title: Force requirements in topical medicine use--the squeezability factor.
abstract: BACKGROUND
  Patient compliance is essential to ensure efficacious treatment. The ease of topical drop delivery is of paramount importance. At least 50% of patients report difficulty in self-administration of topical ocular medicine. The two most frequently reported causes of difficulty include aiming the bottle and squeezing the bottle.
  
  
  OBJECTIVE
  The aims of this study were to identify (I) the force required to deliver a single drop from a bottle (the squeezability factor), (II) are some bottle designs easier to use than others? (III) Do compliance aids reduce the finger strength required to deliver an eye drop?
  
  
  METHODS
  We measured the force required to deliver a single drop from a variety of commonly used ophthalmic preparations. Force was slowly applied at the midpoint along the bottle until a drop fell from the tip. Compliance aids were also tested with this technique.
  
  
  RESULTS
  We report a wide variation in the force requirements needed to use topical medicines. Three of the four compliance aids tested increased force requirements but may have had other beneficial effects by altering the grip on the medicine bottle.
  
  
  CONCLUSIONS
  This study highlights the large variability in force required to deliver a single drop using the ophthalmic preparations and compliance aids tested. We feel our results will be of interest and relevant to prescribing physicians and manufactures alike.
authors.affiliation: Department of Ophthalmology, James Cook University Hospital, Cleveland, UK. dralanconnor@hotmail.com
authors.forename: A J
authors.initials: AJ
authors.lastname: Connor
authors.forename: P S
authors.initials: PS
authors.lastname: Severn
mesh_terms: D000287:Administration, Topical; D004349:Drug Packaging; D006801:Humans; D009883:Ophthalmic Solutions / Q000008:administration & dosage*; D010349:Patient Compliance; D011312:Pressure; D012646:Self Administration; D012656:Self-Help Devices / Q000592:standards; D011795:Surveys and Questionnaires
chemical_list: D009883:Ophthalmic Solutions