Drusen bodies are extracellular deposits of lipids, proteins, and cellular debris which are found within the layers of the retina and appear as small, yellow deposits on dilated eye exams. Specifically, drusen reside between the basal lamina of the retinal pigment epithelium (RPE) and the inner layer of the Bruch membrane (BM). These sub-RPE deposits are seen with the progression of normal aging; however, depending on the size, number, location, and type of drusen involved, they can be associated with increased risk of developing age-related macular degeneration (AMD).
Although there is speculation regarding the exact mechanisms involved in the formation of drusen bodies, there is a general consensus that deposits are lipid and protein-rich and are driven by age-related biochemical changes. Current evidence suggests that drusen bodies are composed of cholesterol-containing lipid droplets forming the core structure upon which hydroxyapatite (HAP) spherules precipitate. These HAP spherules facilitate protein deposition to their surface which results in an oligomerization process ultimately forming the sub-RPE deposits. One focus of the study has been the proteins involved in the formation of drusen, and many different proteins have been implicated in this process. Some of the most common proteins involved include amyloid-beta, apolipoproteins, vitronectin, and complement proteins.