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Snellen Chart

Tool to present Snellen Chart. The Snellen Chart is an an optometric test to determine visual acuity of a person in ophthalmology

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Snellen Chart -

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Snellen Chart

Snellen Chart

snellen.jpg

Answers to Questions (FAQ)

How to use the Snellen Chart

The chart is intended to be used at a distance of 20 feet (about 6 meters) but can be closer if reading difficulties are presented. The person tested must open one eye at a time. The examiner/the optician randomly select letters on each row and notes the right and wrong answers.

The score per eye is the result of the distance divided by the value of the smallest line read correctly. A visually healthy person can read the 20/20 row.

The result of the score enable to make a decision on whether or not to wear a visual correction device (glasses).

How the Snellen Chart was created?

The Snellen scale uses different letters depending on the country, the principle is that they are quite easily discernible.

In the original version, the letters were

A,C,E,G,L,N,P,R,T,5,V,Z,B,D,4,F,H,K,O,S,3,U,Y,A,C,E,G,L,2

But can be different and suitable for any type of audience.

Example: C,D,E,F,L,O,P,T,Z in the above image

The size of the letters decreases on each row which makes it possible to evaluate with a fraction or a decimal number the most value read by a person tested.

What are Snellen chart's dimensions?

The table should be printed so that the first letter E is 88mm high.

When the Monoyer Chart was created?

Snellen created it in 1862.

Source code

dCode retains ownership of the online 'Snellen Chart' tool source code. Except explicit open source licence (indicated CC / Creative Commons / free), any 'Snellen Chart' algorithm, applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or any 'Snellen Chart' function (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) and no data download, script, copy-paste, or API access for 'Snellen Chart' will be for free, same for offline use on PC, tablet, iPhone or Android ! dCode is free and online.

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Questions / Comments

Thanks to your feedback and relevant comments, dCode has developed the best 'Snellen Chart' tool, so feel free to write! Thank you!


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