Phosphate Buffered Saline (PBS) may cause lens calcification in a person with cataract, because lens calcium is likely to be elevated which risks formation of insoluble calcium phosphate.
Boric acid and borax also increase aggregation of lens proteins.
And to make sterile eye drops, we should not rely on a 'barefoot herbalist'. Only a reputable pharmaceutical company with experience of manufacturing eye drops, which still has a vestige of humanity left (do any such companies exist?), is acceptable.