Aging Related Changes in the Retina

The human retina shows considerable age-related structural changes, particularly in its peripheral zones, although the macula and its fovea centralis are not spared. The aged retinal periphery is thinner (10-30 mm), containing a lesser number of rods and other nerve cell types. The aging-related loss of rods appears to be a slow process, beginning in the third and fourth decade, and may be related to accumulated damage due to physiological exposure to light (8-10). With aging rods, outer...

Rectangularization or Mortality Compression

The age pattern of human mortality can be characterized in various ways. Figure 4 shows the American mortality levels in 1900 and 1995 from three perspectives. The first panel shows death rates by age. These death rates are used to construct a life table, which describes the experience of a hypothetical cohort subject throughout its life to the death rates of a given year. Thus, the middle and last panels show the distribution of deaths and the proportion of survivors at each age among members...

Iris and Senile Miosis

The iris is a smooth muscular ring forming the pupil of the eye Fig. 2B . Contraction and dilation of the pupil during the light reflex changes the amount of light entering the eye and is also important in the accommodation reflex. In the elderly, the iris appears paler in the middle, mainly due to loss of pigmentation in the radial dilator muscles. With aging, there is a mild but constant increase in the density of collagen fibers in the iris stroma and noncellular perivascular zones. A...

Anterior Chamber and Vitreous Gel Humor

The anterior chamber and its fluid, the aqueous humor, occupy a space between the cornea and the lens (Fig. 2B). The size and volume of the eye's anterior chamber decrease with age, mainly due to thickening of the lens. This growth occasionally exerts pressure on the canal of Schlemm (Fig. 2B), an outflow channel at the junction between the iris and the cornea, causing decreased flow and increased pressure intraocular pressure (IOP) of the aqueous humor. In normal aging, the increase in IOP is...