If one eye is seeing 20/200 or less, the other eye must be 20/40 or better to pass the eye test. People are considered as legally blind when their corrected vision in both eyes is 20/200 or less.

Eye doctor Herman Snellen (Dutch, 1834–1908) developed the most commonly used eye chart in the 1860s. The now iconic Snellen chart contains 11 rows of capital letters decreasing in size as the eye ...

At least once in your life, you must have squinted at the eye chart at the doctor’s office or DMV, trying to make out the blurry bottom line. Turns out, there’s some very precise math that ...