Within-day changes in luminal, stromal choroidal thickness, and choroidal vascularity index in healthy adults

Purpose: To investigate topographical and within-day changes in the choroidal vascularity index and its association with choroidal thickness parameters (total, luminal, and stromal thickness) among young adults. Methods: Choroidal thickness and vascularity index were measured in 28 healthy young adults (age mean ± standard deviation [SD]: 25 ± 3.0) using spectral-domain optical coherence tomography. Participants were divided into three refractive groups: emmetropes, myopes, and high myopes. Choroidal parameters were evaluated in the macular and peripheral regions in the superior and inferior regions at two time points during the day; in the morning (at 7 am) and in the afternoon (at 1 pm). Results: All investigated choroidal thickness parameters showed a significant topographical variation across the vertical meridian, between the foveal (270 ± 89 μm, 170 ± 45 μm, and 111 ± 47 μm, respectively) and peripheral (246 ± 68 μm, 160 ± 39 μm, 86 ± 36 μm, respectively). The superior choroid was thicker in all thickness parameters compared to the inferior choroid. A significant increase in the vascularity percentage was seen from the fovea (61.8 ± 7%) toward the periphery (66.4 ± 7%). Thinner choroidal parameters were associated with high myopia, whereas an increase in the vascularity index was observed in high myopes. Significant within-day changes were observed in all choroidal thickness parameters, which were slightly reduced in the afternoon. The choroidal vascularity index (CVI) increased from 61.3 ± 5.3% in the morning and 63.2 ± 5.8% in the afternoon. High myopes exhibited reduced within-day amplitude in stromal thickness. Conclusion: All parameters showed significant regional variations. Myopia is associated with greater thinning in stromal thickness rather than vascular thickness. Only high myopes experienced reduced within-day change amplitudes in stromal choroidal thickness that was more predominant in the foveal and parafoveal regions.