Angioid streaks
Angioid streaks, also called Knapp streaks or Knapp striae are small breaks in Bruch's membrane
Bruch's membrane
Bruch's membrane is the innermost layer of the choroid. It is also called the vitreous lamina, because of its glassy microscopic appearance.It is 2–4 μm thick.-Layers:Bruch's membrane consists of five layers :...

, an elastic tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 containing membrane of the retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

 that can become calcified and crack.

They were first described by Robert Walter Doyne
Robert Walter Doyne
Robert Walter Doyne was a British ophthalmologist. He studied medicine in Oxford, Bristol and St. George's Hospital in London. In 1886 he founded the Oxford Eye Hospital, and in 1909 became the first president of the Oxford Ophthalmological Congress....

 in 1889 in a patient with retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

l hemorrhages. A few years later, ophthalmologist Hermann Jakob Knapp
Hermann Jakob Knapp
Hermann Jakob Knapp was a German-American ophthalmologist who was born in Dauborn, Nassau. He earned his medical degree from the University of Giessen in 1854. As a young physician he studied with Franciscus Cornelis Donders in Utrecht, William Bowman in London, Albrecht von Graefe in Berlin and...

 called them "angioid streaks" because of their resemblance to blood vessels. From histopathological
Histopathology refers to the microscopic examination of tissue in order to study the manifestations of disease...

 research in the 1930s, they were discovered to be caused by changes at the level of Bruch's membrane
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...

. Presently, it is believed that its pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

 may be a combination of elastic degeneration of Bruch's membrane, iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 deposition in elastic fibers from hemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...

 with secondary mineralization, and impaired nutrition due to stasis
Stasis (medicine)
In medicine, stasis is the state in which the normal flow of a body liquid stops, for example the flow of blood through vessels or of intestinal contents through the digestive tract....

 and small vessel occlusion
Vascular occlusion
Vascular occlusion is a sudden blockage of a blood vessel, usually with a clot. It differs from thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major vein, it can, in some cases, cause deep vein thrombosis. The condition is...


Angioid streaks are often associated with pseudoxanthoma elasticum
Pseudoxanthoma elasticum
Pseudoxanthoma elasticum , also known as Grönblad–Strandberg syndrome, is a genetic disease that causes fragmentation and 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), but have been found to occur in conjunction with other disorders, including Paget's disease
Paget's disease
Sir James Paget, a surgeon and pathologist, described several diseases, including:* Paget's disease of bone * Paget's disease of the breast* Paget-Schroetter disease* Extramammary Paget's disease...

, sickle cell anemia and Ehlers-Danlos Syndrome
Ehlers-Danlos syndrome
Ehlers–Danlos syndrome is a group of inherited connective tissue disorders, caused by a defect in the synthesis of collagen . The collagen in connective tissue helps tissues to resist deformation...

. These streaks can have a negative impact on vision due to choroid
The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye , while in the outlying areas it narrows to 0.1 mm...

al neovascularization
Neovascularization is the formation of functional microvascular networks with red blood cell perfusion. Neovascularization differs from angiogenesis in that angiogenesis is mainly characterized by the protrusion and outgrowth of capillary buds and sprouts from pre-existing blood vessels.In...

 or choroidal rupture. Also, vision
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...

 can be impaired if the streaks progress to the fovea
The fovea centralis, also generally known as the fovea , is a part of the eye, located in the center of the macula region of the retina....

 and damage the retinal pigment epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...

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