I suppose this varies from person to person and I can only speak as a glass wearer with some… uhhh… 30-ish years of practice: your eyes can get tired. I have some days when I can’t stand the feeling of my glasses and have to take them off a lot. My experience is that contacts make me really tired, much more than glasses. It’s like my brain refuses to function if I see like a normal person. It’s all just anecdotal unless a medic confirms it though :)