AIM: To evaluate the potential posterior segment effects of topical application of brimonidine-purite 0.15% through measurement of choroidal thickness(CT)in healthy eyes using enhanced depth imaging spectral-domain optical coherence tomography(EDI-SD-OCT).

METHODS: Thirty-two eyes of 32 healthy subjects were included in this prospective, placebo-controlled interventional clinical trial. They received one drop of topical preservative-free artificial tears as placebo for the first day and one drop of brimonidine-purite 0.15% for the second day. Intraocular pressure, ocular perfusion pressure(OPP), and EDI-SD-OCT were performed at baseline, at 1, 3 and 5h after the treatments.

RESULTS: Compared to the measurements obtained at baseline, the CT measurements obtained after the topical application of brimonidine-purite 0.15% significantly increased at the sub-fovea(P=0.001), at temporal 1500 μm to the fovea(P=0.003)and at nasal 1500 μm to the fovea(P=0.003). Choroidal thickness was unchanged in placebo group during the study(P >0.05). There was no significant reduction in the OPP in both groups(P >0.05). There were no adverse events during the study.

CONCLUSIONS: Contrary to expectations, topical administration of brimonidine-purite 0.15% resulted with thickening of sub-foveal, temporal and nasal CT. This might be related to altered auto-regulation mechanisms in choroidal vessels.