(PROTEIN) WATER MOLECULE AMINO GROUP

C H A P T E R 1 0
Ocular Biochemical
Degradation
AGING AND PATHOLOGICAL PROCESSES
This chapter is a sojourn into biochemical processes that
degrade the eye. Some of these processes are a natural result
of aging and some occur as a result of an accidental occurrence
or a disease. For example, as a part of the aging process, the normal gel
structure of the vitreous slowly is converted to a liquid. This conversion
may ultimately result in a detached retina. Another example occurs in
industrial settings when a strong alkali, such as sodium hydroxide that
is used and is accidentally spilled on a worker’s eyes resulting in
opacification of the cornea.
There is great interest in being able to describe and find ways of
curing corneal wounding of all kinds as a way of avoiding unnecessary
corneal transplantation. Here, only a selected number of the biochemical
processes of degradation will be discussed. Some other degradative
processes have already been described in previous chapters.
Cellular Apoptosis
Apoptosis (from the Greek: αποπτοσις—a falling down or degradation)
is a form of programmed cell death. In the eye, it occurs in photoreceptor
cells as a result of excessive light exposure (Wenzel et al., 2001); in
cultured conjunctival cells placed in contact with ocular preservatives
(Debbasch et al., 2001); and in corneal epithelial and keratocytic cells
after wounding (Wilson, Kim, 1998).
In general there are two forms of cell death that are acknowledged
by scientists: necrosis and apoptosis (Cameron and Feuer, 2000).
Necrosis (Greek: νεκροσις—a killing) usually occurs as a result of
several conditions including: hypoxia, ischemia, tissue trauma, and complement-mediated
cell damage. It is a process in which the cell initially
appears swollen, the cytoplasm is reddish when stained with the dye
eosin, and the nuclei’s chromatin (genomic material) becomes condensed
or clumped. Later the chromatin vanishes and the cells are consumed by
phagocytes (see inflammatory reaction in Chapter 9). Biochemically, all
the cell membranes become indiscriminately permeable as the various
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