Answer 1

Retrospective simple means to look back. Retrospective diagnosis (retro-diagnosis or paleo-diagnosis or posthumous diagnosis) is the process of identifying an ancient illness with the modern name of illness using modern concepts.
Example: Adolf Hitler was diagnosed to have Parkinsonism after a retrospective study of 300 hr of film of Hitler, from 1919 to 1940.

The term is also used to denote the analysis of specimen for the diagnosis of illness of past that is already resolved or the illness of dead.

Answer 2

A retrospective diagnosis ,also known as retrodiagnosis or posthumous diagnosis, is the practice of identifying an illness in a historical figure.it can be identify using modern knowledge, methods and disease classifications. Alternatively, it can be the more general attempt to give a modern name to an ancient and ill-defined scourge or plague.