Significance: Pharmaceutical companies recommend discarding ophthalmic drugs 28 days after opening. This study shows that diagnostic eye drops have a low risk of contamination over a 7-month period in a controlled clinical setup. The diagnostic efficiency seems to be preserved over this period.
Purpose: The aim of this study was to evaluate the preservation period and the efficacy of ophthalmic preparations, such as 0.5% proparacaine hydrochloride, 1% tropicamide, 2.5% phenylephrine hydrochloride, and 1% cyclopentolate hydrochloride ophthalmic solution in a clinical and controlled setting.
Methods: Thirty-eight primary eye care students were recruited to participate in the study. They used 25 bottles of each diagnostic drop at the Clinique Universitaire de la Vision for a 7-month period. An analysis of the bacterial contamination was repeated 10 times using both an agar plate and a nutrient broth at 0, 2, 4, 6, and 8 weeks and at 3, 4, 5, 6, and 7 months. The anesthetic, mydriatic, and cycloplegic effects were tested after 7 months of use and compared with nonopened ophthalmic bottles.
Results: During the 7-month period, 4971 drops of proparacaine, 3219 drops of tropicamide and phenylephrine, and 1896 drops of cyclopentolate were administered to the patients. A total of 226 contacts between bottles and biological tissues were reported. After the 10 inoculation sessions on the agar medium at the predetermined times, no bacterial and fungal contamination was noted. No patient reported eye infections for 2 weeks after the drop instillation. Moreover, there was no difference in the efficacy when compared with new drops.
Conclusions: According to the results of the current study, diagnostic eye drops can be used with a low contamination risk beyond the recommendation date of 28 days up to 7 months, with the same efficacy, in a controlled clinical context.