Findings From the 15-Year Follow-up of an Australian Cohort
Early age-related macular degeneration (AMD) is characterized by the presence of drusen and retinal pigmentary abnormalities.1,2 Drusen vary in size (diameter range, ≤63 to ≥250 μm) and type (hard, soft, distinct, and indistinct). Pigmentary abnormalities include clusters of pigment granules within the sensory retina (increased pigmentation) and sharply demarcated areas of retinal pigment epithelium (RPE) depigmentation.
The international classification and grading system for AMD categorizes medium drusen as intermediate soft drusen, defined as drusen with a maximum diameter of 63 to less than 125 μm, larger than the maximum diameter of hard drusen (‹63 μm) but smaller than the minimum diameter of large soft drusen (≥ 125 μm).1 A similar definition of this drusen type was used by the Age-Related Eye Disease Study2 and clinical classification system,3 categorized as medium drusen. urthermore, the Wisconsin Age-Related Maculopathy Grading System4 defines medium drusen by the maximum diameter, although the categorization of medium drusen is not used. In this study, we describe this type of drusen as medium drusen.
Despite recent interest in medium drusen and their inclusion in AMD incidence studies,5,6 knowledge of the associated risk factors and the progression of medium drusen is limited. Medium drusen have been underrepresented in studies3,7-9 compared with large drusen, soft drusen, and pigmentary lesions. In this study, we aimed to assess the 15-year incidence and progression of medium drusen in an older Australian cohort, as well as associations between common AMD risk factors and the development and progression of medium drusen.