Effects of Two Commonly Used Mydriatics on Choroidal Thickness: Direct and Crossover Effects

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PURPOSE: To investigate the effect of 2 commonly used mydriatics on choroidal thickness using enhanced depth imaging optical coherence tomography (EDI-OCT). METHODS: In this prospective study, 90 healthy subjects were enrolled. The participants were randomly divided into 3 groups based on the application of drops. One eye of each subject received a drop of tropicamide 1% in the tropicamide group (n=30), a drop of phenylephrine 2.5% in the phenylephrine group (n=30), and a drop of artificial tear in the control group (n=30). Drops were given thrice at 5 min intervals. Subfoveal choroidal thickness (SFCT) was measured using EDI-OCT before and at 45 min after drop application in both the dilated eye and nondilated contralateral eye. RESULTS: The SFCT was significantly decreased after drop instillation in both the dilated eye and contralateral eye in the tropicamide group (P<0.001 and P=0.001, respectively) and in the phenylephrine group (P<0.001 and P=0.001, respectively). However, the SFCT did not significantly differ after drop instillation in either the dropped eye or contralateral eye in the control group (P=0.108 and P=0.695, respectively). CONCLUSION: The findings of the present study revealed that tropicamide and phenylephrine cause a decrease in choroidal thickness.