Age-related Bruch's membrane change: a clinical study of the relative role of heredity and environment

For many years there has been controversy concerning the role of genetic influences in the pathogenesis of age-related macular disease. It is widely believed that the lesions causing visual loss occur in response to age-related changes in Bruch's membrane which are recognised clinically as drusen. In this study the density, size, and confluence of drusen as shown on colour photographs were compared in eyes of 50 spouses and 53 sibling pairs ascertained during a prospective study of age-related macular disease. Concordance between pairs of drusen--number, size, and density-were determined by kappa statistic and chi 2 test for trend. Drusen were absent in one sibling and 26 spouses of patients. There was a trend towards concordance of drusen characteristics between siblings but not between spouses, although the difference achieved 5% significance only for the number and density of drusen in the central macula. The difference of concordance between the probands and spouses and the probands and siblings was significant for all characteristics. These findings support the belief that genetic factors influence age-related changes in Bruch's membrane. They also imply that environmental factors are less important or alternatively that the environmental variation between households included in our study was not great enough to be evident.