Publisher's Synopsis
Senile cataract is a highly prevalent age-related disease accounting for 50% of blindness worldwide. In developed countries 15% of the population over the age of 50 years will be confronted with senile cataract and will need surgical intervention to restore `normal' vision; nowadays in the form of extracapsular cataract extraction and implantation of an artificial lens.;Because of the high prevalence and increased life expectancy, the costs of cataract extractions and of monitoring and treatment of postoperative complications will become a serious threat to health care budgets even in western countries. Understanding the causes and risk factors of age-related lens disturbances could give clues for delaying or preventing this highly prevalent disease.;Ageing is accompanied by accumulation of chromophores and aggregation of crystallins to high molecular weight molecules mainly in the lens nucleus. This leads to increased light scatter and diminished transparency. Nuclear changes are slowly progressing and, in very advanced stages, hamper sight to such an extent as to necessitate surgical removal of cataract. The major reasons for urgent surgical intervention are cortical or posterior subcapsular opacification, i.e. loss of transparency at the level of the outer layers of the lens, which can be associated with nuclear turbidity.;A characteristic of cortical cataracts is that the integrity of the lens fibers is disturbed due to derangement of the membranes limiting the lens fibers. Epithelial and fiber-limiting membranes are, like all cell membranes, very complex entities consisting of a phospholipid/cholesterol bilayer in which specific proteins are incorporated. These membrane-intrinsic proteins represent channels, pores and junctions. Furthermore crystallins, a variety of cytoskeletal proteins and calcium-binding proteins are associated with the membranes.;The interaction of these proteins with the phospholipid bilayer per se regulates the proper electrophysiological functioning of the membrane and thus the fine tuning of the homeostasis of ions. The lens-specific electro-physiological functions of the channels and pores, the association of crystallins and cytoskeletal proteins with membranes, the precise physiological role of junctional proteins and the exceptionally high cholesterol content of lens membranes are the ultimate relevance to understanding the pathological processes leading to vision-impairing cataracts.
