Interestingly enough, an older comment mentioned a study in the 1980s observed that people in submarines develop myopia: https://news.ycombinator.com/item?id=1

Interestingly enough, an older comment mentioned a study in the 1980s observed that people in submarines develop myopia: https://news.ycombinator.com/item?id=12064612 https://news.ycombinator.com/item?id=12064612 so adults (possibly young adults) do get it