Preservatives are necessary evils in the conventional multi dose eye droppers, as the ambient non-sterile as well as the left over drop exposed to ambience gains entry in the container from the same path as that of the drug flow path contaminating the liquid inside.
Preservatives are added, as mandated, to prevent the growth of microbial contaminants and biodegradation. Thus, preservatives have become a key component in ophthalmic formulations, common among them are:
Benzalkonium chloride (BAC/BAK),
Stabilized Oxychloro Complex (SOC)
Though preservatives help keep the containers sterile over the course of multiple uses, various studies have proved that preservatives induce ocular toxicity particularly in long term therapy, multiple applications, aged patients and in pre existing ocular surface diseases, such as :