Wide Variation of Squeezing Force and Dispensing Time Interval among Eyedropper Bottles

Abstract

Purpose. We aimed to investigate squeezing force and dispensing time interval of the first and second eye drops among a variety of eyedropper bottles and to clarify associated factors within these parameters. Methods. A total of 87 eyedropper bottles were involved in this study. We developed a squeezing force measuring system consisting of a syringe pump, digital force gauge, and custom-made test stand to measure the squeezing force and dispensing interval. The eyedropper bottle was housed in the system vertically, and measurements were repeated five times. We investigated the differences in squeezing force and dispensing interval by categories, including those that targeted ocular disease, brand or generic eyedroppers, shapes of eyedropper bottles, and the presence of a membrane filter inside the tip of the eyedropper bottle. Results. The mean squeezing forces of the first drop and the second drops were 8.3 ± 3.0 N and 10.4 ± 3.2 N, respectively. Both squeezing forces had a wide variation of more than threefold. A mean interval between the first and second drops was 3.1 ± 1.2 sec with a maximum difference of more than sevenfold. Round shapes of eyedropper bottles and the presence of filter membranes significantly increased the squeezing force. Conclusions. The squeezing force of eyedropper bottles was very wide, which may affect proper eye drop instillation. Unification of eyedropper bottles or developing mechanical aids may be useful for proper eye drop treatment.

Investigation of visual and physical factors associated with inadequate instillation of eyedrops among patients with glaucoma

“…In addition to aging [ 21 ], some musculoskeletal or neurological diseases may increase instillation failure. It has been reported that the force required to expel eyedrops sometimes exceeds the ability of some healthy subjects [ 22 ] and that the squeezing force of eyedropper bottles is very wide [ 23 , 24 ]. Approximately 20% of ophthalmic patients reported difficulty squeezing their eyedrop bottle.…”

Sterility of Ophthalmic Solutions as a Factor in the Evolution of Primary Packaging for Eye Drops: A Literature Review

“…The volume of a single dose is 30 μL. However, the porous gasket and hydrophilic membrane create significant resistance in the path of the drug flow, resulting in a fixed actuation force in the range of 17-20 N, which is lower than that of the Comod® and 3K® systems (41). One disadvantage of this technology is that the gasket and membrane structures may limit the use of low-viscosity formulations.…”