With regards to clause 4.2.3 Medical Device File, ISO 13485 did not state that the document preparer, reviewer and approver shall be a different person. However, in most practices, it is best that the preparer does not review and approve his or her own work so as to be objective. But the reviewer and the approver can be the same person.
If the same preparer&reviewer or same reviewer&approver is acceptable?
In this case, the same reviewer and approver are acceptable.