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I don't believe that the thick, white mucus has any connection to the optic nerve drusen. I think that this was a condensation of the Optive Refresh drop with your tears to produce that conglomerate.
There are so many different types of artificial tears on the market that they each have fairly distinct viscosities, colors, and sensations to meet the needs of different people. Some people need and like the thicker viscosity of the Optive Refresh, but then many people do not need or like it, which I imagine you don't.