Graham. laid this down on his screen :
What's the best way of locking them in that won't invalidate
your guarantee from the optician?
Why don't they do this for us?
If I don't tighten the screws on my varifocals on a
weekly basis the RH lens drops out!

A small dab of Locktite on the thread

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk