Same as the UK CAA. Just go to the website and you'll get it.
Something like if its an initial medical, you must be more than +3 or -3 diopeters. Astigmatism must be between X and Y etc etc.
Check the UK CAA website. its pretty easy to find on google search.
This doesnt really answer the OPs question though so I suggest he/she clarifys with CX.