Hi Simon... What you have written is correct, and it can be confusing...
Note the very first part of your info..."if you have never had a medical prescription" ...
As I said, nowadays, the Optician needs a "Prescription" from one's Medical Doctor... (these have a sell-by-date depending on one's age)
One's Medical Doctor can/does give a "Prescription" for a visit to the Optician for the normal Eyetest... or a visit to the Opthalmo....if he considers you need it...(and/.or this may also have been advised by the Optician when doing his Testing..)
If all this is prescribed by the Med Doc... CV+Mutuelle kick in.
If you visit the Opthalmo with a Medical Doctor's prescription...CV +Mutuelle pay. (and it may take months to get an appointment)
Once you are being "followed" by the Opthalmo.. you do not need a Medical Prescription for further visits to him. He will tell you how often he wants you to return for testing. (even so, visits need to be arranged months in advance.) It may be every few years, it may be never again... it might be every few months.. who knows.
The Opthalmo will check your current glasses and may Precribe a change (take the Opthalmo Prescription to the Optician) CV + Mutuelle)
If there is any discomfort with the Prescription issued by an Opthalmo, it should be reported back to him asap...(not just ignored) Though the Optician may confer with the Opthalmo to sort things out.
Whenever you feel eye-strain or similar... providing your Optician has a in-date Medical Prescription from your Doc.. he will give you the Eye Test and follow up..
CV+Mutuelle kick-in if there is a change in your sight.. or if it is 2 years or more since your last Test.
Should you have a serious sight problem .. your Medical Doctor will give a prescription for Emergency visit to the Opthalmo....usually dealt with through the Emergency section at the Hospitals..
It is complicated but also easy..