If you're doing an Ophthalmology away rotation as a non-Ophthalmology applicant you may want to contact them early and let them know that. Do you want to be in the OR a few days a week? Because they're going to be trying to schedule you OR time with some sub-specialists most likely. If you're trying to do a rotation so that you can actually learn to see the retina, manage some primary care level eye problems appropriately, and know more to be more comfortable when a patient has an eye complaint - then I saw absolutely go for it. You could probably arrange a comparatively relaxed rotation and get some experience in those areas. But the standard way that an Ophthalmology away rotation is set up is not 'relaxed.' It's shuffling you around into various clinics, seeing how you perform with residents, trying to fit you in a presentation somewhere, and getting you OR time with attendings when possible. It's not what everyone has told you Ophthalmology is like and you won't be getting home early if you're doing the rotation like we do it.
All that to say if you're looking for a mixture of useful and relaxing you're going to have to personally set this up with any program. Most places would love to see more M4s that are heading into other fields learn more eye pathology and I'm sure they'd love to teach you as much as they can and let you out early. They just need to know what you're looking for ahead of time.