Althusser's important contribution here is that he sees ideology as an:

a)  An effect of the structure of our society

b) A force in which practices are interrelated, socio-consciousness is shaped.

So this stance is also known as structural Marxism. Althusser sees all these aspects of Marxism, in the sense of structure. When Althusser gives a structuralist explanation of ideology it may seem to many critics that it takes way the revolutionary element that we find in classical Marxism. For instance when he suggests that ideological forms like the educational system, the media, the judiciary etc. “interpellate” or hail out to individuals and place them in existing forms or moulds of subjectivity and identity, the revolutionary agency of subjects is not foregrounded.

Again as Durham and Kellner suggest:

“On this account, subjects were constructed as preconstituted individuals, men or women, members of a specific class, and were induced to identify with the roles, behavior, values, and practices of the existing state capitalist society…Combining psychoanalysis, Marxism, and structuralism, Althusser thus analyzed how individuals were incorporated into specific social systems and functioned to reproduce contemporary capitalist societies.”