You mean colloidal silver? Well it is used for extrernal infections and its also an antiseptic for medical tool so i think its completely safe to use.
I use both colloidal silver and added eyebright in an eye cup. Good stuff! I am using up the Dr. Christopher eyebright I have on hand but will be ordering the next one from Uny. Her formulas and those of Dr. Schulze are likely superior to the Dr. Christopher ones after his kids took over and the quality took a hit (or so it has been reported).
One caution, start with just a single drop or two of eyebright and work up to the maximum (4-5 drops). Cayenne is one of the main ingredients and it will most definitely burn, though you do get acclimated over time.