From the Guidelines
Drusen are yellow lesions at the level of the basement membrane of the retinal pigment epithelium (RPE), and are considered the ophthalmoscopic and histologic hallmark of age-related macular degeneration (AMD) 1.
Characteristics of Drusen
- They are classified based on their size, with small drusen being less than 63 μm in diameter, intermediate drusen being greater than or equal to 63 and less than or equal to 125 μm, and large drusen being greater than 125 μm in diameter 1.
- Drusen may also be classified as soft if they have ill-defined edges 1.
Clinical Significance of Drusen
- The presence of drusen is a key feature of AMD, and their size and number can be used to assess the risk of progression to advanced AMD 1.
- Large drusen (≥125 μm) are considered a high-risk feature for AMD, and individuals with these lesions should be considered for preventive measures such as nutritional supplements 1.
- The prevalence and incidence of drusen increase with age, and other risk factors such as smoking and family history can also contribute to their development 1.
From the Research
Definition and Composition of Drusen
- Drusen are extracellular material considered a precursor lesion to advanced age-related macular degeneration (AMD), located either on the retinal pigment epithelium (RPE) or the sub-RPE 2
- They contain various proteins associated with inflammation and lipids 2
- Drusen are subretinal pigment epithelial deposits that are characteristic of but not uniquely associated with age-related macular degeneration (AMD) 3
- The molecular composition of drusen includes cellular remnants and debris derived from degenerate RPE cells, which become sequestered between the RPE basal lamina and Bruch's membrane 4
Types of Drusen
- Hard drusen appear as small, punctate, yellow nodules and can precede the development of atrophic AMD 3
- Soft drusen appear as large (usually larger than 63 microm in diameter), pale yellow or grayish-white, dome-shaped elevations that can resemble localized serous RPE detachments 3
- Pachychoroid-associated drusen (pachydrusen) have been proposed as a distinct entity, with clinical findings accumulating as more attention is focused on drusen as well as pachychoroid diseases 2
Formation and Progression of Drusen
- The formation of drusen is thought to involve a chronic inflammatory stimulus, with the entrapped cellular debris becoming the target of encapsulation by a variety of inflammatory mediators 4
- The lifecycle of drusen varies depending on drusen type and size, with conventional drusen growing and aggregating/coalescing in the first stage, and regressing with or without showing RPE atrophy in the second stage 2
- Drusen characteristics correlated with progression to exudative maculopathy include drusen number (five or more), drusen size (larger than 63 microm in diameter), and confluence of drusen 3
- Calcified nodules in retinal drusen are associated with disease progression in age-related macular degeneration, with heterogeneous internal reflectivity within drusen (HIRD) on optical coherence tomography (OCT) images indicating an increased risk of progression to advanced AMD 5
Detection and Quantification of Drusen
- Multimodal imaging approaches enable the detection of drusen and drusenoid deposits, with Retro mode imaging allowing for a detailed detection of drusen phenotypes 6
- Quantitative data on subretinal drusenoid deposits (SDDs) can be obtained using en-face drusen and SDD area detection, with the topographic distribution of drusen analyzed according to a modified ETDRS grid 6