Hi,
Eyesight test at renewal involves reading the chart with corrected and uncorrected vision. You must have 6/9 in each eye, and 6/6 binocular vision. You must show a recent eyesight prescription to your AME. The AME will also have a quick check on the condition of your eyes.
Then every 5 years, you must undergo a full eyesight test with an approved optician. Similar to the initial eyesight test I would think (I doubt anyone has had this done yet). The date of your next full eyesight test should be shown on the bottom of of your JAA Class 1 Certificate.
Hope this helps
Barney