Disclaimer: This solution worked for Visual Studio 2013 with Qt 5.3
One of the reasons if your Qt program runs fine but the Visual Studio Intellisense does not detect Qt specific variables can be due to the necessary header files not being included. You will notice if you go to Project Properties->C/C++->Additional Include Directories, that there are several include entries defined with using QTDIR as an environment variable.
I’m sure you have figured out the solution now. You have to define this system variable to make Intellisense work. Add a new system variable called QTDIR, and point it to the QT installation with the version you are working with, ex: C:\Qt\5.3\msvc2012_opengl. This should solve your problem.
Note: There seems to be other problems that can cause Intellisense to not work with Qt, and they are pointed out in: http://qt-project.org/faq/answer/intellisense_does_not_work_for_my_qt_application._whats_wrong