Retinal Structure and Organization

In this section we shall be concerned with the peripheral mechanisms in the visual process. When light strikes the retina, physical and chemical changes are induced that lead eventually to a discharge of electrical impulses in the optic nerve fibres. The ‘messages’ in these nerve fibres are a record of the events taking place in the retina; because of the variety of sensations evoked by visual stimuli, these records must be of almost fantastic complexity when even a simple image is formed on the retina. The aim of investigators in this field of eye physiology is to disentangle the skein; their approaches are various but may be classed generally as psychophysical, chemical, and electrophysiological. Remarkable progress has been made, especially in recent years, but there is still a long way to go before anything approaching an exact picture of the retinal processes can be elaborated. The following description is designed more to show the modes of approach to the various problems than to present a theoretical picture of the ‘mechanism of vision’.