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Quantification of Normative Human Choriocapillaris Measures Across the Macula
Daniel X Hammer1, Katherine Kovalick2, Osamah J Saeedi2
1Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland, United States.
Purpose:
To assess macular choriocapillaris (CC) metrics in healthy volunteers (HVs) without ocular disease and demonstrate CC variations in patients with inherited retinal dystrophies (IRDs) using adaptive optics optical coherence tomography angiography (AO-OCTA).
Methods:
Twenty-one HVs and three IRD patients were imaged. Macular variation in 20 HVs in CC metrics (CC density, CC diameter, CC tortuosity, void diameter, void area, lobule count, lobule area, and RPE-CC distance) were assessed by imaging a 28° strip of overlapping AO-OCTA volumes (3° × 3°) from the optic nerve head to the temporal macula. En face projections of the CC at 1° intervals across the strip were created and metrics extracted using custom software.
Results:
CC density was mostly invariant across the macula at 0.523 ± 0.006, although it was slightly higher in the foveal region. The CC diameter decreased monotonically from 15.9 ± 0.7 µm in the nasal macula (-12°) to 14.2 ± 1.1 µm in the temporal macula (12°). Void measures also decreased from the nasal to the temporal macula: from 16.2 ± 1.4 µm to 14.6 ± 1.2 µm for void diameter and from 1418 ± 436 µm2 to 1243 ± 364 µm2 for void area. Lobule count peaked in the central macula. RPE-CC distance peaked at the fovea (fovea, 16.8 µm; periphery, ∼13-14 µm). CC tortuosity (1.17 ± 0.01) was constant across the macula. We observed a correlation with age in CC density, void diameter, and void area. AO-OCTA detected subclinical flow dropout in drusen regions. CC changes were observed in IRD patients with characteristics specific to the disease.
Conclusions:
Normative AO-OCTA-based CC metrics can provide insight into ocular disease pathology.
