After a lifetime of mercury toxicity, I can never be convinced there is any practical use for it in the eyes.
Castor Oil, kept sterile and administered with a sterile dropper, is the perfect solution for dry eye. It is soothing and absorbs rather quickly.
A positive side effect is that it can help to dissolve the cloudy lens of a cataract. If used on eyelashes and eyebrows it will stimulate new growth.
The biggest reason to replace commercial eyedrops with castor oil is that there are no chemical side effects.
Commercial eyedrops, as well as nose and ear drops, can contain mercury.