C3 and age-related macular degeneration: Even if some of these relationships between these genes/loci and AMD are incompletely understood, their comprehensive consideration indicates, once again, that complement-related polymorphic alleles are able to increase (CFH, C3, CFI, and CFHR-2-4-5) or reduce (CFB, C2, and CFHR-1-3) AMD risk, representing a central key point on which the evidences of the high heritability of AMD are based [23, 106, 111].