Bats are blind
The old claim turned out to be wrong and was rejected by evidence.
TaughtBats cannot see at all. They navigate purely by echolocation, which is why we say "blind as a bat."
NowNo bat species is blind. All have functional eyes, many see well in low light, some see ultraviolet, and the large fruit bats rely on vision rather than echolocation.
What actually happened
Echolocation is real and remarkable, and it is what made bats famous. But it is a supplement to vision, not a replacement for it, and it is expensive to produce and only useful at short range.
Microbats use echolocation for hunting insects in the dark while also using vision for orientation, spotting landmarks, and detecting the horizon at dusk. Megabats, the large fruit bats, mostly do not echolocate at all and find food by sight and smell, with eyes proportionally large and well adapted for dim conditions. Several species have been shown to detect ultraviolet light, which humans cannot. The phrase "blind as a bat" is a good idiom and a bad zoology lesson.
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Who was taught this
Still standard through 2005, so anyone who finished school between 1950 and 1990 learned the earlier version.