What are the numbers on the eye chart?
When viewed at this distance, the bottom number of the Snellen fraction corresponds to a line of text on the eye chart. The large letter “E” on top on most charts corresponds to 20/200 visual acuity, and each subsequent line correlates to clearer visual acuity—20/20 being standardized as “normal” acuity.
What do numbers on vision test mean?
The smaller the second number gets, the better your eyesight, because it means you can see things from further away. So although 20 is average, 40 is worse, and 15 or 10 is better. If someone has 20/10 eyesight, they can be 20 feet away from something that everyone else has to see from only 10 feet away.
Is there a standard eye test chart?
The Snellen eye chart is the familiar, classic chart of big and little letters, known as “optotypes” in this case. The chart consists of 11 lines of block letters, beginning with a large single letter on the top row.
What do the numbers in 20 20 mean?
20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.
How do you read Snellen chart results?
Recording Snellen Results Top number equates to the distance (in metres) at which the test chart was presented (usually 6m), Bottom number identifies the position on the chart of the smallest line read by the ‘patient’. Eg; 6/60 means the subject can only see the top letter when viewed at 6m.
What is a good eye test score?
Perfect vision yields a score of 20/20, which means the viewer can see the same letters at 20 feet away what another normal viewer could also see at 20 feet. If your vision is less than perfect, you might receive a score of 20/40 or 20/50.
How big are the letters on an eye chart?
Snellen designed stylized letters on a 5×5 grid, which he called “optotypes.” He defined the reference standard (known today as “20/20”) as the ability to recognize one of his optotypes when it subtends an angle of 5 minutes of arc.