HTRA1 and age-related macular degeneration: The two most common genetic contributors to AMD are variants associated with a cluster of genes (complement factor H (CFH) – complement factor H-related (CFHR) 1 to 5) located on chromosome 1 (Chr1) and variants associated with age-related maculopathy susceptibility 2 (ARMS2) and high-temperature requirement factor A1 (HTRA1), two tightly-linked genes located on chromosome 10 (Chr10)6–8.