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Ischemic Optic Neuropathies
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
A brief recap of the blood supply of the optic nerve would help in understanding the ischemic insult to the optic nerve head (Figure 9.1). The anterior-most layer of the optic nerve head, consisting entirely of the retinal nerve fibers as they converge from all over the retina, is supplied by branches from the central retinal artery, the temporal aspect may be supplied by branches of the posterior ciliary artery (PCA) coming from the prelaminar region. The prelaminar part is supplied by centripetal branches from the peripapillary choroid, which in turn are drawn mainly from the short PCAs. There is no participation of blood supply from either the choriocapillaris or the central retinal artery in the prelaminar region. The peripapillary choroid that lies between the optic disc margin and the entry site of the short PCAs is a low-pressure system and vulnerable to hemodynamic variations. The laminar part has a rich capillary plexus and gets its blood supply from the centripetal branches from the short PCAs or from the circle of Zinn-Haller whenever present. Circle of Zinn-Haller is believed to have strict superior and inferior distribution.
Basic Principles of Laser
Published in Anita Prasad, Laser Techniques in Ophthalmology, 2022
The retina has a dual blood supply (retinal capillaries and choriocapillaris). Oxygen from choriocapillaris diffuses into the outer retina and is consumed by photoreceptors but does not reach the inner retina under normal circumstances.
Comparative Anatomy and Physiology of the Mammalian Eye
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
The capillary layer of the choroid, the choriocapillaris, is found in the inner portion just below the retinal pigment epithelium (RPE). It is responsible for the nutrition of the RPE and the outer retina and, in some species, for the entire retinal nutrition. The capillaries form a lobular network and are comprised of typical fenestrated endothelial cells surrounded by a basal lamina that surrounds and is shared by pericytes and smooth muscle cells.3,33,115 These lobules are supplied by a central arteriole and are surrounded by a ring of postcapillary venules.33 These vessels are permeable to fluorescein and horseradish peroxidase. Between the choriocapillaris and the RPE is Bruch’s membrane which, when fully developed, is comprised of five layers: (1) the basement membrane of the RPE, (2) an inner collagenous zone, (3) elastic layer, (4) outer collagenous zone, and (5) the basement membrane of the capillary endothelial cells.3,33 In animals with a cellular tapetum the basal lamina of the RPE and the choriocapillaris fuse, obliterating the other three layers in the region overlying the tapetum.3 Venous drainage from the choroid occurs in four quadrants where blood collects in an ampulla and then drains via one of four vortex veins which penetrate the sclera.
Tamoxifen related chorioretinal structural changes
Published in Cutaneous and Ocular Toxicology, 2023
İnci Elif Erbahçeci Timur, Vehbi Açıkgöz, Nagihan Uğurlu, Bülent Yalçın, Mehmet Ali Nahit Şendur, Mutlu Hızal, Halil Kara
Although tamoxifen-related retinal toxicity is rare, central serous chorioretinopathy (CSCR) [9], pacyhchoroid pigment epitheliopathy (PPE) [10,11], and alterations in choroidal thickness [12] were recently reported as tamoxifen-related impairments. PPE and CSCR are pachychoroid spectrum disorders, which have been defined in 2013 as subfoveal choroidal thickness of 300 μm or more [13]. The choroid has the highest amount of vascular tissue of the human body and supplies the posterior segment of the eye, which consists of choriocapillaris, the outer layer with large blood vessels known as Haller’s layer and the inner layer with small and medium vessels known as Sattler’s layer. Measuring choroidal thickness using enhanced depth imaging (EDI) with spectral domain optical coherence tomography (SD-OCT), identifying the vascular layer and stroma of the choroid by the binarisation method is used to determine the pathophysiology of retinochoroidal conditions.
Resilience of the Photoreceptors in Posterior Multifocal Placoid Pigment Epitheliopathy Observed by Microperimetry over Time
Published in Ocular Immunology and Inflammation, 2022
Fabio Scarinci, Monica Varano, Mariacristina Parravano
Because the foveola and perifoveal macula are completely avascular, their oxygen supply depends mainly on the oxygen source primarily via diffusion from the choroidal circulation and only minimally from the retinal circulation.21,22 Therefore, the impaired perfusion at the choriocapillaris and choroid level might lead to decreased perifoveal capillary blood flow. This in turn can cause dysfunction of the epithelium as well as photoreceptor cells expressed by diminished retinal sensitivity on microperimetry evaluation. Therefore, although our findings do not clarify whether the changes of epithelial and photoreceptor cells could precede the microvascular changes at the choriocapillaris level; however, they highlight the importance of the choriocapillaris in the pathophysiology of APMPPE and its influence on persisting visual impairment and health status of the photoreceptor in the whole macula area.
Choriocapillaris Assessment In Patients Under Mek-Inhibitor Therapy For Cutaneous Melanoma: An Optical Coherence Tomography Angiography Study
Published in Seminars in Ophthalmology, 2021
Giuseppe Fasolino, Gil Awada, Jorgos Socrates Koulalis, Bart Neyns, Peter Van Elderen, Robert W Kuijpers, Pieter Nelis, Marcel Ten Tusscher
The advent of OCTA and the ability to study the 3-dimensional vascular changes in vivo provides us with important insights into the pathogenesis of different pathologies and allows for in-vivo visualization of changes, previously only seen in histopathologic specimens. OCTA has shown highly reproducible results in the retinal capillaries of healthy and pathological eyes.25–27 However, the quantification of choriocapillaris flow voids is still a matter of heated debate. It has already been demonstrated that different algorithms to calculate absolute vessel densities are not mutually comparable. Each algorithm has the possibility to differentiate healthy from affected eyes, although with different discriminatory abilities. This implies that longitudinal follow up should always be performed using the same algorithm.28 We used a similar method to determine the choriocapillaris flow void parameters as described by Matet et al.8 A big difference in our approach was the use of 6 × 6 mm scans for the calculation of the SCP and DCP VAD and VSD. As a consequence we had to obtain 3x3mm scans for calculation of the flow void parameters by using imageJ to select a 200 × 200 pixel image around the center of our 400 × 400 pixel images. This results in a lower resolution, as the AngioVueHD imaging volume of a 6 × 6 mm scan consists of 400 × 400 A-lines, while the imaging volume of a 3x3mm scan consists of 304 × 304 A-lines.