Age-related components of Bruch's membrane in the human eye.

Age-related deposits within the inner and outer collagenous zones (ICZ/OCZ) of Bruch's membrane have been studied in normal aged human eyes. Electron microscopic examination of tissue from the macular region of 28 post-mortem eyes has shown that age-related deposits comprise mainly coated membrane-bound (CMB) bodies and their fragments. These bodies appear to be released from the RPE via the basal plasma membrane. Morphometric analysis of the average thickness and distribution of age-related deposits has demonstrated that as the thickness of the deposit increases with age, the major part is contained within the OCZ. The ICZ shows only a minimal increase in thickness during life. These results suggest that in the normal ageing eye the inner layers of Bruch's membrane (RPE basement membrane, ICZ and elastic layer) permit an unimpeded flow of CMB bodies from the RPE through to the OCZ.