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A 5‐min time interval between two different dilating eyedrops increases their combined effect
Author(s) -
Saguet P.,
Charlot F.,
Mouriaux F.,
Lux A.L.,
Beraud G.,
Denion E.
Publication year - 2016
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2016.0607
Subject(s) - mydriasis , medicine , photopic vision , pupil , tropicamide , ophthalmology , phenylephrine , anesthesia , interval (graph theory) , eye drop , mathematics , optics , blood pressure , retinal , physics , combinatorics
Purpose Patients are usually advised to wait 5 min between eyedrops. This delay supposedly allows the first drop not to be washed out by the second one, thereby increasing the combined effect. However, in the only experimental study conducted in humans on the concurrent administration of two different eyedrops, the authors concluded that a 5‐min time interval between eyedrops did not increase their combined effect. Our study was designed to reassess this puzzling conclusion. Methods Using digital photographs shot in photopic conditions in 40 eyes of 20 healthy volunteers, we compared relative pupil surface (i.e. pupil to iris surface area ratios) before and after the administration of one drop of 10% phenylephrine and one drop of 0.5% tropicamide either immediately or after a 5‐min time interval. Results Waiting 5 min yielded a 5.6% relative pupil surface gain (p < 0.001) indicating an additional combined effect with a 5‐min time interval. Conclusions This prospective blind study is the first to show in humans that waiting 5 min between two different eyedrops increases their combined effect. This conclusion is probably the result of methodological refinements including challenging of the mydriasis by photopic conditions and use of pupil and iris surface areas, which may show differences that would be undetectable in terms of diameter.