Microbial contamination in eye drops of patients in glaucoma treatment

Highlighting the Microbial Contamination of the Dropper Tip and Cap of In-Use Eye Drops, the Associated Contributory Factors, and the Risk of Infection: A Past-30-Years Literature Review

“…The sterility of eye drops should be, ideally, secured throughout the manufacturing process and the supply chain and maintained for the recommended duration of use, from opening to handling by the end user [ 10 , 11 ]. A literature review showed that the microbial contamination rate of preserved and preservative-free eye drops varied from 2.3 to 73% [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. The most important point was that fungal and bacterial microorganisms were cultured from the dropper tip, cap, and contents of eye drops [ 20 , 22 , 26 , 39 , 43 , 46 ,…”

“…Bacteria from the human commensal flora were the predominant isolated microorganisms [ 17 , 18 , 21 , 22 , 26 , 30 , 34 , 41 , 43 , 46 , 49 ], logically, since the contamination occurred after the bottle was opened. Limited growth of pathogenic bacteria and airborne environmental bacterial and fungal spores were also reported [ 15 , 24 , 29 , 34 , 43 , 50 ].…”

“…Microbial contamination was documented when used by patients at home and by healthcare professionals (HCP) in private clinics, in inpatient and outpatient settings, and in the operating room (OR) [ 15 , 17 , 18 , 19 , 36 , 37 , 39 , 41 , 43 , 49 ]. Numerous studies have reported inconsistent findings attributable to contributory factors [ 15 , 17 , 18 , 19 , 21 , 23 , 24 , 37 , 46 , 47 , 49 , 50 ]. The handleability of eye drops may pose an important risk of microbial contamination [ 10 ].…”

“…The handleability of eye drops may pose an important risk of microbial contamination [ 10 ]. The squeezability factors [ 11 ], missing the eyes completely during drug instillation [ 10 ], variable duration of use (preserved versus preservative-free [ 2 , 3 , 6 , 8 , 12 , 34 , 46 , 50 ], improper administration techniques, and age-related physical difficulties [ 17 , 24 , 32 , 37 , 47 , 49 ] were potential causes of microbial contamination at the dropper tip. Schein (1992) [ 41 ] proposed a cycle of eye drops and eye contamination.…”

“…Schein (1992) [ 41 ] proposed a cycle of eye drops and eye contamination. During the opening, recapping, and instillation, the dropper tip may inadvertently touch the ocular surface and cilia [ 24 , 37 , 41 , 43 , 49 , 50 ]. The contact of the dropper tip and eye or ocular annexes during drug administration may not only lead to the contamination of the former but also may contribute to cross-contamination with pathogenic microorganisms originating from an infected patient and affecting another patient with disrupted epithelial barriers or a compromised corneal epithelium using the same eye drops [ 43 ].…”