Macular degeneration is known to be a bilateral disease. This study set out to determine the symmetry of phenotype between eyes of patients with bilateral early AMD (or drusen) or late-stage AMD. This may be important information when considering the likelihood of anti-VEGF treatment.

This prospective, observational, cross-sectional study graded the color fundus photographs of both eyes of 1,114 Caucasian patients with either early or late-stage AMD. Patients were recruited from a tertiary referral UK population. The main outcomes were phenotype, comparison of number, type and overall area of drusen in early AMD and symmetry of late AMD.

The overall agreement of phenotype in the entire cohort of patients was 53%, kappa statistic (κ)=0.31, (95% CI = 0.27–0.36). Within this group, a total of 271 patients were identified with bilateral soft and hard drusen (early AMD). Symmetry of phenotype within this group was high in terms of total of area of drusen (agreement = 79%, weighted κ = 0.75) and number of drusen. In those with bilateral geographic atrophy (GA), symmetry between area of GA was moderate (agreement 72%, weighted κ = 0.54), and in those with bilateral neovascular disease (choroidal neovascularization or pigment epithelial detachment), symmetry was poor (agreement 45%, weighted κ = 0.16). Out of the entire cohort, 62% (n = 688) had neovascular disease in at least one eye and 37.5% of these had bilateral disease.

The observed symmetry of phenotype between eyes with drusen appears to reduce in GA and neovascular forms of AMD. Overall, 53% of the cohort had symmetrical disease in terms of phenotype, 23% had neovascular disease in both eyes, 9.3% had GA in both eyes, and 39% of patients had neovascular disease in one eye and non-neovascular disease in the other. This may have implications for the potential need for anti-VEGF treatment of AMD in second eye involvement.