The Eye Test Chart - also known as the Snellen Chart - The Wimpole Eye Clinic (2024)

FAQs

What is the Snellen chart also known as? ›

It was developed by the Dutch ophthalmologist Herman Snellen in 1862 and was adopted by medical professionals in many countries who have used it for more than 100 years. Snellen chart. Also called: Snellen eye chart.

You stand 20 feet away from the Snellen chart, and read from it without your glasses or contacts. You cover one eye and read out the smallest line of letters you can see. Then you cover the other eye and do it again. In some offices, you view the chart through a mirror.

How is the Snellen Chart used to assess visual acuity? - Snellen chart is composed of a series of progressively smaller rows of letters; person is asked to read the lowest line possible. The fraction 20/20 is considered the standard of normal vision.

The top line on the chart is designated 6/60. The second line up from the bottom (on most charts) is 6/6 and represents 'normal' sight – commonly known as 20/20 vision, particularly in the USA, as 6 metres is equivalent to 20 feet.

The visual acuity test is used to determine the smallest letters you can read on a standardized chart (Snellen chart) or a card held 20 feet (6 meters) away. Special charts are used when testing at distances shorter than 20 feet (6 meters).

These days, optometrists and ophthalmologists use the Snellen eye chart as part of a more comprehensive eye exam. Other tests your doctor may use in coordination with the Snellen eye chart include: A refraction test — This test uses a device called a phoropter.

The most common in clinical practice is the Snellen chart, while research studies more often use logMAR charts, such as the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart. The Snellen Chart uses a geometric scale to measure visual acuity, with normal vision at a distance being set at 20/20.

A Snellen chart is an eye chart that can be used to measure visual acuity.

The Snellen letter eye test is a normal part of your routine eye appointment. Your optician will present the chart containing rows of letters of varying sizes, and ask you to read the letters aloud. They might also place lenses in front of your eyes to see if the chart becomes clearer for you.

To pass, the individual must correctly identify 3 out of 5 letters on their critical line, 20/40 in each eye.

How to do a snellen test at home? ›

In the United States we think of "normal" vision as being 20/20, although maximum human acuity is even finer at 20/16 to 20/12. Therefore, interestingly, "normal" acuity is not "perfect" vision. The common 20/20 vision standard can be considered the lower limit of normal or as a screening cutoff.

The Snellen eye chart: The Snellen visual acuity test is probably what you're picturing if you think of a vision test. It's a wall chart with rows of letters printed on it. The letters are big at the top, and each row gets increasingly smaller the farther down on the chart you look.

The Snellen chart is the most widely used. Alternative types of eye charts include the logMAR chart, Landolt C, E chart, Lea test, Golovin–Sivtsev table, the Rosenbaum chart, and the Jaeger chart.

The Snellen acuity = Test distance (feet)/Letter size read (Snellen equivalent). For example, if the patient could read the 160 line at 1 meter, a 5' equivalent, their acuity would be recorded as 5/160. 5/160 is equal to a Snellen acuity of 20/640.