The first true JAR renewal should involve a detailed eye test which includes the 'slit lamp' test. If your AME is a one man band it will be unlikely he will have the equipment for this test. I was referred to a local optician armed with a CAA form. Various eye tests carried out which the optician thought was 'over the top!'
The requirements now demand a lung function test. AME had a sort of instrument that you just huff into and it records the peak flow (not like the machine in the initial which nearly kills you!).
The other thing is a blood test to test for haemoglobin (which my AME thought was in his words 'a load of bollocks') and I think for the first one then 5 yearly a lipid profile (ie. cholesterol). My AME did not have the equipment for this so I had to go to local hospital. Many AME's will do a finger prick test.
Other than that, there is little difference. The form is a little more lengthy to fill in and the doc has to sit and fill out loads of boxes relating to validity of various bits and pieces ie. ECG and Audiogram etc.
This is just from memory. I doubt you will have much to worry about. Hope this helps.