Eye Health

The Chemistry of Eye Care Products

I recently ran into a patient at a Crossroads art gallery who I had not seen since last Spring. During our conversation, she mentioned using an over-the-counter eye drop to help with discomfort. After trying Optive, an eye lubricating drop that I happened to have a sample of in my car, she immediately felt an improvement. As is often the case with patients, she asked what the difference was between it and other eye lubricating drops.

Many generic eye lubricating drops, eye allergy drops, contact lens re-wetting drops, and contact lens solutions are available over the counter, most of which I do not recommend. The basic problem is that all must use chemicals to kill micro-organisms, such as bacteria, but it is the chemical used that determines how well a patient tolerates a particular product. Generic products tend to be preserved with thimerosol or chlorohexadine which are common and needed additives to many eye medications. The difference is that eye medications tend to be used for short periods of time, but if these same chemicals are present in products used daily, sensitivity or an allergic reaction may become an added problem. Benzalkonium chloride (also listed as BAK) is another common ingredient and may produce eye dryness; an interesting side effect for a frequently used eye lubricating drop. Adding to the confusion is that derivatives of these same chemicals have names that are completely different and that generic solutions may suddenly change ingredients without changing names; this is why a generic product that was comfortable in the past may suddenly become uncomfortable. The eye lubricating drops that I most often recommend, Optive and Systane, do not use these chemicals and that was why my patient immediately felt an improvement after using Optive.

About a week before this incident, I ran into a patient at Scott Fitness who asked about a contact lens solution that he had doubts about using. After purchasing contact lenses outside of our office, they were shipped to his home along with four bottles of a contact lens solution that he had not authorized to purchase. His contact lenses were made with the newest polymer available, silicone hydrogel, which meant that besides avoiding the above chemicals, his contact lenses were incompatible with a different class of chemicals called biguinides. He later showed me a bottle of the solution and I was surprised to find that it contained both polyhexamethylene biguinide and thimerosol. I recommended that he ask for a refund from the supplier and that he file a complaint with the Federal Trade Commission for the unauthorized charges and for being provided an incompatible product with his contact lenses.

So how does your contact lens solution compare to others?

My point in all of this is that once a patient leaves our office, we have no idea as to what they may be putting into their eyes. Several times a year, I evaluate a patient for eye redness and irritation only to discover that a generic product containing the above chemicals is causing the problem. If you are uncertain about a generic eye care product, please look over the ingredients carefully or send us an email if you have any questions.