Evaluation of the Effect of a Novel β3-Adrenergic Agonist on Choroidal Vascularity

To determine the effect of the new β3-agonist (mirabegron), which is used for overactive bladder (OAB) treatment, on central retinal thickness (CRT) and choroidal vascularity.

The 26 eyes of 26 cases using 50 mg tablet mirabegron once per day for OAB were included in this prospective case control study. The CRT, choroidal thickness (ChT), and choroidal vascularity were measured at baseline, week 1 (W1), month 1 (M1), month 2 (M2), and month 3 (M3). Subfoveal ChT measurement included the total subfoveal choroidal thickness (SFCT), and the small and large choroidal vessel layer (SCVL and LCVL) thickness. The total choroidal area (TCA), lumen area (LA), stromal area (SA), stroma/lumen ratio, and choroidal vascularity index (CVI) were measured with the Image-J software.

The largest SFCT increase compared to baseline was at M1 (26.8 ± 40.8 µm, P = 0.001). The subfoveal SCVL thickness showed a significant decrease at M2 and M3 (-6.0 ± 8.9 µm, P = 0.002; -7.8 ± 13.4 µm, P = 0.046, respectively). LCVL thickness showed a significant increase at W1, M1, and M2, with the largest at M1. CVI showed a significant increase at M1, M2, and M3 (P < 0.05 for all). The TCA, LA, and SA showed a significant increasing trend at all follow-up periods. LA/SA decreased at W1 because of stromal expansion but increased at M3 with more prominent vascular dilatation. CRT values showed no significant change.

Mirabegron had a significant effect on choroidal thickness. Choroidal vascular response is in the form of narrowing in the choriocapillaris and enlargement in the Haller's layer.