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The highly vascular layer of the vertebrate eye, lying between the sclera and the retina.



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.


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Structure of the Eye: Proceedings of the Symposium at the Seventh International Congress of Anatomists. New York-London, 1961.


References in periodicals archive ?
Tumour invasion to lamina cribrosa along with optic nerve sheath and choroidal invasion--Three patients
5 High myopia is characterized by excessive and progressive elongation of the globe, resulting in a variety of secondary fundus changes that may lead to visual impairment, including retinal detachment, myopic macular schisis, macular hole, choroidal neovascularization, and zonal areas of chorioretinal atrophy.
The differential diagnosis of this condition included central areolar choroidal dystrophy, geographic atrophy, and pathologic myopia.
On examination, choroidal metastases appear as pale subretinal lesions.
Histopathological studies have found a choroidal arteriole and vein expanding through the break in Bruch's membrane as CNV associated with AMD.
Sadda, "Diurnal variation of choroidal thickness in normal, healthy subjects measured by spectral domain optical coherence tomography," Investigative Ophthalmology and Visual Science, vol.
The retinal circulation has no autonomic innervation and is regulated by local factors [6] while the choroidal circulation is not autoregulated and is mainly controlled by sympathetic innervation [96].
The retina nerve fiber layer and choroidal thickness measurements were obtained through the Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany).
The pathogenesis underlying the process is choroidal neo-vascularization in which the blood vessels disrupt the Bruch's membrane and grow into the sub-retinal pigmented epithelial (RPE) space.
It has been demonstrated that submaximal exercise increases the choroidal blood flow velocity relative to the increase in mean arterial pressure (MAP) (Hayashi et al.
Choroidal tuberculosis is the most common initial manifestation of intraocular tuberculosis.
Previous authors have reported choroidal neovascularization (CNV) associated to papilledema (3, 4, 5).