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 Bruch's membrane is the innermost layer of the choroid 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 l ...

and 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 ...

of the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

. The presence of a few small ("hard") drusen is normal with advancing age, and most people over 40 have some hard drusen. However, the presence of larger and more numerous drusen in the

macula The macula (/ˈmakjʊlə/) or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around and is subdivided into the umbo, foveola, foveal avas ...

is a common early sign of 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 ...

(AMD).

Classification

Drusen are associated with aging and macular degeneration are distinct from another clinical entity,

optic disc drusen Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc.Golnik, K. (2006). Congenital anomalies and acquired abnormalities of the optic nerve, (Version 14.3). UptoDate (On-Line Seri ...

, which is present on the

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i ...

head. Both age-related drusen and optic disc drusen can be observed by

ophthalmoscopy Ophthalmoscopy, also called funduscopy, is a test that allows a health professional to see inside the fundus of the eye and other structures using an ophthalmoscope (or funduscope). It is done as part of an eye examination and may be done as part ...

Optical coherence tomography Optical coherence tomography (OCT) is an imaging technique that uses low-coherence light to capture micrometer-resolution, two- and three-dimensional images from within optical scattering media (e.g., biological tissue). It is used for medical ...

scans of the orbits or head, calcification at the head of the optic nerve without change in size of globe strongly suggests drusen in a middle-age or elderly patient. Whether drusen promote AMD or are symptomatic of an underlying process that causes both drusen and AMD is not known, but they are indicators of increased risk of the complications of AMD. 'Hard drusen' may coalesce into 'soft drusen' which is a manifestation of macular degeneration.

Pathophysiology

Around 1850, three authors,

Carl Wedl Carl Wedl (14 October 1815 – 21 September 1891) was an Austrian pathologist who was a native of Vienna. In 1841 he obtained his doctorate in Vienna, and subsequently practiced medicine in Ischl and Salzburg. In 1844 he took a scientific jou ...

Franciscus Donders Franciscus (Franz) Cornelius Donders FRS FRSE (27 May 1818 – 24 March 1889) was a Dutch ophthalmologist. During his career, he was a professor of physiology in Utrecht, and was internationally regarded as an authority on eye diseases, directi ...

, and

Heinrich Müller Heinrich Müller may refer to: * Heinrich Müller (cyclist) (born 1926), Swiss cyclist * Heinrich Müller (footballer, born 1888) (1888–1957), Swiss football player and manager * Heinrich Müller (footballer, born 1909) (1909–2000), Austrian ...

, gave drusen different labels. Drusen, the hallmark of AMD, were first described in 1854 by Wedl. Wedl named them

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...

bodies of the choroid and thought that they were incompletely developed cells. Franciscus Donders called them "Colloidkugeln" (colloid spheres). Later, Heinrich Müller named them by the German word for

geode A geode (; ) is a geological secondary formation within sedimentary and volcanic rocks. Geodes are hollow, vaguely spherical rocks, in which masses of mineral matter (which may include crystals) are secluded. The crystals are formed by the fill ...

, based on their glittering appearance. He was convinced that drusen originated from the nuclei of the pigment cells, which he believed to belong to the choroid. In view of their location between the

(RPE) and its vascular supply, the

choriocapillaris The capillary lamina of choroid or choriocapillaris is a layer of capillaries that is immediately adjacent to Bruch's membrane in the choroid. The choriocapillaris was first described in man by Hovius in 1702, although it was not so named until 1 ...

, it is possible that drusen deprive the RPE and

photoreceptor cell A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiatio ...

s of oxygen and nutrients. In some cases, drusen develop above the so-called pillars of the

that is the area between two micro vessels; although important variations are observed between different subtypes of AMD. Drusen in OCT

The source of the

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

and

lipids Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

in drusen is also not clear, with potential contributions by both the RPE and 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 ...

. Several trace elements are present in drusen, probably the most concentrated being zinc. The protein composition of drusen includes

apolipoproteins Apolipoproteins are proteins that bind lipids (oil-soluble substances such as fats, cholesterol and fat soluble vitamins) to form lipoproteins. They transport lipids in blood, cerebrospinal fluid and lymph. The lipid components of lipoproteins a ...

and oxidized proteins, likely originating from blood, RPE, and photoreceptors. Drusen composition also includes members of the

complement system The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and at ...

. Zinc in drusen has been suggested to play a role in drusen formation by precipitating and inhibiting the elements of the complement cascade, especially complement factor H. The presence of molecules that regulate

inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...

in drusen has led some investigators to conclude that these deposits are product of the

immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...

Diagnosis

Usually being

asymptomatic In medicine, any disease is classified asymptomatic if a patient tests as carrier for a disease or infection but experiences no symptoms. Whenever a medical condition fails to show noticeable symptoms after a diagnosis it might be considered asy ...

, drusen are typically found during routine eye exams where the pupils have been dilated.

Treatment

Laser treatment of drusen has been studied. While it is possible to eliminate drusen with this treatment strategy, it has been shown that this fails to reduce the risk of developing the choroidal neovascularisation which causes the blindness associated with age-related macular degeneration.

Notes

Mishra S, Goel S, Roy SS, Garg B, Parvin M, Saurabh K, Roy R. Multimodal imaging characteristics of refractile drusen. Indian journal of ophthalmology. 2019 Jan;67(1):128. {{Medical resources , DiseasesDB = 29371 , ICD10 = {{ICD10, H, 35, 3, h, 30, {{ICD10, H, 47, 3, h, 46 , ICD9 = , ICDO = , OMIM = 126700 , OMIM_mult = {{OMIM, 126600, , none {{OMIM, 611040, , none {{OMIM, 603075, , none {{OMIM, 134370, , none , MedlinePlus = , eMedicineSubj = search , eMedicineTopic = Drusen , MeshID = Eye diseases

Classification

Pathophysiology

Diagnosis

Treatment

See also

Notes