Perhaps the most common type of ocular ailment resulting in diminution of visual acuity in older persons is senile cataract, a condition characterized by opacification of the normally transparent lens without any direct local or constitutional cause.
The lens occupies a very unique position in the economy of the body. It is entirely self-contained, having neither vascular nor nervous connections, and is surrounded by the aqueous humor, on which it is almost wholly dependent for those processes of metabolic exchange with which its vitality and continuing clarity are so intimately connected. The growth of the lens is normally continuous from early fetal life until somatic death and its crystal clearness is maintained normally.
Many theories have been advanced but relatively little is known concerning the mechanism of pathogenesis of cataract.1,2 The lens is considered to grow to maturity and then to undergo physicochemical changes associated with senescence. These include
GREEN H, SOLOMON SA. The Effect of Age upon Lens Metabolism. AMA Arch Ophthalmol. 1957;58(1):23-36. doi:10.1001/archopht.1957.00940010035004