In my opinion, Christina's position is very reasonable. It's simply not always practical to be afraid of everything, and one cannot do endless due diligence on everything. One comes to have a comfort level with some things based on information reasonably available - for example, we know BAK is bad today, just like those of us using contact lens solutions a couple of decades ago gradually came to know thimerasol was bad. So many of us may choose to avoid those and exercise reasonable caution with others. As a practical matter, many of us notice pretty soon if a preservative in a drop we use frequently is bothering us, and as I said we can't spend our lives worrying about the long-term effects of everything
Incidentally, the studies on polexitonium (polyquaternium-42) showed it to be no more toxic/irritating than saline even with frequent use at concentrations far higher than that used in Dr. Holly's drops. If I had the money to do a rigorous long-term study I'd do it, but I don't. My comfort level with this preservative stems partly from the study but also from the simple fact that I know so many people with severe ocular surface disease who have used it daily for ten years or more and tolerate it just as well now as when they started. That may not be scientific, but it works for me.
Incidentally, the studies on polexitonium (polyquaternium-42) showed it to be no more toxic/irritating than saline even with frequent use at concentrations far higher than that used in Dr. Holly's drops. If I had the money to do a rigorous long-term study I'd do it, but I don't. My comfort level with this preservative stems partly from the study but also from the simple fact that I know so many people with severe ocular surface disease who have used it daily for ten years or more and tolerate it just as well now as when they started. That may not be scientific, but it works for me.
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