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 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), ...

of the

eye 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 ey ...

. 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 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 vision, blurred or vision loss, no vision in the center of the visual field. Early on there are often no sym ...

(AMD).

Classification

Drusen associated with aging and macular degeneration are distinct from another clinical entity, optic disc drusen, 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 a high-resolution imaging technique with most of its applications in medicine and biology. OCT uses coherent near-infrared light to obtain micrometer-level depth resolved images of biological tissue or oth ...

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,

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, directin ...

, and Heinrich Müller, 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 exte ...

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 geology, geological secondary formation within sedimentary rock, sedimentary and volcanic rocks. Geodes are hollow, vaguely spherical rocks, in which masses of mineral matter (which may include crystals) are secluded. The crys ...

, 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, 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 radiation ...

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

and

lipids Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins Vitamin A, A, Vitamin D, D, Vitamin E, E and Vitamin K, K), monoglycerides, diglycerides, phospholipids, and others. The fu ...

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. It contains connective tissues, and lies between the retina and the sclera. The human choroid is thickest at the far extreme rear o ...

. Several trace elements are present in drusen, probably the most concentrated being zinc. The protein composition of drusen includes apolipoproteins 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 humoral, innate immune system and enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inf ...

. 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 ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

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 systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

Diagnosis

Usually being

asymptomatic Asymptomatic (or clinically silent) is an adjective categorising the medical conditions (i.e., injuries or diseases) that patients carry but without experiencing their symptoms, despite an explicit diagnosis (e.g., a positive medical test). P ...

, 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

{{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