Subretinal Drusenoid Deposits
Subretinal drusenoid deposits (SDDs), also known as reticular pseudodrusen, are aggregations of material that exist inside the retinal pigment epithelium (RPE). These deposits may penetrate internally through the ellipsoid zone (EZ).
SDDs are associated with type 3 neovascularization, outer retinal atrophy, and progression to geographic atrophy.
Often regression of SDDs may result in the development of outer retinal atrophy.
Occurs most commonly in advanced age groups. These SDDs are frequently associated with age-related macular degeneration (AMD) and age-related choroidal atrophy.
SDDs appear on optical coherence tomography (OCT) imaging as small elevations of material resting on top of the RPE. These accumulations are often isoreflective with the RPE and can be fairly subtle on imaging. This is in contrast to drusen which are under the RPE but above the Bruch membrane (see Chapter 21).
On OCT imaging, SDDs may be accompanied with EZ loss around the peak of the material deposit and also may be associated with outer retinal thinning.
Other concurrent associated signs may also be noted including peripapillary atrophy and choroidal thinning.
Choroidal neovascularization and geographic atrophy may also be associated with the presence of SDDs.
Compared to conventional drusen, SDDs of the same size demonstrate increased flow voids/nonperfusion within the choriocapillaris, providing a possible mechanistic explanation for worse visual deficits in AMD patients with SDDs compared to those without.
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