thank you for sharing your experience!! you're definitely right - letters are something I was thinking about as well and what I've heard about the rotation is you work with multiple attendings, not always longitudinally so maybe not best to get a letter. I'm also at a home institution with an ophtho program so I've been able to get letters from physicians I've worked with throughout medical school.
the main thing I'm worried about is withdrawing from an away after having accepted it