If you know the dangers of mercury, it is hard to imaged
its use in anything eye related.
Knowing that mercury in the bloodstream will store in the brain makes it even more unimaginable.
Even more startling is that eye products can contain mercury as a preservative, even though mercury has been linked to poor eye health and cataracts. To make matters worse, the mercury used can have one of many names that allow it to be conveniently hidden. This system leaves the consumer to be their own advocate and that task can be daunting.
The FDA website, [Code of Federal Regulations], [Title 21, Volume 5], [Revised as of April 1, 2016], [CITE: 21CFR349.50]
makes the following statement that directs manufacturers on proper labelling:
(3) For ophthalmic drug products containing mercury compounds used as a preservative. "This product contains (name and quantity of mercury-containing ingredient) as a preservative. Do not use this product if you are sensitive to" (select one of the following: "mercury" or "(insert name of mercury-containing ingredient) or any other ingredient containing mercury)."
Reading the FDA statement carefully makes it clear that you can easily misinterpret any message of mercury content. You will not see legible red letters that state "This Product Contains Mercury." You will instead see the a name and quantity of the "mercury-containing" ingredient. The name of the mercury-containing ingredient may be completely foreign and in no way represent to you that you will be adding mercury to your eye.
When you see a message that says "Do not use this product if you are sensitive to mercury" regard this as a deceitful and misleading. No one is "sensitive" to mercury. Mercury is an extremely dangerous element that is second only to plutonium in toxicity to human and animal life. When a toxin will kill, it is hardly fair to ask if one might be "sensitive" to its attributes.
Unfortunately, there is no clear directive when it comes to deciphering the potential of mercury in products you use. Three familiar names for mercury in optic care include thimerosal, which has more than one spelling, PMA, also know as phenyl mercuric acetate and PMN, known as phenyl mercuric nitrate. All three are approved by the FDA for ophthalmologic use as a preservative and there are certainly others.
I wish I could make this easier, but there is intentionally, no easy answer. The FDA has an interactive site that will decode the names you will find on ingredient lists and they do offer telephone assistance. Neither is likely to be easy.