I received my Spanish driving licence renewal last week - well ahead of expiry (March 8th) date. Yesterday afternoon I took the health check (compulsory) at a Centro Medico-Psicotecnico (Note not your normal health centre) which consisted of an eye sight co-ordination test and a chat with a doctor. If your eyesight is OK and you are alive I think everybody will pass. The bad news is that it cost 34 euros (probably varies in other regions) You need to take a photo as they attach it to a certificate which must be submitted to Traffico as part of the renewal process.
For locations of these centres
Centros de Reconocimiento de Conductores
visit http://www.dgt.es