Sfomarc.
You will find each and every ICAO requirement within the ICAO bookset or its annexes. Sorry I don't know which one is germane to medicals but I imagine a trawl through their website will find it. Bear in mind that ICAO requirements form the minimum standard in all areas and that most advanced aviation states have stricter criteria.
I can't see there being any difference for pilots aged over 60. We either meet the standard or we don't.
Confundemus