So called hyaline excrescences on the lamina vitrea (or Bruch’s membrane) have been a matter of debate for almost 150 years now. In 1877, Meyer speculates in Graefes Archiv 1 that “the very first beginning of drusen lies within Bruch’s membrane and is due to tiny refractive nodules or droplets excreted by the RPE”. He considered drusen as being associated not only with age, but also with inflammation and tumours and with the state of nutrition of the retina. It is amazing how little additional fundamental information concerning pathogenesis and evolution is available more than 100 years later.

Today, there is little doubt that sub-RPE (retinal pigment epithelium) deposits are somehow involved in the pathogenesis of age related macular degeneration (ARMD). However, the classical term “druse” is used by clinicians and histopathologists to describe a variety of excrescences on Bruch’s membrane that differ morphologically as well as biochemically and ophthalmoscopically. The more the information has been added to this subject, the more confusing the terminology has become.

There are three major methods of classifying extracellular sub-RPE material. Ophthalmoscopically one evaluates not only the clinical picture, but also the patient’s age, any family history, and additional investigations such as angiography with fluorescein or indocyanine green. Histopathologically, the tissue abnormalities are evaluated by conventional light or electron microscopy, and, thirdly, deposits can be investigated by various immunohistochemical or biochemical techniques. The common aim, of course, is to correlate all these findings in order to help our understanding of the development of ARMD …