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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 It might be outdated or ideologically biased.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 ?
Various studies have shown abnormalities of choroidal circulation in patients of CSCR.8,9 Indocyanine green (ICG) angiography-based studies have also shown that the hyper-permeability of choroid may be the etiological factor.10 The combined choroid and RPE dysfunction theory states that the retina and choroid are affected simultaneously.
The thickness of the choroid is reduced when the retina in animals [13, 14] and humans [15-17] is exposed to hyperopic defocus (image plane located posterior to the retina).
Compared to spectral-domain OCT centred at 800 [micro]m, the longer wavelengths enable deeper penetration of ocular tissues and allow a three-dimensional (3D) high contrast image of the choroid to be obtained.
This meta-analysis of 11 clinical trials involving 449 patients indicated that the amblyopic process may involve the choroid. Our results showed that the CT was thicker in the amblyopic eyes than in both the fellow and control eyes.
The choroid plays a role in emmetropization and refractive error development in animal species and humans and has been shown to be involved in the visual feedback pathway.
We explored the effects of MT3 on FDM in the guinea pig and the effects of MT3 treatment on mRNA and protein expressions for TGF-[beta]2 and HAS2 in the retina and choroid in the guinea pig.
The posterior retina and choroid were isolated by a 7 mm surgical trephine.
Traditional ways of measuring choroid have low image resolution and limitation in pregnant women.
The choroid is the vascular layer of the eye located on the outer region of the retina, and most of the nutrients in photoreceptors and RPE are dependent on the choroidal blood supply [34].
Perhaps in the near future, newly developed devices may enable wide-field automated choroidal measurements, thus providing a better understanding of the topographic variations of the three-dimensional vascular structure of the choroid.