The blood–retinal barrier, or the BRB, is part of the
blood–ocular barrier
The blood–ocular barrier is a barrier created by endothelium of capillaries of the retina and iris, ciliary epithelium and retinal pigment epithelium. It is a physical barrier between the local blood vessels and most parts of the eye itself, an ...
that consists of cells that are joined tightly together to prevent certain substances from entering the tissue of the retina. It consists of
non-fenestrated capillaries of the
retinal circulation and
tight-junctions between
retinal epithelial cells preventing passage of large molecules from
choriocapillaris into the
retina
The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...
.
Structure
The blood retinal barrier has two components: the
retinal vascular endothelium and the
retinal pigment epithelium
The pigmented layer of retina or retinal pigment epithelium (RPE) is the pigment
A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), ...
. Retinal blood vessels that are similar to cerebral blood vessels maintain the inner blood-ocular barrier. This physiological barrier comprises a single layer of
non-fenestrated endothelial cells, which have
tight junction
Tight junctions, also known as occluding junctions or ''zonulae occludentes'' (singular, ''zonula occludens''), are multiprotein Cell junction, junctional complexes between epithelial cells, sealing and preventing leakage of solutes and water. Th ...
s. These junctions are impervious to
tracer, so many substances can affect the metabolism of the
eyeball
An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system.
In higher organisms, the eye ...
. The
retinal pigment epithelium
The pigmented layer of retina or retinal pigment epithelium (RPE) is the pigment
A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), ...
maintains the outer blood–retinal barrier.
Clinical significance
Diabetic retinopathy
Diabetic retinopathy
Diabetic retinopathy (also known as diabetic eye disease) is a medical condition in which damage occurs to the retina due to diabetes. It is a leading cause of blindness in developed countries and one of the lead causes of sight loss in the wor ...
, eye damage that frequently occurs as a result of
diabetes
Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...
, is related to the breakdown of the blood–retinal barrier. The barrier becomes more leaky in patients with diabetic retinopathy.
Other animals
Animal model
An animal model (short for animal disease model) is a living, non-human, often genetic-engineered animal used during the research and investigation of human disease, for the purpose of better understanding the disease process without the risk of ha ...
s have shown that the blood–retinal barrier becomes more permeable to substances in
hypertensive
Hypertension, also known as high blood pressure, is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms itself. It is, however, a major risk ...
animals (those with high
blood pressure
Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...
).
[S Lightman, E Rechthand, C Latker, A Palestine and S Rapoport]
Assessment of the permeability of the blood–retinal barrier in hypertensive rats.
''Hypertension'', Volume 10, Pages 390-395. Retrieved on July 19, 2007.
See also
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References
{{DEFAULTSORT:Blood-retinal barrier
Angiology
Human eye anatomy