In addition to complement factors, an SNP (rs11200638) in the promoter region, as well as two synonymous SNPs (rs2293870 G>C or T, rs1049331 C>T), in high temperature requirement protein A1 (HTRA1), which encodes a secreted serine protease, have also been confirmed as major genetic risk factors of AMD and estimated to present a population attributable risk of ~50% [61,62,63]. Here, HTRA1 is linked to age-related macular degeneration.