Repeatability of choroidal optical coherence tomography angiography metrics in healthy young adults

Clinical relevance Assessment of choroidal perfusion plays an important role in evaluating ocular vascular status and may assist in managing vascular alterations in ocular and systemic disease.Background Optical coherence tomography (OCT) angiography enables non-invasive assessment of choroidal perfusion; however, repeatability across different depths remains unclear. This study evaluated within- and between-day repeatability of choroidal OCT angiography measurements in healthy young adults and the effect of image pre-processing.Methods Twenty healthy adults (18–35 years) underwent repeated imaging using Heidelberg Spectralis OCT angiography. Perfusion density was quantified in choriocapillaris and three custom slabs representing superficial, intermediate, and deep choroid. The standard (device-defined) choroidal slab was also analysed. Within-day repeatability used scans acquired 60 minutes apart, and between-day repeatability scans from different days at the same time. The influence of image pre-processing was assessed.Results Perfusion density differed significantly across layers, increasing from superficial to deep (p < 0.001), while the choriocapillaris did not differ from superficial or intermediate layers, it was lower than the deep choroid (p = 0.014). A significant regional effect was observed, with higher perfusion density in the central (1 mm) than inferior (2 mm) region (p = 0.009). Within-day repeatability was excellent (intraclass correlation coefficients > 0.90), with standard choroid showing highest stability. Between-day repeatability was good (intraclass correlation coefficients = 0.77–0.91), with the greater variability in deeper layers. Variability was lower in the 2 mm parafoveal zone compared to the 1 mm foveal zone in the standard and deep choroid (both p < 0.05). Image pre-processing significantly improved between-day repeatability for standard choroid (p < 0.05).Conclusion Choroidal perfusion metrics showed excellent within-day and good between-day repeatability, with systematic differences across layers and regions. Image pre-processing improved measurement precision, supporting OCT angiography as a reliable tool for clinical and research assessment of the choroid.