Its all well and good getting Carl Zeiss lenses in your glasses....... BUT the CAA will still TEST your eyes using their own lenses which may NOT be Carl Zeiss....
The be all and end all of the result you get will depend on THE CAA results and nobody else's.... So regardless of which optician you go to and what results you get... Changing optician to get a better result will only make the 'difference' larger if the CAA results are less....
You can however almost guarantee that the CAA WILL be using the BEST equipment available (they have to to justify our silly costs)
Hope this makes sense
JON