I thought I was a major 'toughie' so I tried five drops for starters - YOWEE (plus!).
I can handle one or two drops. I'd expect in my upcoming "heal my vision" months, I'll work up to over 5 fairly easily.
(If I hadn't known already how safe it really is, I would have NEVER used it again after that first time).
This really is a very effective product; I've used it one & off for a couple of years and I always have more clarity and tears/moisture, even after only one 'dose'.