Developers often face the problem of maintaining read access to all documents for the database administrator, when users can edit Readers fields on the document or adjust the document's Readers property from a the Document Properties dialog. You can find the documents again by accessing the database locally from the server console, but that is a nuisance.
The best way to manage this is to put a hidden, computed when composed _Authors_ field on the form, with a formula such as "[Admin]".
All "authors" of a document have access to the document, but the presence of an Authors field doesn't restrict access for other users, as a Readers field would.
You could instead use a computed Readers field that uses @If to calculate "" or "[Admin]" depending whether there are other Readers listed on the form. However, this formula will not re-evaluate if a user adjusts read access while not in edit mode (e.g. using the Document Properties from a view).