After controlling for the effect of each SNP with respect to the other, it was evident that this joint effect was due to the significant assocation of SNP rs2014307 with AMD risk, as the p value was greater for the PLEKHA1/HTRA1 SNP (P < 10-6) than it was for CFH SNP rs10801575, (P < 10-4). This evidence concerns the gene PLEKHA1 and age-related macular degeneration.