When are Screen.width and Screen.height updated after changing the Screen.orientation value?

I'm testing on an iPad mini. When I change the logical orientation Screen.orientation=MyNewOrientation, Screen.width and Screen.height are not immediately reversed. Next frame they have a new value. If this is an asynchronous process, is there a way to be notified when Screen.width and Screen.height are updated?

Note : I'm asking this because I'm seeing a very short transition screen that is not very clean when switching the orientation on ipad mini and I suspect this has something to do with the question I'm asking here. I don't see this transition image when testing on Android.