diecidecimi [20/20] in italian

Eyesight test with the Snellen chart, free, online, accurate

Warning, despite the proposed test, if properly calibrated, meets certain standards approved by the British Standards Inbstitution, can not in any way be a substitute for a medical test.
The letter size should be calculated based on distance, so as to form a precise angle between the eye and the letter. Since the pixel size varies from screen to screen, you need to calculate the precise size (in millimeters) of the pixels of your screen, so the program can offer you the letters in the right size.
For the calculation of dimensional letters and, as a source of this information I quote two pages of wikipedia: Visual_acuity and Snellen_chart . For proof, it is mentioned the size of a letter of 20/20 to 4.36mm, a distance of 3m. You can try it yourself to check the accuracy on your screen.
According to the British Standards Institution BS 4274-1:2003 only the letters C, D, E, F, H, K, N, P, R, U, V, and Z can be used to test visual acuity based on the readability of the letters.
In addition, the specification states that the luminance of the presentation should be uniform and not less than 120 cd/m2 and any variations across the test chart should not exceed 20% (for the value of your screen cd/m2 See specifications techniques, is normally present).

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Marescotti Matteo, a student of computer science at the University Amedeo Avogadro, passionate web design, programming.
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