Correlation of choriocapillaris hemodynamic data from dynamic indocyanine green and optical coherence tomography angiography

Figures

• 

  Figure 1. Indocyanine green angiography without subtraction. (A–D) showed consecutive frames from video angiography. Each frame was 22/100 s apart. Dye first appeared in vessels in the peripapillary and macular area and progressed laterally along individual vessels.

• 

  Figure 2. Digital subtraction indocyanine green angiography of the first monkey. (A) Dye first entered the peripapillary area of choriocapillaris in regions around the optic disc and posterior pole. (orange arrows). (B) A irregular segmented pattern can be seen as the choriocapillaris around the optic disc fills. (C) Dye filling progressed radially to the macular region. Many units of variable size and shapes were discernible, separated from each other by dark zone. (D) Dye filling in the posterior pole region appeared fairly uniform.

• 

  Figure 3. Digital subtraction indocyanine green angiography of the second monkey. (A) Dye first entered the peripapillary area of choriocapillaris in regions around the optic disc and posterior pole. (orange arrows). (B) Units appear bright around the optic disc. (C) Dye filling progressed radially to the macular region. Many units of variable size and shapes were discernible, separated from each other by dark zones. (D) Dye filling in the posterior pole region appeared fairly uniform.

• 

  Figure 4. Digital subtraction indocyanine green angiography in which segmented pattern can be seen (same eye as Fig. 2). (A) We could define segment (functional lobule) as an area of fast flow surrounded by a perimeter of slow flow. The dye front appears first in the centre of each segmented unit and spread towards the perimeter of each unit in the macular region. In the next frame (0.2 s later), the central area becomes dark (B), which implies no change in fluorescence as compared with previous frame. The location of unit correlate well in the two images. The zones between adjacent segmented units appeared faintly brighter in (B) compared to in (A), which suggests a slow movement of the dye front in this region. Note that the organization of these zones is not regular in relation to the adjacent units. There was also a range of width, estimated between 50 and 200 µm. (C) Registration of (A—in red) and (B—in blue) highlighted the neighbouring units (functional lobules) which can be seen as red areas (fast flow) separated blue areas (slow flow).

• 

  Figure 5. Optical coherence tomography angiography of a 3 × 3 mm area centered over the fovea of the same eye as in Fig. 1. (A) showed choriocapillaris slab using boundaries of 17 µm below RPE to 33 µm below RPE. A uniform meshwork of bright areas which appear as continuous densely packed capillary network can be seen. This network appeared to have uniform characteristics in vessel density and size. In particular, a specific lobular or segmented structure was not a dominant feature. Additional slabs to visualize the posterior part of choriocapillaris using boundaries of 20–28 µm below RPE (B) and 26–33 µm below RPE (C) also showed a uniform meshwork as the dominant feature. Several tubular structures (arrow) can be seen which correlate to choroidal vessels which appear black in the slab with boundaries 25–40 µm below RPE (D).

• 

  Figure 6. Schematic of the progression in time of blood flow in the choriocapillaris units as observed in this study on ICGA. The red dots represent arterioles and the green dots venules which are randomly distributed (A). As blood enters the choriocapillaris via the arterioles, they expand and flow toward venules. The direction and extent of flow is governed by the pressure gradient and distance between the surrounding arterioles and venules (B, C). The flow from an arteriole outward would be more for a closer vein draining than a distant one. Zones between adjacent units that are last to fill are noted, which also vary in width and shape (D). Note that these darker zones do are not centered around draining venules, but represent regions furthest from arterioles. As the blood flow in central part of each unit becomes constant, dye flow was observed in the perimeter of each units and the zones between adjacent units (E, F).