect eye diseases, diagnose retinal problems, or measure things like depth perception and side vision. But as crucial parts of any eye test, eye charts help eye doctors examine visual acuity and determine whether you need corrective eyewear.
 

For more on how an eye chart exam works, visit the Eye Center of Virginia at our office in Williamsburg, Virginia. Call (757) 919-3500 to book an appointment today.