Bruch's membrane is the innermost layer of the

choroid The choroid, also known as the choroidea or choroid coat, is a part of the uvea, the vascular layer of the eye, and contains connective tissues, and lies between the retina and the sclera. The human choroid is thickest at the far extreme rear ...

of the eye. It is also called the ''vitreous lamina'' or ''Membrane vitriae'', because of its glassy microscopic appearance. It is 2–4 μm thick.

Layers

Bruch's membrane consists of five layers (from inside to outside): #the

basement membrane The basement membrane is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between Epithelium, epithelial tissues including mesot ...

of the

retinal pigment epithelium The pigmented layer of retina or retinal pigment epithelium (RPE) is the pigmented cell layer just outside the neurosensory retina that nourishes retinal visual cells, and is firmly attached to the underlying choroid and overlying retinal visual ce ...

#the inner collagenous zone #a central band of elastic fibers #the outer collagenous zone #the

of the choriocapillaris The retinal pigment epithelium transports metabolic waste from the photoreceptors across Bruch's membrane to the choroid.

Embryology

Bruch's membrane is present by midterm in fetal development as an elastic sheet.

Pathology

Bruch's membrane thickens with age, slowing the transport of metabolites. This may lead to the formation of

drusen Drusen, from the German word for ''node'' or ''geode'' (singular, "Druse"), are tiny yellow or white accumulations of extracellular material that build up between Bruch's membrane and the retinal pigment epithelium of the eye. The presence of a ...

age-related macular degeneration Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, som ...

. There is also a buildup of deposits (Basal Linear Deposits or BLinD and Basal Lamellar Deposits BLamD) on and within the membrane, primarily consisting of phospholipids. The accumulation of lipids appears to be greater in the central fundus than in the periphery. This build up seems to fragment the membrane into a lamellar structure more like puff-pastry than a barrier. Inflammatory and neovascular mediators can then invite choroidal vessels to grow into and beyond the fragmented membrane. This neovascular membrane destroys the architecture of the outer retina and leads to sudden loss of central vision – wet age related

macular degeneration Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Over time, however, som ...

Pseudoxanthoma elasticum Pseudoxanthoma elasticum (PXE) is a genetic disease that causes mineralization of elastic fibers in some tissues. The most common problems arise in the skin and eyes, and later in blood vessels in the form of premature atherosclerosis. PXE is cau ...

myopia Near-sightedness, also known as myopia and short-sightedness, is an eye disease where light focuses in front of, instead of on, the retina. As a result, distant objects appear blurry while close objects appear normal. Other symptoms may include ...

and trauma can also cause defects in Bruch's membrane which may lead to

choroidal neovascularization Choroidal neovascularization (CNV) is the creation of new blood vessels in the choroid layer of the eye. Choroidal neovascularization is a common cause of neovascular degenerative maculopathy (i.e. 'wet' macular degeneration) commonly exacerbated ...

. Alport's Syndrome, a genetic disorder affecting the alpha(IV) collagen chains, can also lead to defects in the Bruch membrane such as 'dot and fleck' retinopathy.

Angioid streaks Angioid streaks, also called Knapp streaks or Knapp striae, are small breaks in Bruch's membrane, an elastic tissue containing membrane of the retina that may become calcified and crack. Up to 50% of angioid streak cases are idiopathic. It may oc ...

cause calcification, thickening and breaks in Bruch's membrane.

Eponym

Bruch's membrane was named after the German anatomist Karl Wilhelm Ludwig Bruch.

References

External links

Pictures
at

National Eye Institute The National Eye Institute (NEI) was established in 1968. It is located in Bethesda, Maryland, United States. The NEI is one of 27 institutes and centers of the US National Institutes of Health (NIH), an agency of the US Department of Health and ...

{{DEFAULTSORT:Bruch's Membrane Human eye anatomy