INNER CHOROIDAL FLOW SIGNAL ATTENUATION IN PACHYCHOROID DISEASE Optical Coherence Tomography Angiography

Purpose: To study zones of reduced inner choroidal flow signal, foci of reduced inner choroidal thickness, and pathologically dilated Haller layer vessels (pachyvessels) in eyes with pachychoroid disease using optical coherence tomography (OCT) and OCT angiography. Methods: Patients with treatment-naive pachychoroid disease were recruited. All patients prospectively underwent swept-source OCT and OCT angiography. Zones of reduced choriocapillaris flow were labeled and enumerated. Areas where reduced flow signal was attributable to masking/artifacts were excluded. Regions of inner choroidal thinning were identified on structural OCT and labeled. Overlap between reduced choriocapillaris flow and structural inner choroidal attenuation was quantified using Jaccard indices. The relationship of reduced flow to pachyvessels was recorded. Results: Twenty-four eyes of 19 patients were identified. All eyes exhibited at least one zone of reduced flow. A total of 146 flow signal attenuation zones were identified. Sixty-two (42%) of 146 zones showed overlap or proximity with structural inner choroidal thinning. The mean Jaccard index per eye was 0.10 (SD = 0.08). Pachyvessels were spatially related to 100 (68%) of 146 zones of flow attenuation. Conclusion: Zones of reduced choriocapillaris flow are prevalent in eyes with pachychoroid disease. Approximately 60% of these zones anatomically correlate with pachyvessels. Inner choroidal ischemia seems related to the pathogenesis of pachychoroid diseases.