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Kazuhiro Kurokawa, Zhuolin Liu, Omer Pars Kocaoglu, Donald Thomas Miller; Imaging choriocapillaris with adaptive optics optical coherence tomography angiography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5915. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Histological studies have shown that morphometric changes of choriocapillaris occur with aging and disease onset, and therefore may be potentially sensitive biomarkers of outer retina health. Here we demonstrate that such morphometric parameters can be measured in the living human retina at the level of individual capillaries using adaptive optics (AO) and optical coherence tomography (OCT) angiography.
AO-OCT volume videos subtending a 1°×0.5° (h×v) field of view were acquired at 1° intervals between 1° and 7° temporal to fovea in two healthy subjects (49 and 31 years of age). The Indiana AO-OCT (λc=790 nm, Δλ=42 nm) operated in its 2-camera mode, a configuration that eliminated losses due to camera readout and balanced signal-to-noise ratio (SNR) with image acquisition speed (200 KHz A-line rate). To minimize detector drop-off and further improve SNR of the choriocapillaris layer, the coherence gate was positioned immediately behind the retina. The AO-OCT volumes were registered in all three dimensions with cellular level precision and then local correlation analysis was applied to the choriocapillaris layer for OCT angiography. The resulting en face choriocapillaris images were analyzed in terms of the following morphometric parameters: capillary lumen diameter, capillary fill factor, total capillary length per en face area, and depth separation of choriocapillaris from retinal pigment epithelium (RPE).
Choriocapillaris of both subjects was successfully imaged across the entire 0.5° to 7.5° temporal strip and quantified in terms of the morphometric parameters. Average and standard deviation values for the two subjects are as follows: lumen diameter (16.7±3.9 μm and 14.8±3.7 μm), capillary fill factor (56±2% and 53±1%), total capillary length per en face area (37.5±1.2 mm-1 and 38.6±1.3 mm-1), and separation of choriocapillaris from RPE layer (18.4±1.7 μm and 17.0±1.2 μm). No significant variation in the morphometric parameters was observed over the retinal eccentricities examined (0.5° to 7.5° temporal to the fovea) even though the overlying cone photoreceptor density varies by about 9 times.
AO-OCT angiography enables quantification of morphometric parameters of individual capillaries of the choriocapillaris in the living human eye.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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