The Snellen eye chart was originally introduced in 1862 by Herman Snellen. The Snellen eye test uses the idea of a subtended 5 minutes of arc with a 20 foot distance.  Non-reflecting, matte finish.

$17.75

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Description

Non-reflecting, matte finish.

The Snellen eye chart was originally introduced in 1862 by Herman Snellen. The Snellen eye test uses the idea of a subtended 5 minutes of arc with a 20 foot distance. This became the standard vision measurement. Also, Snellen developed the idea of a 5×5 grid for a standard for his optotypes. Each optotype must meet certain percentage requirements in this grid before it is used for testing. This helps to make a uniform and equal vision chart. The Snellen eye chart is the basis for many other vision tests.