Probably sense I was a child as I unintentionally did it for as long as I can remember (bc autism I guess)and only real difference is a very slight difference in prescription in glasses for each eye but genetics make my eyes bad so honestly don’t know. The contrast difference is only noticeable at low light levels as one sees better in the dark which is weird.

I have contrast and vision differences between eyes. Probably because for a long time at night when I get up in the middle of the night I keep one eye from navigating the dark and when light turns in I switch. So I guess doing this for years made the contrast of each eye can detect different.