Ophthalmic products come in a variety of package formats and have a variety of eye-care applications. The liquid filled package formats are often soft containers with snap on or torque screw caps, but also include foil lidded blister packs for single use contacts. Most contact lens solutions clean, disinfect, lubricate, and remove protein deposits from the lens while matching certain chemical properties of the ocular area. While these solutions may disinfect, similar properties to ocular fluids and increasing resilience of new bacterial and fungal strains make contamination a greater concern. Any breach, channel, or micro leak in the container closure greatly increases the risk of contamination of the ophthalmic solution.
The primary culprit to contaminated eye care solution is package defects. The soft plastic containers and snap caps are typically blow molded plastics. The area for primary concern with both torque and snap on caps is the flange area of the bottle. While visual inspection and leak testing may detect many container failure modes of an uncapped container, slight inaccuracies or marks in the flange area provide a clear path for bacteria and fungi to transfer into the product. This is both the most common and most difficult container defect to detect, and remains hidden beneath the cap once it is applied. While micro leaks as small as 5 microns can still provide a path to bacteria and fungi, the typical flange defect is much greater in size and increases the probability of infection. The most common defect mode for single use contact lens blister packs are micro channel leaks due to wrinkles in the foil lidded seal.