Premium Nahrungsergänzungsmittel | artgerecht

Choroid – Structure, Function and Diseases

The choroid is a highly vascular layer of the eye located between the retina and the sclera. It supplies the outer retinal layers with oxygen and essential nutrients.

Regular tips about health Regular tips about health

Things worth knowing about "Choroid"

The choroid is a highly vascular layer of the eye located between the retina and the sclera. It supplies the outer retinal layers with oxygen and essential nutrients.

What is the Choroid?

The choroid (also called choroidea) is a pigmented, richly vascularized tissue layer within the eye. It is situated between the retina on the inside and the sclera (the white outer coat of the eye) on the outside. Together with the ciliary body and the iris, it forms the uveal tract (the vascular tunic of the eye). In adults, the choroid is approximately 0.2 to 0.3 millimeters thick and is one of the most highly perfused tissues in the entire human body.

Structure of the Choroid

Histologically, the choroid is divided into several distinct layers:

Suprachoroid (lamina suprachoroidea): The outermost connective tissue layer bordering the sclera.
Haller layer: Contains large blood vessels (arteries and veins).
Sattler layer: Contains medium-sized blood vessels.
Choriocapillaris: A dense capillary network lying directly adjacent to the retinal pigment epithelium, responsible for nourishing the photoreceptors.
Bruch membrane: A thin basement membrane separating the choriocapillaris from the retinal pigment epithelium.

Functions of the Choroid

The choroid serves several vital roles in supporting visual function:

Nutrient supply: The choriocapillaris delivers oxygen and nutrients to the outer retinal layers, particularly the photoreceptors (rods and cones).
Thermoregulation: The high blood flow through the choroid dissipates heat generated by light absorption, helping to regulate retinal temperature.
Light absorption: Melanin pigment within the choroid absorbs scattered light, reducing optical noise and improving image clarity.
Intraocular pressure regulation: Changes in choroidal blood volume contribute to the regulation of intraocular pressure.

Diseases of the Choroid

Several conditions can affect the choroid and lead to serious visual impairment:

Age-Related Macular Degeneration (AMD)

In age-related macular degeneration, structural changes occur in the Bruch membrane and choriocapillaris, impairing the blood supply to the macula. In the wet form of AMD, abnormal blood vessels grow from the choroid into the retina, a process known as choroidal neovascularization (CNV).

Choroiditis

Choroiditis is an inflammation of the choroid, commonly occurring as part of posterior uveitis. It can be caused by infections (e.g., toxoplasmosis, tuberculosis, syphilis) or autoimmune conditions, and may lead to significant vision loss.

Choroideremia

Choroideremia is a rare, X-linked recessive inherited disorder characterized by progressive degeneration of the choroid, retinal pigment epithelium, and retina. It typically causes night blindness and progressive narrowing of the visual field.

Choroidal Melanoma

Choroidal melanoma is the most common primary intraocular tumor in adults. It arises from melanocytes within the choroid and can compromise vision as well as metastasize to distant organs, most frequently the liver.

Central Serous Chorioretinopathy

Central serous chorioretinopathy (CSC) is a condition in which fluid accumulates beneath the retina due to increased permeability of the choriocapillaris. It predominantly affects young to middle-aged men and can cause blurred vision and image distortion.

Diagnosis of Choroidal Conditions

Several diagnostic tools are available to evaluate the choroid:

Ophthalmoscopy (fundoscopy): Direct visualization of the fundus and choroidal structures.
Optical coherence tomography (OCT): High-resolution cross-sectional imaging of retinal and choroidal layers.
Fluorescein angiography: Imaging of retinal and choroidal vessels using a fluorescent dye.
Indocyanine green angiography (ICG): Particularly suited for evaluating choroidal circulation.
Ultrasound (B-scan): Used to detect choroidal tumors or detachments.

References

Forrester, J. V., Dick, A. D., McMenamin, P. G., Roberts, F., Pearlman, E.: The Eye: Basic Sciences in Practice. 4th edition. Elsevier Saunders, 2016.
Bhutto, I., Lutty, G.: Understanding age-related macular degeneration (AMD): Relationships between the photoreceptor/retinal pigment epithelium/Bruch's membrane/choriocapillaris complex. Molecular Aspects of Medicine, 33(4), 295–317, 2012. PubMed PMID: 22542780.
Spaide, R. F., Jaffe, G. J., Sarraf, D. et al.: Consensus Nomenclature for Reporting Neovascular Age-Related Macular Degeneration Data. Ophthalmology, 127(5), 616–636, 2020. PubMed PMID: 31630927.

Building Blocks for a Healthy Life

As an integrated manufacturer, we develop & produce evidence-based, patented, and non-patented formulations. We work exclusively with plant and natural extracts according to the strictest purity & quality standards.
The combination of science & modern technology with the laws of nature creates solutions consistently tailored to humans – for the highest good: health.

Most read entries

3 Posts in this encyclopedia category