Inflammation in common eye disease

Inflammation is a part of the immune response and, because of this, is a common element in a number of clinical conditions. Many of these general conditions are connected in turn to ocular ones.

This article discusses these connections, and how, in addition to treatments, lifestyle changes in the form of good diet may play a part in controlling inflammation. Inflammatory ocular conditions are summarised in Table 1.

The immune system

The immune system comprises coordinated components that combat infection by hostile pathogens, which have to be differentiated from the friendly commensal bacteria in the body – for instance the trillions of bacteria in the alimentary tract that help us to digest our food. The immune system divides broadly into innate and adaptive systems. The innate system is active against all cells not recognised as ‘self’ or ‘friendly’ on the basis of previously available information. It is a ‘fast response’ system and relatively unspecific in its response, recruiting white blood cells such as neutrophils and macrophages to the affected site. These cells engulf the foreign organism and produce reactive oxygen species such as superoxidases and hydrogen peroxide to destroy them. The adaptive system on the other hand ‘learns’ about foreign invaders through contact with them, and then manufactures a response specific with that invader or antigen. This is largely driven by lymphocytes called T-cells, which carry specific receptors for the antigen. Because the acquired response requires exposure, learning and manufacturing to become effective, it is slower to activate. Once the invader has been identified and eliminated, a small number of ‘memory cells’ are retained in the body for a considerable time. These can respond very much more quickly to a second invasion by the same hostile organism. This mechanism is the basis of immunisation, in which an attenuated or dead form of the invader is introduced into the body to provoke a response, and establish the presence of the memory cells.