As you know, preservatives are a mixed blessing. The Food and Drug Administration requires that multidose bottles of medications include a preservative to kill bacteria and fungi that may contaminate the fluid in the bottle; as a result, for several decades our medications have contained preservatives specifically designed to keep the medications sterile during patient use and the life cycle of the bottle. Unfortunately, while these preservatives are very effective against pathogens, they were not specifically designed to be friendly to the eye. They tend to consist of harsh chemicals that stop bacterial growth but also harm corneal and conjunctival epithelial cells. After chronic use of medications containing these preservatives, the deleterious effect on anterior segment epithelial cells leads to poor production and maintenance of the tear film, resulting in problems such as dry-eye syndrome. Read More