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Wait before extrapolating rather than wait between two eyedrops! … The 1974 Chrai et al.'s study on the albino rabbit may not apply to humans
Author(s) -
Bailleul H.,
Beraud G.,
Denion E.
Publication year - 2017
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.1755-3768.2017.0s064
Subject(s) - pilocarpine , saline , ophthalmology , medicine , pupil , iris (biosensor) , anesthesia , optics , physics , computer security , psychiatry , computer science , biometrics , epilepsy
Purpose The recommendation of having patients waiting 5 minutes between two eyedrops instillation is based on an experimental work conducted by Chrai et al. in 1974 on the albino rabbit. In this work, instillation of pilocarpine eyedrops was followed by instillation of saline eyedrops after 30 seconds and 2 minutes with as few as 4 rabbits and permitted a decreasing of the maximum difference in pupillary diameter respectively by 44% and 17.5%. The present study was undertaken to assess the validity of these findings in humans. Methods Twenty‐four healthy volunteers were enrolled from March 2016 to April 2017. Eyeballs were photographed in a completely dark room with an infrared camera at baseline, 40 minutes after instillation of 1% pilocarpine and 40 minutes after instillation of 1% pilocarpine eyedrops followed by the instillation of saline eyedrops immediately afterwards or 5 minutes later. Pupil to iris surface ratios were calculated and differences of ratios between baseline and 40 minutes (i.e. myosis gain) were compared with Wilcoxon test. Results The mean ( SD ) myosis gain was 0.176 (0.089) with 1% pilocarpine alone; 0.165 (0.086) with 1% pilocarpine immediately followed by saline eyedrops (p = 0.652) and 0.167 (0.087) with pilocarpine followed 5 minutes later by saline eyedrops (p = 0.731). Only some eye colours significantly influenced the myosis gain in multivariate analysis. Conclusions Despite using pupil/iris surface ratios (more sensitive than diameter measurements), and more subjects (24 versus 4) our study fails to confirm the results found by Chrai et al.'s in the albino rabbits. While awaiting for the issue of the time interval between eyedrops in humans to be further investigated, one should be cautious with extrapolation of Chrai et al.'s conclusions in the albino rabbits to humans.