Purpose: To determine age-related macular degeneration (AMD) phenotypes associated with mutually exclusive homozygotic risk variants in rs1061170 (CFH) and rs11200638 (HTRA1).
Methods: Nested case-control study of 2,982 eyes (2,129 control, 809 drusen ≥125 μm, 44 advanced AMD) homozygous for CFH [TT or CC] and HTRA1 [GG or AA] were analyzed using logistic regression and generalized estimating equations specifically regards to homozygous risk variants in one but homozygous no-risk in the other gene.
Results: In early AMD, [CFH HTRA1] and [CFH HTRA1] were associated with central drusen (odds ratio [95% confidence interval] = 4.13 [2.97-5.73] and 3.65 [1.88-7.09], respectively). However, only [CFH HTRA1] was associated with central drusen occupying ≥50% area (13.9 [2.97-64.7]). In advanced AMD, [CFH HTRA1] was associated with geographic atrophy (4.04 [1.57-10.4]), whereas [CFH HTRA1] was associated with neovascular AMD (36.5 [8.3-160.9]). In doubly homozygous risk groups [CFH HTRA1], odds ratios were multiplicative.
Conclusion: Central but not peripheral drusen location was strongly associated with both [CFH HTRA1] and [CFH HTRA1]. Only [CFH HTRA1] was significantly associated with increased central drusen area.