I read that scientists say that masturbation can cause blindness. is it true?

No : Masturbation is harmless, and is a normal behavior. It does not cause one to "go blind" or have hairy palms. No reputable scientist or doctor would say this, unless he or she just got out f a time machine from before 1900 ce.

Nope. : I think the scientific data in that area is lacking to support that theory.

No: Masturbation is a normal part of human sexuality.Some cultures frown on the process & develop such myths to suppress it. Most seldom discuss it openly. If anyone does so to the exclusion of interacting with people ; pursuing age ; peer related activities, it can interfere with normal emotional growth, as any preoccupation might. For most, it is simply part of their life.