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Noninvasive Tests Using Ultrasound (Excluding Imaging)
Published in Robert B. Northrop, Non-Invasive Instrumentation and Measurement in Medical Diagnosis, 2017
The arterial blood supply for the human eye comes from the ophthalmic artery (OA) which branches off the internal carotid artery (ICA) below the optic nerve. In addition to the eyes, the OA serves to supply other tissues with blood; notably the extraocular muscles, the sinuses, nasal tissues, etc. Here, we will only consider the OA's role in supplying the internal tissues of the eyeball. The central retinal artery (CRA) branches from the OA and enters the optic nerve and runs inside it. The CRA enters the rear of the eyeball along with the optic nerve fibers. Inside the rear of the eye, the CRA makes numerous fine branches; it also supplies the arterial Circle of Zinn surrounding the optic disc (“blind spot”) of the retina. Two, posterior ciliary arteries (PCAs) also branch off the OA and divide into some 10–20 branches, which run forward surrounding the optic nerve and pierce the choroid layer of the rear of the eyeball on the medial and lateral sides of the optic nerve. The branches from the short ciliary artery enter the sclera on the medial (nasal) side of the optic nerve, while the long ciliary artery's branches enter the lateral side of the eyeball and run forward between the sclera and the choroid to supply the ciliary body. They also anastomose with branches from the anterior ciliary arteries (ACAs) to form the circulus arteriosis iridus major that supplies the iris. The ACAs arise as branches of the muscle branches of the OA. Although the arterial anatomy of the eyeball is complex, the reader should appreciate that it is all derived from the ICA (Kronfeld 1943). Hence, any factor reducing pressure in the ICA will reduce arterial blood flow into the eyeball.
Swept-source optical coherence tomography imaging of the retinochoroid and beyond
Published in Expert Review of Medical Devices, 2020
Jayesh Vira, Alessandro Marchese, Rohan Bir Singh, Aniruddha Agarwal
Macular imaging in myopic eyes presents a unique challenge due to high axial lengths and shape of the globe. However, macular imaging in pathological myopia is extremely critical to detect pathologies such as myopic traction maculopathy, choroidal neovascularization, and other conditions such as dome-shaped maculopathy. SS-OCT imaging has been utilized in the evaluation of myopic fundi. Ishidia et al. in a retrospective analysis of 124 eyes of 112 consecutive patients with myopic CNV, SS-OCT showed that the connection between the CNV and the scleral vessels mainly originated from the short posterior ciliary arteries. OCTA images showed blood flow in active, scar, and atrophic phases [28]. Thus, SS-OCTA technology may further advance our understanding of CNV in these eyes in the future.