Health
Why eye charts use letters you can't easily guess
HERE’S THE INTERESTING PART
The giant chart you stare at during a checkup isn't just a random assortment of alphabet characters. Designed by Hermann Snellen in 1862, the grid specifically uses 'optotypes'—symbols meticulously crafted on a precise 5x5 grid. Some letters are entirely omitted because they are too easy to guess from blurry shapes, meaning the entire test is heavily rigged to challenge your visual acuity.
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