Human Bruch's Membrane: Regional and Age-Related Alterations

ABSTRACT

Changes in the thickness and composition of Bruch's membrane with aging have been described by several observers and related to the development of macular with advancing ageby region, comparing the macular area with more peripheral areas. In the younger (less than. 50 years) eyes we studied, the thickness of macular Bruch's membrane was about equal to that of peripheral Bruch's membrane. With aging, however, the thickness of Bruch's membrane was greater in the periphery than the macula. With increasing age, Bruch's membrane increased in basophilic reaction, PAS positivity and the detectable sialomucin fraction. In the macular region, but not in more peripheral regions, there is a preferential thickening of the interchoriocapillaris "teeth" of Bruch's degeneration by some. Using a combination of histochemical and electronmicroscopic techniques, we have examined the state of Bruch's membrane membrane material. By electronmicroscopy, in older eyes, the elastin layer of Bruch's membrane appears fragmented, while, in the periphery, it is continuous and resembles that of younger eyes. In summary, Bruch's membrane exhibits little regional difference in thickness in younger eyes, but the macular region becomes relatively thinner than more peripheral regions in older eyes. With advancing age, the deposition of extracellular matrix materials in appatite and fragmentation of the elastin layer is dramatically more prominent in the macular region than in the periphery. This regional variation may be related, at least in part, to some aspects of macular degeneration.