Described in an ancient Arabic book, The Book of Fixed Stars, written by al-Sufi, an early astronomer is what has been called "the ARAB eye test". This test was used in ancient Persia, over 1000 years ago to evaluate the vision of elite warriors, as well as by desert Bedouins to test their children's eyesight.

There is a double star, which is really 2 stars (Mizar and the fainter Alcor) separated by 12 minutes of arc, located in the handle of Ursa Major (the Big Dipper). One needs very sharp vision to discriminate that there is a second fainter star next to the brighter one. There is an Arabic saying that, "He can see Alcor but cannot see the full moon", describing a person who can see trivial details, but not the overall picture.

Recent testing has shown that the abilty to discriminate between the two stars is almost identical to the more modern measurement of 20/20 vision.