This classification encompasses the shape of the RPE elevation (convex, ie, dome-shaped; concave, ie, pointed; or saw-toothed), the reflectivity of the druse (low, medium, or high, in relation to the photoreceptor layer), the homogeneity of the druse's content (homogeneous reflectivity, inhomogeneous with central core/focus of hyperreflectivity and inhomogeneous without a central core), and the presence or absence of hyperreflective foci above the druse.
Source: wiktionary