Rohan Chawla1, Dheepak Sundar M1, Surbhi Agarwal2, Atul Kumar1

Purpose: To correlate the imaging characteristics of dark areas of certain retino-choroidal pathologies on Optical coherence tomography angiography (OCT-
A) and Indocyanine green angiography (ICG-A) Methods: 10 cases of each of the following retino- choroidal pathologies namely geographic atrophy (GA), serous pigment epithelial detachment (PED) and neurosensory detachment (NSD) secondary to central serous chorioretinopathy (CSC), drusenoid PED, choroidal neovascularization (CNV) and acute multifocal choroiditis were studied individually using Swept source OCT-A and Spectralis ICG-A. The imaging characteristics were critically analyzed. The hypocyanescent areas on ICG-A were correlated with the corresponding hypointense areas on OCT-A.
Results: All cases of GA showed hypocyanescent/ hypo areas on ICG-A/OCT-A with unearthing of underlying prominent larger choroidal vessels. All cases of Serous PED, drusenoid PED, NSD and acute choroiditis, showed dark areas on both ICG-A and OCT-A, but the larger underlying choroidal vessels were not seen through these areas. CNV revealed a hypercyanescent/hyperflow area with a surrounding hypo zone on both imaging modalities and again the larger underlying choroidal vessels were not seen through the hypointense zone.
Conclusion: Corresponding hypo areas at the level of choriocapillaris on OCT-A and ICG-A should be carefully analysed and they do not necessarily imply a loss of choriocapillaris or choroidal hypoperfusion. A definite conclusion of hypoflow/loss of chorioca- pillaris should be made if the underlying larger cho- roidal vessels get unearthed through this window. Else the hypointense defect may be due to shadow- ing or inability of the imaging modality to detect flow in presence of altered anatomy.