Yogi: I can only keep my eyes open continuously for 20 minutes and then they get tired.

Sayadaw: We’re not opening our eyes for the whole hour – sometimes the eyes are open and sometimes they are closed.
Open-eye meditation means we are keeping them open naturally. For example, before you are sitting, what are you doing? You are keeping your eyes open naturally (most times open and naturally we blink regularly; also we don’t force our eyes to open wide and stare), right? Just do it like this when you meditate with your eyes open.