Depends on the nature of your donorship. Some also give unused transplant items for medical research, you can gain an untold wealth of information about how we work by subjecting our components to different conditions, unfortunately usually doing so will result in the destruction of the device (outside a host, most organs won't survive very long).
Well... you won't be using it anymore, will you?
It may seem somewhat... distasteful... but understanding the problem is the first step towards solving it. I'm sure that no one really wants to let petty feelings of ownership hinder the helping of the species as a whole, do they?
Another possibility is that the donorship may be designed to be future-proof. While we can't transplant eyes today, it's likely that there's already someone's working on a procedure to allow this. Who knows, maybe tomorrow it will be possible...