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The highly vascular layer of the vertebrate eye, lying between the sclera and the retina.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the connective-tissue coat of the eye located between the retina and the sciera. It is through the choroid that metabolites and oxygen pass from the blood to the pigmentary epithelium and photoreceptors of the retina.

The choroid includes a suprachoroid layer facing the sciera, a layer of large veins, a layer of arteries and veins, the choriocapil-laris, and Bruch’s membrane. The suprachoroid layer consists of compact reticulin and collagenous fibers. It is rich in fibroblasts and melanocytes, whose processes run through the entire choroid. The arteries and veins of the choroid have a double endothelial lining and basal and adventitial layers. Bruch’s membrane is made up of an amorphous substance containing elastic reticulin and collagenous fibers. It is bounded on the inside by a cell membrane of pigmentary epithelium and on the outside by a porous membrane of capillary endothelium.

The choroid of some fishes and mammals, for example, ungulates, has a reflecting layer, or a mirror, that intensifies the light stimulation of the photoreceptors and increases the sensitivity of the eye to light.


Stebaeva, L. F., and O. V. Volkova. “Ul’trastruktura sosudistoi obo-lochki glaza krolika v norme i pri allergicheskom uveite.” Arkhiv anatomii, gistologii i embriologii, 1974, vol. 66, no. 2.
System of Ophthalmology, vol. 2. Edited by S. Duke-Elder. London, 1961.
Structure of the Eye: Proceedings of the Symposium at the Seventh International Congress of Anatomists. New York-London, 1961.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Choroidal melanoma metastasizes in approximately 50% of cases with liver involvement in 80-90% of cases and, unfortunately, metastatic disease is universally fatal (source: OMF).
CT is known to be thicker in the eyes of patients with ICSCR than in those with healthy eyes because of the widespread presence of large choroidal vessels (27).
Treatment effectiveness was evaluated for each patient by comparing pre- and post-injection subfoveal choroidal thickness and central macular thickness at each visit by paired-sample t-test.
Like other ocular structures, choroidal thickness may vary throughout childhood.
After choroidal nodules, periphlebitis is believed to be the second most important ocular manifestation of TB.
"The choroidal thickness significantly changed in the diabetes mellitus untreated group, and the main anatomical changes might result from the outer layer," the authors write.
* Tumour invasion to lamina cribrosa along with optic nerve sheath and choroidal invasion--Three patients
Spaide, "Optical coherence tomography angiography signs of vascular abnormalization with antiangiogenic therapy for choroidal neovascularization," American Journal of Ophthalmology, vol.
Optical coherence tomography is a noninvasive tool enabling the reproducible and quantitative assessment of the retinal layers, which currently remains the most precise method to measure retinal and choroidal thicknesses in vivo.
[5] reported that the peripheral punched-out chorioretinal lesions in POHS corresponded to areas of focal flow loss in the choriocapillaris and deeper choroidal layers on OCTA.
Enhanced depth imaging OCT (EDI-OCT) is a relatively new technique that uses light with a longer wavelength as it is more effective for choroidal scanning.