Although we don't know what the ingredients of the eye salve were, here are some recipes for eye remedies from Dr. Chase, a contemporary of Dr. Fenner.
Oh, you don't want to put lead in your eye? O.K., let's try something else.
Yeah, opium, that's it!
Here's the front page from Dr. Chase's book, in case you want to look for your own copy or sue him for causing you to go blind.