Retinal
aging and disease
Mike Boulton (UK-Cardiff)
Department of
Optometry and Vision Sciences, Cardiff University, Redwood Building, King
Edward VII Avenue, Cardiff, CF10 3NB, UK
The association
between natural ageing changes to the retina and age-related disease is
complex. It is evident that many of these age-related changes are manifest
preceding the onset of age-related maculopathy. Furthermore, it is becoming
clear that ageing is a combination of both genetic and environmental factors
which, in certain individuals may predispose disease. While age-related
changes including abnormal morphology, cell loss, thinning, gliosis and
alterations in macular pigment are seen in the neural retina the most
prominent age-related changes are observed in the retinal pigment epithelium
(RPE) and Bruch's membrane. The ageing characteristics of the RPE suggest
that in addition to cell loss, pleomorphic changes and loss of intact
melanin granules, significant metabolic changes occur resulting, at least
in part, from the intracellular accumulation of lipofuscin. This pigment
has been shown to be extremely phototoxic and has been linked to oxidative
changes, some leading to cell death. This coupled with an age-related
decline in antioxidant activity makes the aged RPE particularly succeptible
to oxidative stress. Major age-related changes are also associated with
Bruch's membrane. These include the appearance of Drusen, the formation
of basal laminar deposits and accumulation of lipid. These changes can
have a number of detrimental effects including loss of hydraulic conductivity,
a decrease in RPE function, increased fragility of Bruch's membrane allowing
choroidal vessels to enter the retina and an accumulation of angiogenic
factors. While the etiology of age-related macular degeneration is complex
and is as yet unresolved, it is likely that accelerated ageing-like changes
in the RPE and Bruch's membrane play a fundamental role in the development
of this debilitating condition.