Functional anatomy of the choroidal circulation: Methyl methacrylate casting of human choroid

Abstract

SummaryThe functional anatomy of the normal choroidal circulation in man is described from scanning electron microscopic examination of methyl methacrylate microvascular casts. Distal and para-optic short posterior ciliary arteries supply wedge-shaped areas of choroid. Regional variations in choriocapillary morphology are well recog nised; the lobules are densely packed at the posterior pole with a high capillary to inter-capillary ratio. Choroidal capillaries are flattened providing a large surface area for metabolic exchange with the retinal pigment epithelium. In acute choroidal ischaemia (from a variety of systemic disease), wedge shaped choroidal lesions may correspond to occlusion of short posterior ciliary arteries and geographic or focal lesions to occlusion of choroidal arterioles or choriocapillary lobules. MethodsThe anatomy of the choroidal circulation was examined from methyl methacrylate micro vascular casts prepared according to standard methods.42 The entire orbital contents and intracavernous part of the internal carotid artery were exenterated at autopsy 36-4 1 l hours post mortem (preserving the lids in situ). The ophthalmic artery was canulated, Primary infusion of phosphate buffered saline (PBS) was followed by gluteraldehyde 0.5% in PBS, at infusion pressures of 120-175 mmHg at physiological temperatures. Casting was achieved by secondary pedusation with 25-50 mls thinned methyl methacrylate resin (using a base of Batson's no.17, Polysciences) injected under manometric control until the resin hardened (7-10 minutes). The sur rounding tissue was corroded in six Molar pot assium hydroxide which was changed regularly and the casts washed in distilled water and air dried. The casts were gold sput ter coated (50 nm) and dissected appro· priately to include examination of the choroid. Ocular casts were examined by the scanning electron microscope (Hitachi S-520, Tokyo, Japan) either whole or as dissected fragments mounted on an aluminium stub, at 20 kv and magnifications of x22 to x1.3k. ResultsThe main findings are illustrated in Figure�

Comparison of amplitude-decorrelation, speckle-variance and phase-variance OCT angiography methods for imaging the human retina and choroid

“…The images of choriocapillaris obtained from single data sets have a "granular" appearance, only vaguely suggesting a mesh-like structure. Volume averaging yields a structure more convincingly resembling the appearance of choriocapillaris as imaged in histology samples [3]. A comparison between the three methods also shows differences in the influence of the retinal blood flow on the choriocapillaris imaging.…”

“…Choriocapillaris is a meshwork of densely packed, interconnected vessels forming characteristic mesh-like structures. It is organized in a lobular structure [3]. Blood with nutrients is delivered by arterioles located in the centers of the lobules.…”

Optical imaging of the chorioretinal vasculature in the living human eye

“…Anatomical studies of human choroidal circulation have reported that structural patterns and sizes of CC have regional variations over the retina (14,15). To demonstrate in vivo CC images at different retinal locations, we acquired pvOCT over peripheral retina (6°nasal and 12°inferior retina eccentricities) in the left eye (visual acuity: 20/60) of a 61-y-old female with geographic atrophy in the fovea.…”

Reflectance-based projection-resolved optical coherence tomography angiography [Invited]

“…The rbPR also suppresses these projection artifacts (Fig. 12(C1)) but shows a denser and more continuous mesh-like vascular network with small black pores where blood flow is absent, which better reflects the known scanning electron microscopy description of the vasculature [20]. [20].…”