How To Use Snellen Chart?

How is the Snellen test performed?

The Snellen test uses a chart of letters or symbols.

Viewed from 14 to 20 feet away, this chart helps determine how well you can see letters and shapes.

During the test, you’ll sit or stand a specific distance away from the chart and cover one eye.

You’ll read out loud the letters you see with your uncovered eye.

How do you read a Snellen eye chart?

To interpret your reading, think of the numbers in feet. For instance, someone with 20/60 vision can read at 20 feet away what a person with normal vision could read at 60 feet away. Modern optometric exam rooms are equipped with electronic eye reading charts, making it easier to produce accurate readings.

How do you take a vision?


  • Ensure good natural light or illumination on the chart.
  • Explain the procedure to the patient.
  • Wash and dry the occluder and pinhole.
  • Test each eye separately – the ‘bad’ eye first.
  • Position the patient, sitting or standing, at a distance of 6 metres from the chart.

How many letters can you miss on a Snellen chart?

For example, 20/20 is 1.0, 20/40 is 0.5, 20/80 is 0.25, 20/100 is 0.2, and so on. Even if you miss one or two letters on the smallest line you can read, you are still considered to have vision equal to that line.

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