Drusen

As Druze are called deposits of extracellular material beneath the retina. They are ubiquitous in all age groups, but take with increasing age in number and size to. They are considered as an early form of age- related macular degeneration. Druze cause per se does not restrict the vision, but can lead to disorders of color and contrast sensitivity.

Etymology and history

Drusen were first in 1855, in the first volume of the Archives of Ophthalmology, FC Donders described. He discovered spherical deposits beneath the retina of a 80 - year-old patient and groomed them. Based on the experiments carried out by him, he came to the conclusion to be able to compare most closely associated with colloid tissue:

But how is it call? For the moment, I know it not, in fact, but the idea of ​​the hybrid word Colloid is so stretchy that I do not believe to be indiscreet if I provisionally obtain for me is a place for these balls. I will therefore simply call Colloidkugeln.

He continues:

How and what to develop these balls? At first sight it seemed to me already probably before that they arise from the nuclei of the pigment cells. Further investigations have completely convinced me of the correctness of this conjecture.

This finding laid the foundation for the transformation theory of the origin of drusen. Just one year later, in 1856, H. Müller developed the so-called deposition theory that drusen deposits resulting from degradation products of the retina. He also introduced the term " strangles " a, on the basis of their appearance, which reminded him of the mineral stone formations. The term geode sat down finally by the international scientific literature.

Definition and forms

As Strangles is defined as a focal deposition of extracellular material between the basal lamina of the retinal pigment epithelium and the inner collagenous layer of Bruch's membrane called.

Already Donders described in his scholarly article the different appearance of drusen. Clinically today between hard and soft drusen. Depending on their edges, and furthermore of calcified drusen, if this funduscopically have a highly reflective whitish content Histologically, however, a much greater diversity was observed at different drusen forms. A similar diversity is found in the tomographic sections of the optical coherence tomography.

A more detailed assessment of the clinical significance of these different types of drusen in the progression of age-related macular degeneration is still pending.

Epidemiology

98.8 % of the total population have at least one druse. Here are small hard drusen ( less than 63 microns in diameter ) is by far the most common, what the conjecture suggests that it is these represent physiological phenomena without clinical significance. The prevalence of drusen than 63 microns in diameter and soft drusen increases with age; they can be found in around 60 % of all people over 75 years.

Formation

The precise mechanism of drusen is still unknown despite numerous scientific research to a large extent. Generally, a mixture of the above-mentioned transformation and deposition theory is assumed. Here, for example, serve by oxidative stress and the appropriate genetic predisposition predamaged pigment as a trigger for immune- mediated processes in which especially the complement system seems to play a major role. Subsequently there is the deposition of immune complexes, proteins, and lipids.

Drusen constituents

Major component of drusen forming lipids, especially cholesterol, which is also blamed for the yellowish appearance of drusen. In addition to carbohydrates, zinc and extracellular matrix components found. To date, at least 129 different proteins could also be identified within the Druze, of which the majority are associated with inflammation or immune -associated processes. In addition, can be found in drusen also various cell components, such as lipofuscin and melanin, to complete cells, such as dendritic cells.

Outcome

About the further development of drusen can only speculate on the basis of histological studies. In the physiological form of drusen, it is believed that after the healing of the pigment epithelium deposits is piped through Bruch's membrane and are absorbed by the choroid. The Druze therefore disappears without a trace after some time. Especially with the observed in the older age soft drusen, however, irreversible damage to the pigment epithelium appears to be present, which will be promoted through the development of a geode. In addition, the removal of drusen constituents likely to be considerably reduced by age-related thickened Bruch's membrane. It finally comes to a complete degeneration and atrophy of the RPE over the Druse and, consequently, to a degeneration of the overlying photoreceptors. This stage is defined as the onset of age-related macular degeneration ( AMD).

Drusen as risk factor for age -related macular degeneration

The incidence of soft drusen with or without pigmentary changes, characterized by definition, the clinical picture of age-related maculopathy. Hard drusen is currently attached no clinical significance. The age-related maculopathy is often referred to as " early form " of AMD. Based on these classifications, which in the AMD flows flowing, the large-scale multicenter study Age-Related Eye Disease Study ( AREDS ) was built in the 1990s, which set itself the goal of the clinical manifestations and trends of age-related maculopathy and degeneration to investigate. The number of drusen and their total surface area per eye was determined to be clinically significant risk factor for the development of AMD. About the exact risk potential the Estimates vary, however. Studies report a risk develop in existing bilateral drusen within the next 5 years, a wet AMD, between 0.2 % and 40 %. These large differences suggest that there are a variety of different types of drusen, need to be developed for the appropriate study models.

Clinic

Druze cause per se not impaired eyesight and therefore are usually an incidental finding. In some cases, however, reported in most large number of drusen of disorders of contrast sensitivity and color perception, as well as decrease in sensitivity in the central visual field.

Primary are Druze understood as an early form of AMD, they find themselves but also in other diseases, such as pigmented nevi or malignant melanoma above. Likewise Druze have been reported in long-standing central serous retinopathy. In addition, a correlation of drusen and glomerulonephritis type II was found, which is interesting because most likely the same mechanism underlies pathological deposits. In addition to drusen found in some familial macular degeneration, such Malattia Leventinese (also Doynsche honeycomb dystrophy ) and Sorsby fundus.

Therapy

According to the current state of medical science, there is no effective therapy against Druze. Although the Laserkoagulationstherapie like used in the 90's was able to show an impressive regressing soft drusen after laser coagulation, the risk of developing AMD, but not decreased. Patients with drusen is recommended according to the results of the AREDS study an prophylactic vitamin Supplemention with lutein and omega- 3 fatty acids. This reduces the risk of the occurrence of AMD significantly. In addition, a quarterly monitoring is recommended during the ophthalmologist to diagnose the occurrence of an AMD earliest possible can.