I'm assuming the RDA is way above the amount in cold lozenges containing zinc. I find that Coldeze is effective in diminishing the intensity of a cold, or even preventing a cold, if taken when symptoms are first noticed. Taking cold lozenges for several days would probably be fine. Most of the glaucoma community would like to see a well-designed study before putting our patients on ginkgo. Inflammation will increase the viscosity of the aqueous, making it harder for the eye's fluid to exit the globe.
Green tea is full of free radical scavengers, as well.
These are all recommended for macular degeneration, and since it is the ganglion cells of the retina that are damaged with the nerve axons in glaucoma, they should be beneficial. Green tea does have some caffeine in it, if you are sensitive to caffeine, but not as much as black tea. I eat a lot of romaine lettuce, but I never hear that mentioned as one of those green, leafy vegetables. The stronger the greens, the more effect. Kale is the best, but is pretty strong.