Extramacular drusen are highly associated with age-related macular degeneration, but not with CFH and ARMS2 genotypes

To evaluate the association of extramacular drusen (EMD) with age-related macular degeneration (AMD) and with complement factor H (CFH rs1061170) and age-related maculopathy susceptibility 2 (ARMS2 rs10490924) polymorphisms in individuals with and without AMD.

In this case-control study, AMD staging was performed in 622 individuals. EMD were defined as ≥10 drusen (including ≥1 intermediate drusen) outside the Early Treatment of Diabetic Retinopathy Study Grid within field 2. Genotype associations for CFH and ARMS2 variants were assessed using logistic regression analysis.

EMD (n=213) showed a strong association with AMD (OR=3.85; p=1.66×10(-13)). AMD (n=316) was strongly associated with CFH (p=1.78×10(-7)) and ARMS2 genotypes (p=1.67×10(-8)). After adjustment for AMD, age and gender, EMD were neither associated with CFH (p=0.11) nor with ARMS2 (p=0.45) genotypes. In individuals without AMD, the groups with and without EMD showed no differences regarding both genetic variants.

The strong association between drusen within and outside of the macula suggests a common pathogenesis. However, EMD were not AMD-independently associated with CFH or ARMS2 genotypes. Our results indicate that patients without AMD but with EMD can serve as controls in studies evaluating AMD risk factors. Further studies are required to elucidate the aetiology and clinical relevance of EMD.