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Influence of the Dropper Tip Design on the Size of Eye-drops

Luc Van Santvliet and Annick Ludwig

University of Antwerp (U.I.A.), Department of Pharmaceutical Sciences,
Laboratory of Pharmaceutical Technology and Biopharmacy, Antwerp (Belgium)

The present study aims at investigating the influence of the dropper tip design and the drop delivery method on the size of eye-drops dispensed from plastic dropper bottles. The size of drops dispensed from 13 different dropper tips under standard conditions of compressing the dropper bottle using a drop dispensing apparatus depends primarily on the outer orifice diameter of the tip. The diameter of the inner aperture, on the other hand, determines the flow of liquid through the capillary of the dropper tip and, consequently, also the drop size. Dispensing drops more slowly results in an average 5 % decrease in drop size. Instead of squeezing the body of the dropper bottle, an alternative drop delivery method consists of pressing the bottom of the bottle. Drops of an almost equal drop size can be dispensed in a shorter dispensing time and with less force from a tip with annular recess in its design using this alternative method. Varying the dispensing angle from 90° to 45°, o n the other hand, reduces the cross-sectional surface area at which the drop is formed and, consequently, smaller drops are dispensed.

Key words Drop dispensing · Dropper tip design · Eye drop size · Ophthalmic solutions