Eboli without an eyepatch? Why?
The whole opera (the Schiller play, too) is remote from history in many ways: Philip was about 30 at this time, Carlos was mentally unstable to a critical degree, Rodrigo didn't exist, etc. So an eyepatch more or less won't make much difference, and by no means all productions include it -- in fact the previous Met production was probably one of the few at the time that did, as a sort of piquant extra.
[This message has been edited by Jon (edited 12-13-2010).]