I never liked those sticky hydrometers. If you can get the eye drops on without stressing him out, the better. I know if I lift montys hide up, she will peek up at me, I'm sure long enough for me to get an eye drop in her eye. If the only way to get the eye drops in is to stress out the snake, and your vet said it was a good idea, I would go with your vets advice. But there should be a way to get the eye drops in without even touching the snake. They don't have eyelids that they can close on you. Best of luck!