Printable eye chart

Exactly the distance the chart is made for — it is printed at the foot of every page. A standard chart in the US is read from 20 feet and in much of Europe from 6 metres; 10 ft and 3 m charts are the same chart scaled to half size for a smaller room. This page sizes the letters for the distance you pick, so measure from your eyes to the paper and stand there.

That at 20 feet you can read letters that a person with standard vision can read at 20 feet. 20/40 means reading at 20 feet what standard vision reads at 40, so the letters must be twice as large. 6/6 and 6/12 are the same measures with the distance in metres. A 20/20 letter subtends 5 minutes of arc, with strokes and gaps of 1 minute.

8.87 mm tall when the chart is read from 20 ft (6.096 m), 8.73 mm at 6 m and 4.43 mm at 10 ft: the height that subtends 5 minutes of arc, 2 × distance × tan(2.5′). Each row up is 10^0.1, about 1.26 times, larger; the 20/200 row is ten times the 20/20 one.

The logarithm of the minimum angle of resolution in minutes of arc: 0.0 is 20/20 (6/6), 0.3 is 20/40, 1.0 is 20/200, and negative values are better than 20/20. Charts built on it (Bailey–Lovie, ETDRS) step by 0.1 from row to row, put the same number of letters on each row where they fit, space letters one letter-width apart and rows one row-height of the next row apart, so every row is an equally hard task. This chart follows those rules, with fewer optotypes on the top rows when the paper is too narrow for five.

Sloan letters (C D H K N O R S V Z) are the letters of the ETDRS charts and the most familiar. The tumbling E and the Landolt C need no reading: the person points the way the E opens or the C’s gap faces, which suits young children and anyone who does not read Latin letters. The Landolt C is the reference optotype of ISO 8596. All three are drawn on the same 5 × 5 grid, so a row means the same acuity whichever you choose.

You can practise, screen and track changes, as long as the chart printed at true size, is well lit and you stand at the right distance. It is not a diagnosis: an eye examination checks far more than how small you can read, including eye health. If your vision has changed, see an optometrist or ophthalmologist, and see one urgently for sudden changes, pain, flashes or a curtain over your sight.

Because a printer set to Fit to page shrinks every letter by a few percent, which nobody can see by eye, and every row then tests sharper vision than its label says. The page carries a box the size of a bank card (85.60 × 53.98 mm, ISO/IEC 7810) and a line that must measure 100 mm or 4 inches. If either is off, print again at Actual size / 100%.

Choose the 10 ft or 3 m chart, or enter your own distance from 2 to 8 m: the letters are worked out for that distance, so the labels still mean 20/20, 20/40 and so on. A mirror doubles the distance, but it reverses the chart: letters read backwards and an E or C pointing left appears to point right.