Topographic Analysis of the Choriocapillaris in Intermediate Age-related Macular Degeneration

To quantitate regional differences in the choriocapillaris (CC) of patients with intermediate age-related macular degeneration (iAMD), using swept-source optical coherence tomography angiography (SS-OCTA) imaging. Cross-sectional study. Subjects were imaged with the SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc, Dublin, California, USA). The CC en face images were first compensated for the signal attenuation caused by drusen by using the structural information from the same slab. Subsequently, for each eye, 2 compensated CC en face images generated from 2 different OCTA volume scan sets were registered and averaged. The averaged CC images were then exported to ImageJ and binarized for subsequent quantitative analysis. In addition to the analysis of the whole averaged CC en face image in iAMD eyes, quantitative analysis was also performed in 3 different regions: (1) drusen region, (2) 150-μm-wide ring around the drusen border, and (3) drusen-free region. Thirty eyes (30 patients) with iAMD and 30 healthy eyes from 30 controls were enrolled. Compared with controls, iAMD eyes displayed a lower number of signal voids (median and interquartile range [IQR]: 2561 and 2343-2746 vs 2734 and 2558-2834; P = .013), a greater signal void average size (median, IQR: 581.9 μm2, 466.1-726.9 μm2 vs 503.8 μm2, 429.1-576.8 μm2; P = .027), and a greater total signal void area (median, IQR: 26.0%, 22.1%-29.6% vs 23.8%, 21.2%-26.4%; P = .038). In multiple regression analysis, the presence of iAMD was not significantly associated with any of the CC variables. By contrast, the drusen region area was significantly associated with CC alterations. In the evaluation of the iAMD group, both the area underneath drusen and the 150-μm-wide ring region around drusen were characterized by an increased total signal void area (P = .005 and P = .045, respectively) vs the drusen-free region. Intermediate AMD eyes demonstrated increased CC flow impairment, which co-localizes to the area of CC beneath and immediately surrounding drusen.